Feature: nim book command to produce documentation from Nim-flavored Markdown (#26139)

This PR adds a new Nim compiler command and introduces some improvements to the docgen suite in general. 1. Adds `nim book`, the new command that takes a directory with Markdown/ReST files and generates a navigatable, searchable, Nim-first documentation site. 2. Refactors the default nimdoc.cfg, specifically the part marked with "needs to be refactored." Code duplication was removed, new overridable variables were added, quirky logic with the "Group by" switch display was fixed. Here's a live demo of a `nim book` produced book: https://moigagoo.github.io/nim-chronos/ The original mdBook-powered version: https://status-im.github.io/nim-chronos/ Related to this PR but valuable on their own: 1. `.. include::` directive has received several improvements: - You can now include code from line to line, merged: https://github.com/nim-lang/Nim/pull/26130 - You can now include code with syntax highlighting, merged: https://github.com/nim-lang/Nim/pull/26146 2. `.. admonition::` directive (and its derivatives like `warning`, `error`, etc.) got new useful functions: - You can now set a title to your admonitions, open: https://github.com/nim-lang/Nim/pull/26159 - You can make admonitions collapsible (useful when you need to include a large chunk if code), open: https://github.com/nim-lang/Nim/pull/26159
2026-09-17 10:34:53 +00:00 · 2026-09-03 15:45:58 +04:00
parent e927887b7e
commit 4cf3a95554
57 changed files with 1948 additions and 276 deletions
--- a/compiler/commands.nim
+++ b/compiler/commands.nim
@@ -491,6 +491,7 @@ proc parseCommand*(command: string): Command =
  of "e": cmdNimscript
  of "doc0": cmdDoc0
  of "doc2", "doc": cmdDoc
+  of "book": cmdBook
  of "doc2tex": cmdDoc2tex
  of "rst2html": cmdRst2html
  of "md2tex": cmdMd2tex
--- a/compiler/docgen.nim
+++ b/compiler/docgen.nim
@@ -24,7 +24,7 @@ import
 import packages/docutils/rstast except FileIndex, TLineInfo

 import std/[os, strutils, strtabs, algorithm, json, osproc, tables, intsets, xmltree, sequtils]
-from std/uri import encodeUrl
+from std/uri import encodeUrl, parseUri, isAbsolute
 from nodejs import findNodeJs

 when defined(nimPreviewSlimSystem):
@@ -76,6 +76,19 @@ type
    json: JsonNode
    rst: PRstNode
    rstField: string
+  NavItemKind = enum
+    niLink
+    niLabel
+    niHeading
+  NavItem = object
+    ## Navigation entry for the sidebar navigation.
+    title: string
+    case kind: NavItemKind
+    of niLink:
+      dest: string
+    else:
+      discard
+    sons: seq[NavItem]
  TDocumentor = object of rstgen.RstGenerator
    modDescPre: ItemPre   # module description, not finalized
    modDescFinal: string  # module description, after RST pass 2 and rendering
@@ -1726,10 +1739,19 @@ proc genOutFile(d: PDoc, groupedToc = false): string =
    dispA(d.conf, subtitle, "<h2 class=\"subtitle\">$1</h2>",
        "\\\\\\vspace{0.5em}\\large $1", [esc(d.target, d.meta[metaSubtitle])])

+  let theIndexHref = relLink(d.conf.outDir, d.destFile.AbsoluteFile, theindexFname.RelativeFile)
+  let indexLink = getConfigVar(d.conf, "doc.body_toc_indexlink") % ["theindexhref", theIndexHref]
+  let navLinks = getConfigVar(d.conf, "doc.body_toc_navlinks", "")
+  let globalLinks = getConfigVar(d.conf, "doc.body_toc_globallinks") % [
+      "body_toc_navlinks", navLinks,
+      "body_toc_indexlink", indexLink,
+      "theindexhref", theIndexHref] # added because the `boot` branch uses `$theindexhref` directly
+  let searchBox = getConfigVar(d.conf, "doc.body_toc_searchbox")
+  let themeSelect = getConfigVar(d.conf, "doc.body_toc_themeselect")
  var groupsection = getConfigVar(d.conf, "doc.body_toc_groupsection")
-  let bodyname = if d.hasToc and not d.standaloneDoc and not d.conf.isLatexCmd:
+  let bodyname = if d.hasToc and d.standaloneDoc and not d.conf.isLatexCmd:
                   groupsection.setLen 0
-                   "doc.body_toc_group"
+                   "doc.body_toc"
                 elif d.hasToc: "doc.body_toc"
                 else: "doc.body_no_toc"
  let seeSrc = genSeeSrc(d, d.filename, 1)
@@ -1738,9 +1760,11 @@ proc genOutFile(d: PDoc, groupedToc = false): string =
      "tableofcontents", toc, "moduledesc", d.modDescFinal, "date", getDateStr(),
      "time", getClockStr(), "content", code,
      "deprecationMsg", d.modDeprecationMsg,
-      "theindexhref", relLink(d.conf.outDir, d.destFile.AbsoluteFile,
-                              theindexFname.RelativeFile),
-      "body_toc_groupsection", groupsection, "seeSrc", seeSrc]
+      "body_toc_groupsection", groupsection,
+      "body_toc_globallinks", globalLinks,
+      "body_toc_searchbox", searchBox,
+      "body_toc_themeselect", themeSelect,
+      "seeSrc", seeSrc]
  if optCompileOnly notin d.conf.globalOptions:
    # XXX what is this hack doing here? 'optCompileOnly' means raw output!?
    code = getConfigVar(d.conf, "doc.file") % [
@@ -1852,10 +1876,15 @@ proc commandDoc*(cache: IdentCache, conf: ConfigRef) =

 proc commandRstAux(cache: IdentCache, conf: ConfigRef;
                   filename: AbsoluteFile, outExt: string,
-                   preferMarkdown: bool) =
-  var filen = addFileExt(filename, "txt")
+                   preferMarkdown: bool, hasToc=false, addTxtExt=true) =
+  let filen =
+    if addTxtExt:
+      filename
+    else:
+      addFileExt(filename, "txt")
+
  var d = newDocumentor(filen, cache, conf, outExt, standaloneDoc = true,
-                        preferMarkdown = preferMarkdown, hasToc = false)
+                        preferMarkdown = preferMarkdown, hasToc = hasToc)
  try:
    let rst = parseRst(readFile(filen.string),
                      line=LineRstInit, column=ColRstInit,
@@ -1926,10 +1955,11 @@ proc commandTags*(cache: IdentCache, conf: ConfigRef) =
    except IOError:
      rawMessage(conf, errCannotOpenFile, filename.string)

-proc commandBuildIndex*(conf: ConfigRef, dir: string, outFile = RelativeFile"") =
+proc commandBuildIndex*(conf: ConfigRef, dir: string, outFile = RelativeFile"",
+                        exclCode = false, inclHeaders = false) =
  if optGenIndexOnly in conf.globalOptions:
    return
-  var content = mergeIndexes(dir)
+  var content = mergeIndexes(dir, exclCode, inclHeaders)

  var outFile = outFile
  if outFile.isEmpty: outFile = theindexFname.RelativeFile.changeFileExt("")
@@ -1962,3 +1992,127 @@ proc commandBuildIndexJson*(conf: ConfigRef, dir: string, outFile = RelativeFile
    writeFile(filename, $body)
  except IOError:
    rawMessage(conf, errCannotOpenFile, filename.string)
+
+proc commandBook*(cache: IdentCache, conf: ConfigRef) =
+  let bookDir = conf.projectFull.string
+  conf.projectPath = AbsoluteDir(bookDir) # set bookDir to be the documentation root,
+                                          # so that we don't end up with our output in `<outDir>/<bookDir>`;
+                                          # we want it in `<outDir>`
+  let summaryFilePath = bookDir / "SUMMARY.md"
+  if not fileExists(summaryFilePath):
+    rawMessage(conf, errCannotOpenFile, summaryFilePath)
+    return
+  let summaryFile = AbsoluteFile(summaryFilePath)
+  var d = newDocumentor(summaryFile, cache, conf, HtmlExt,
+                        standaloneDoc = true, preferMarkdown = true, hasToc = true)
+  let rst = parseRst(readFile(summaryFile.string),
+                    line=LineRstInit, column=ColRstInit, conf, d.sharedState)
+  var navTree: seq[NavItem] = @[]
+
+  proc traverseBulletList(list: PRstNode): seq[NavItem] =
+    ## Recursively go through a bullet list and generate a nav subtree from it.
+    result = @[]
+    for node in list.sons:
+      let inner = node.sons[0]
+      let innerBody = inner.sons[0]
+      var item =
+        case innerBody.kind
+        of rnHyperlink:
+          NavItem(title: innerBody.sons[0].text, kind: niLink, dest:innerBody.sons[1].text)
+        of rnLeaf:
+          NavItem(title: inner.renderRstToText(), kind: niLabel)
+        else:
+          NavItem()
+
+      if len(node.sons) > 1:
+        item.sons = traverseBulletList(node.sons[1])
+
+      result.add(item)
+
+  proc parseSummary(root: PRstNode): seq[NavItem] =
+    ## Parse the root node from the summary file and generate the nav tree.
+    result = @[]
+    let nodes = if root.kind == rnInner: root.sons else: @[root]
+    for node in nodes:
+      case node.kind
+      of rnMarkdownHeadline:
+        let title = node.renderRstToText()
+        result.add(NavItem(title: title, kind: niHeading))
+      of rnBulletList:
+        result &= traverseBulletList(node)
+      else:
+        discard
+
+  proc isGlobalUri(path: string): bool =
+    parseUri(path).isAbsolute()
+
+  proc existsSrcFile(path: string): bool =
+    not path.isGlobalUri and fileExists(bookDir / path)
+
+  proc generateNavLinks(navSubTree: seq[NavItem], destFile: AbsoluteFile,
+                        nested=false): tuple[navLinks: string, hasCurrentPage: bool] =
+    ## Generate the navigation links for the sidebar.
+    ## Each page has a different set of those, adjusted for relative location.
+    let tocClassName =
+      if nested: "nested-toc-section"
+      else: "simple-toc-section"
+    var navLinks = """<ul class="simple $#">""" % [tocClassName]
+    var containsCurrent = false
+    for item in navSubTree:
+      var isCurrent = false
+      let content =
+        case item.kind
+        of niHeading:
+          """<strong>$#</strong>""" % [esc(outHtml, item.title)]
+        of niLabel:
+          esc(outHtml, item.title)
+        of niLink:
+          let href =
+            if item.dest.existsSrcFile():
+              relLink(conf.outDir, destFile, RelativeFile(item.dest.changeFileExt(HtmlExt)))
+            else:
+              item.dest
+          isCurrent =
+            not item.dest.isGlobalUri() and
+            destFile == getOutFile2(conf, presentationPath(conf, AbsoluteFile(bookDir / item.dest)), HtmlExt, false)
+          let cls =
+            if isCurrent: "current"
+            else: ""
+          """<a href="$#" class="$#">$#</a>""" % [href, cls, esc(outHtml, item.title)]
+      if len(item.sons) == 0:
+        navLinks &= """<li>$#</li>""" % [content]
+      else:
+        let (sonsNavLinks, sonsContainCurrent) = generateNavLinks(item.sons, destFile, nested=true)
+        let unfold = isCurrent or sonsContainCurrent
+        let openAttr = if unfold: " open" else: ""
+        navLinks &= """<li><details$#><summary>$#</summary>$#</details></li>""" %
+          [openAttr, content, sonsNavLinks]
+        containsCurrent = containsCurrent or unfold
+      containsCurrent = containsCurrent or isCurrent
+    navLinks &= """</ul>"""
+    result = (navLinks, containsCurrent)
+
+  proc generatePage(filename: AbsoluteFile) =
+    ## Generate an HTML page from a Markdown file.
+    conf.outFile = RelativeFile"" # reset to force path re-generation for each page
+    let destFile = getOutFile2(conf, presentationPath(conf, filename), HtmlExt, false)
+    let (navLinks, _) = generateNavLinks(navTree, destFile)
+    setConfigVar(conf, "doc.body_toc_navlinks", navLinks)
+    commandRstAux(cache, conf, filename, HtmlExt,
+                  preferMarkdown=true, hasToc=true, addTxtExt=false)
+
+  proc generatePages(navSubTree: seq[NavItem]) =
+    ## Generate all pages from the Markdown files listed in the summary file.
+    for item in navSubTree:
+      if item.kind == niLink and not item.dest.isGlobalUri():
+        let pageFilePath = bookDir / item.dest
+        if fileExists(pageFilePath):
+          let pageFile = AbsoluteFile(pageFilePath)
+          generatePage(pageFile)
+        else:
+          rawMessage(conf, warnCannotOpenFile, pageFilePath)
+      generatePages(item.sons)
+
+  setConfigVar(conf, "doc.body_toc_groupsection", "") # we don't need "Group by" section in standalone docs
+  navTree = parseSummary(rst)
+  generatePages(navTree)
--- a/compiler/main.nim
+++ b/compiler/main.nim
@@ -313,6 +313,7 @@ proc mainCommand*(graph: ModuleGraph) =

  ## command prepass
  if conf.cmd == cmdCrun: conf.globalOptions.incl {optRun, optUseNimcache}
+  if conf.cmd == cmdBook: conf.globalOptions.incl {optGenIndex}
  if conf.cmd notin cmdBackends + {cmdTcc}: customizeForBackend(backendC)
  if conf.outDir.isEmpty:
    # doc like commands can generate a lot of files (especially with --project)
@@ -321,7 +322,7 @@ proc mainCommand*(graph: ModuleGraph) =
              else: conf.projectPath
    if not ret.string.isAbsolute: # `AbsoluteDir` is not a real guarantee
      rawMessage(conf, errCannotOpenFile, ret.string & "/")
-    if conf.cmd in cmdDocLike + {cmdRst2html, cmdRst2tex, cmdMd2html, cmdMd2tex}:
+    if conf.cmd in cmdDocLike + {cmdRst2html, cmdRst2tex, cmdMd2html, cmdMd2tex, cmdBook}:
      ret = ret / htmldocsDir
    conf.outDir = ret

@@ -348,6 +349,11 @@ proc mainCommand*(graph: ModuleGraph) =
      commandDoc2(graph, HtmlExt)
      if optGenIndex in conf.globalOptions and optWholeProject in conf.globalOptions:
        commandBuildIndex(conf, $conf.outDir)
+  of cmdBook:
+    loadConfigs(DocConfig, cache, conf, graph.idgen)
+    conf.setNoteDefaults(warnCannotOpenFile, true)
+    commandBook(cache, conf)
+    commandBuildIndex(conf, $conf.outDir, exclCode = true, inclHeaders = true)
  of cmdRst2html, cmdMd2html:
    # XXX: why are warnings disabled by default for rst2html and rst2tex?
    for warn in rstWarnings:
--- a/compiler/options.nim
+++ b/compiler/options.nim
@@ -197,6 +197,7 @@ type
    cmdNimscript # evaluate nimscript
    cmdDoc0
    cmdDoc      # convert .nim doc comments to HTML
+    cmdBook # generate documentation site from a directory with Markdown files
    cmdDoc2tex  # convert .nim doc comments to LaTeX
    cmdRst2html # convert a reStructuredText file to HTML
    cmdRst2tex # convert a reStructuredText file to TeX
--- a/config/nimdoc.cfg
+++ b/config/nimdoc.cfg
@@ -127,36 +127,57 @@ doc.body_toc_groupsection = """
 </div>
 """

+doc.body_toc_themeselect = """
+<div class="theme-select-wrapper">
+  <label for="theme-select">Theme:&nbsp;</label>
+  <select id="theme-select" onchange="setTheme(this.value)">
+    <option value="auto">🌗 Match OS</option>
+    <option value="dark">🌑 Dark</option>
+    <option value="light">🌕 Light</option>
+  </select>
+</div>
+"""
+
+doc.body_toc_indexlink = """
+<ul class="simple">
+  <li><a id="indexLink" href="$theindexhref">Index</a></li>
+</ul>
+"""
+
+doc.body_toc_searchbox = """
+  <div id="searchInputDiv">
+  Search: <input type="search" id="searchInput" oninput="search()"/>
+</div>
+"""
+
@if boot:
-# This is enabled with the "boot" directive to generate
-# the compiler documentation.
-# As a user, tweak the block below instead.
-# You can add your own global-links entries
-doc.body_toc_group = """
+doc.body_toc_globallinks = """
+  <div id="global-links">
+  <ul class="simple-boot">
+    <li><a href="manual.html">Manual</a></li>
+    <li><a href="lib.html">Standard library</a></li>
+    <li><a id="indexLink" href="$theindexhref">Index</a></li>
+    <li><a href="compiler/$theindexhref">Compiler docs</a></li>
+    <li><a href="https://nim-lang.github.io/fusion/theindex.html">Fusion docs</a></li>
+    <li><a href="https://nim-lang.github.io/Nim/">devel</a>, <a href="https://nim-lang.org/documentation.html">stable</a></li>
+  </ul>
+</div>
+"""
+@else:
+doc.body_toc_globallinks= """
+<div id="global-links">
+  $body_toc_navlinks
+  $body_toc_indexlink
+</div>
+"""
+@end
+
+doc.body_toc = """
 <div class="row">
  <div class="three columns">
-    <div class="theme-select-wrapper">
-      <label for="theme-select">Theme:&nbsp;</label>
-      <select id="theme-select" onchange="setTheme(this.value)">
-        <option value="auto">🌗 Match OS</option>
-        <option value="dark">🌑 Dark</option>
-        <option value="light">🌕 Light</option>
-      </select>
-    </div>
-    <div id="global-links">
-      <ul class="simple-boot">
-        <li><a href="manual.html">Manual</a></li>
-        <li><a href="lib.html">Standard library</a></li>
-        <li> <a id="indexLink" href="$theindexhref">Index</a></li>
-        <li><a href="compiler/$theindexhref">Compiler docs</a></li>
-        <li><a href="https://nim-lang.github.io/fusion/theindex.html">Fusion docs</a></li>
-        <li><a href="https://nim-lang.github.io/Nim/">devel</a>, <a href="https://nim-lang.org/documentation.html">stable</a></li>
-      </ul>
-    </div>
-    <div id="searchInputDiv">
-      Search: <input type="search" id="searchInput"
-        oninput="search()" />
-    </div>
+    $body_toc_themeselect
+    $body_toc_globallinks
+    $body_toc_searchbox
    $body_toc_groupsection
    $tableofcontents
  </div>
@@ -170,49 +191,6 @@ doc.body_toc_group = """
 </div>
 """

-@else
-# keep in sink with other `doc.body_toc_group` or better, refactor
-doc.body_toc_group = """
-<div class="row">
-  <div class="three columns">
-    <div class="theme-select-wrapper">
-      <label for="theme-select">Theme:&nbsp;</label>
-      <select id="theme-select" onchange="setTheme(this.value)">
-        <option value="auto">🌗 Match OS</option>
-        <option value="dark">🌑 Dark</option>
-        <option value="light">🌕 Light</option>
-      </select>
-    </div>
-    <div id="global-links">
-      <ul class="simple">
-        <li><a id="indexLink" href="$theindexhref">Index</a></li>
-      </ul>
-    </div>
-    <div id="searchInputDiv">
-      Search: <input type="search" id="searchInput" oninput="search()"/>
-    </div>
-    <div>
-      Group by:
-      <select onchange="groupBy(this.value)">
-        <option value="section">Section</option>
-        <option value="type">Type</option>
-      </select>
-    </div>
-    $tableofcontents
-  </div>
-  <div class="nine columns" id="content">
-    $seeSrc
-    <div id="tocRoot"></div>
-    $deprecationMsg
-    <p class="module-desc">$moduledesc</p>
-    $content
-  </div>
-</div>
-"""
-@end
-
-doc.body_toc %= "${doc.body_toc_group}" # should only be used for boot
-
 doc.body_no_toc = """
 $moduledesc
 $content
--- a/doc/docgen.md
+++ b/doc/docgen.md
@@ -25,6 +25,7 @@ exported symbols (`*`), including procedures, types, and variables.
 command               output format
 ===================   ==============
 `nim doc`:cmd:        ``.html`` HTML
+`nim book`:cmd:       ``.html`` HTML
 `nim doc2tex`:cmd:    ``.tex`` LaTeX
 `nim jsondoc`:cmd:    ``.json`` JSON
 ===================   ==============
@@ -36,6 +37,8 @@ See [Nim-flavored Markdown and reStructuredText] document for the description
 of this feature and particularly section [Command line usage] for the full
 list of supported commands.

+You can also generate a full documentation site from a directory with [Nim-flavored Markdown and reStructuredText] files and `SUMMARY.md` using `nim book`:cmd:, similarly to how [mdBook](https://rust-lang.github.io/mdBook/) and other doc generators work.
+
 Quick start
 -----------

@@ -62,6 +65,12 @@ Generate HTML documentation for a whole project:
  # Use `--showNonExports` to show non-exported fields of an exported type.
  ```

+Generate a site from a directory of Markdown files and `SUMMARY.md`:
+
+  ```cmd
+  nim book <srcDir>
+  ```
+
 Documentation Comments
 ----------------------

@@ -179,6 +188,98 @@ Index (``.idx``) files are used for 2 different purposes:
   see [Buildindex command].


+Book Generator
+==============
+
+Nim ships with a complete book generator that lets you build sites from Markdown/reST files organized in folders.
+
+Powered by `nim doc`:cmd:, `nim book`:cmd: has all its features like built-in admonitions, code inclusion syntax, and checked Nim code references, but also offers `SUMMARY.md`-based source collection and navigation generation that should be familiar to [mdBook](https://rust-lang.github.io/mdBook/) users and simplify migration.
+
+Quickstart
+----------
+
+1. Create a directory for the book source, e.g `bookSrc`.
+2. Put a Markdown file in this directory, e.g. `welcome.md`:
+
+  ```markdown
+  # Welcome to Nim Book
+
+  This is the first paragraph.
+  ```
+
+3. Put a file called `SUMMARY.md` in the same directory. The file lists all your pages (one so far):
+
+  ```markdown
+  - [Welcome](./welcome.md)
+  ```
+
+4. Run `nim book`:cmd: with the book source directory:
+
+  ```cmd
+  $ nim book boorSrc
+  ```
+
+The docs will be generated in `htmldocs`, which is the default for `nim docs`:cmd:. You can customize the location with `--outDir:OUTDIR`:option:, just like for `nim doc`:cmd:.
+
+To see your book in the browser, serve `htmldocs` with any static server (e.g. `python3 -m http.server -d htmldocs/` ) and open the localhost location that it provides (e.g. http://localhost:8000). This way you'll have search working.
+
+To set the title for the page, use ``.. title::``:
+
+  ```markdown
+  .. title:: Welcome to Nim Book
+
+  # Part 1
+
+  This is the first paragraph.
+  ```
+
+To customize the way your page is listed in the sidebar navigation, set its link title in `SUMMARY.md`:
+
+  ```markdown
+  - [Intro](./welcome.md)
+  ```
+
+As your `SUMMARY.md` grows, you'll want to group the pages into sections. You can do that using nested bullet lists and headers:
+
+  ```markdown
+  - [Intro](./welcome.md)
+  - [Guides](./guides.md)                      <!-- This is page that is also a section header   -->
+    - [Dev Guide](./guides/dev.md)             <!-- These pages are rendered in a folded section -->
+    - [User Guide](./guides/user.md)
+
+  # References                                 <!-- Headers serve as visual separators           -->
+
+  - accounts                                   <!-- Section headers can be plain text            -->
+    - [Intro](./ref/accounts/intro.md)
+    - [Glossary](./ref/accounts/glossary.md)
+  - billing
+    - [Intro](./ref/billing/intro.md)
+    - [Glossary](./ref/billing/glossary.md)
+  ```
+
+Migrating from mdBook
+---------------------
+
+The easiest way to migrate to `nim book`:cmd: from mdBook is to feed the pre-cooked prompt to an LLM of your choice.
+
+.. note::
+  :title: Migrate from mdBook prompt
+  :collapsible: closed
+
+  .. include:: ./mdbookmigration.prompt
+    :literal:
+
+Or use the same prompt as a checklist to do the migration manually.
+
+Notes
+-----
+
+- if your docs won't build because an ``.idx`` file cannot be found, pre-build the indexes with `nim book --index:only bookSrc`:cmd: and then run `nim book bookSrc`:cmd: again
+- `nim book`:cmd: doesn't automatically copy assets from the source directory to the destination directory. The recommended pattern to work with images and other assets is to place them in a specialized directory (i.e. `bookSrc/img`) and copy it into `htmldocs/img` after build
+- for your readers' convenience, you can make a certain page your welcome page, i.e. opened by default when the reader opens your book; to do that, simply copy the desired page to ``index.html`` after build: `cp htmldocs/welcome.html htmldocs/index.html`
+- to add links to page source reading and editing, use the standard `--git.url`:option: and `--git.commit`:option: options: `nim book --git.url:https://github.com/owner/repo --git.commit:master bookSrc`:cmd:
+
+
 Document Types
 ==============

@@ -845,7 +946,7 @@ rstgen.html#setIndexTerm,RstGenerator,string,string,string,string,string)
 and `writeIndexFile() <rstgen.html#writeIndexFile,RstGenerator,string>`_ procs.
 The purpose of `idx` files is to hold the interesting symbols and their HTML
 references so they can be later concatenated into a big index file with
-[mergeIndexes()](rstgen.html#mergeIndexes,string).  This section documents
+[mergeIndexes()](rstgen.html#mergeIndexes,string,bool,bool).  This section documents
 the file format in detail.

 Index files are line-oriented and tab-separated (newline and tab characters
--- a/doc/markdown_rst.md
+++ b/doc/markdown_rst.md
@@ -42,17 +42,18 @@ the result to HTML [^html] or Latex [^latex].

 Full list of supported commands:

-===================   ======================   ============   ==============
-command               runs on...               input format   output format
-===================   ======================   ============   ==============
-`nim md2html`:cmd:    standalone md files      ``.md``        ``.html`` HTML
-`nim md2tex`:cmd:     same                     same           ``.tex`` LaTeX
-`nim rst2html`:cmd:   standalone rst files     ``.rst``       ``.html`` HTML
-`nim rst2tex`:cmd:    same                     same           ``.tex`` LaTeX
-`nim doc`:cmd:        documentation comments   ``.nim``       ``.html`` HTML
-`nim doc2tex`:cmd:    same                     same           ``.tex`` LaTeX
-`nim jsondoc`:cmd:    same                     same           ``.json`` JSON
-===================   ======================   ============   ==============
+===================   =======================   ============   ==============
+command               runs on...                input format   output format
+===================   =======================   ============   ==============
+`nim md2html`:cmd:    standalone md files       ``.md``        ``.html`` HTML
+`nim book`:cmd:       directory with md files   same           same
+`nim md2tex`:cmd:     same                      same           ``.tex`` LaTeX
+`nim rst2html`:cmd:   standalone rst files      ``.rst``       ``.html`` HTML
+`nim rst2tex`:cmd:    same                      same           ``.tex`` LaTeX
+`nim doc`:cmd:        documentation comments    ``.nim``       ``.html`` HTML
+`nim doc2tex`:cmd:    same                      same           ``.tex`` LaTeX
+`nim jsondoc`:cmd:    same                      same           ``.json`` JSON
+===================   =======================   ============   ==============


 Basic markup
@@ -95,6 +96,10 @@ Supported common RST/Markdown features:
    - ``include``
    - admonitions: "attention", "caution", "danger", "error", "hint",
      "important", "note", "tip", "warning", "admonition"
+      - ``:title:`` option sets custom title for an admonition,
+        otherwise its kind capitalized is used
+      - ``:collapsible:`` makes an admonition collapsible in HTML output
+        ``:collapsible: closed`` makes it closed by default
    - substitution definitions: `replace` and `image`
  + comments
 * inline markup
--- a/doc/mdbookmigration.prompt
+++ b/doc/mdbookmigration.prompt
@@ -0,0 +1,167 @@
+# Migrate an mdBook project to `nim book`
+
+Convert a Markdown documentation book (currently built with mdBook) into a
+`nim book` project. The book lives in a directory (call it `book/`) with a
+`SUMMARY.md` at its root, and the API docs (generated from `.nim` source via
+`nim doc --project --index:on`) live in a sibling `api/` directory that ends up
+at `<outdir>/api/`.
+
+## Context
+
+`nim book` is a Nim compiler command that turns a directory of Nim-flavored
+Markdown (`.md`) files into a static documentation site, using `SUMMARY.md` for
+structure/navigation. It supports:
+
+- `.. include::` with `:code:` (syntax-highlighted code inclusion),
+  `:start-after:`/`:end-before:` (selective inclusion), and `:literal:` (plain).
+- `.. admonition::` (and the shorthand `.. note::`, `.. warning::`,
+  `.. important::`).
+- `.. title::` for page titles.
+- `.. importdoc::` + Pandoc-style references for cross-referencing Nim symbols.
+- `.. image::` for images.
+
+## Migration steps
+
+### 1. Admonitions
+
+Replace mdBook's fenced-code admonitions with RST directives:
+
+- ` ```admonish warning` / ` ```admonition warning` → `.. warning::`
+- ` ```admonish note` / ` ```admonition note` → `.. note::`
+- ` ```admonish important` → `.. important::`
+- ` ```admonish info` → `.. note::` (there is **no** `info` directive; map it
+  to `note`)
+
+Valid admonition directives in Nim's RST are: `admonition`, `attention`,
+`caution`, `danger`, `error`, `hint`, `important`, `note`, `tip`, `warning`.
+Map any mdBook admonition type not in this list to the closest valid one
+(e.g. `info` → `note`).
+
+The body text must be indented (3 spaces) under the directive. Remove the
+surrounding ` ``` ` fences.
+
+### 2. Code inclusion
+
+Replace mdBook's `{{#include PATH}}` and `{{#shiftinclude auto:PATH:NAME}}` with
+`.. include::`:
+
+- Whole file: `{{#include PATH}}` or `{{#shiftinclude auto:PATH:all}}` →
+
+  ```
+  .. include:: PATH
+     :code:
+  ```
+
+- Selective (named section): `{{#shiftinclude auto:PATH:NAME}}` →
+
+  ```
+  .. include:: PATH
+     :start-after: #ANCHOR: NAME
+     :end-before: #ANCHOR_END: NAME
+     :code:
+  ```
+
+Notes:
+
+- `:code:` gives Nim syntax highlighting (defaults to Nim; use `:code: <lang>`
+  for other languages).
+- The `#ANCHOR:` / `#ANCHOR_END:` markers must exist in the source `.nim`
+  files. Normalize them to `#ANCHOR:` (no space after `#`) — a space after `#`
+  is interpreted as a Markdown heading.
+- Include paths are resolved **relative to each `.md` file's own directory**
+  (not the book root). Adjust `../` counts accordingly.
+- Remove the surrounding ` ```nim ` fences — `.. include::` is a block
+  directive, not inline.
+
+### 3. Remove mdBook artifacts
+
+Remove any leftover mdBook-specific markup, in particular `<!-- toc -->`
+comments (mdBook's table-of-contents placeholder). `nim book` generates its own
+TOC from the document headings, so these placeholders are dead and should be
+deleted.
+
+### 4. Emphasis syntax
+
+Replace underscore emphasis with asterisks: `_italic_` → `*italic*` (and
+`__bold__` → `**bold**` if present). Nim's Markdown dialect does not support
+`_` for emphasis — only `*`.
+
+Be careful not to touch underscores that are part of identifiers, filenames, or
+URLs (e.g. `http_server_middleware.md`, `YOUR_NTFY_TOPIC_NAME`, `#ANCHOR_END`).
+Only convert genuine emphasis markup.
+
+### 5. Titles
+
+Add `.. title:: <Title>` at the top of each document (before any other
+content), using the document's first heading as the title.
+
+- **Use plain text only.** `.. title::` renders its argument as RST and then
+  HTML-escapes the result, so any markup or escapable characters produce
+  garbage:
+  - Backticks (`` ` ``) → escaped `<tt>` HTML.
+  - `*` and `_` → emphasis markup.
+  - `&`, `<`, `>`, `"` → HTML-escaped to `&amp;`, `&lt;`, `&gt;`, `&quot;`.
+- So strip/replace any of these from the title. For example,
+  `Scaling & Finishing Touches` must become `Scaling and Finishing Touches`
+  (or otherwise remove the `&`), because `&` renders as `&amp;`.
+- Remove the original top-level `# Heading` (it's now redundant with
+  `.. title::`).
+- Promote all remaining headings one level: `##` → `#`, `###` → `##`, etc.
+
+### 6. References
+
+There are **two distinct kinds** of references, with different syntax:
+
+**6a. Module and page links** — use **regular Markdown links** (NOT `importdoc`
+references). Module/page references via `importdoc` resolve inconsistently
+(e.g. `chronos` resolves but `httpagent` doesn't), so always use explicit
+Markdown links:
+
+- Page link: `[Errors and exceptions](./error_handling.html)`
+- Module link: `[httpagent](./api/chronos/apps/http/httpagent.html)`
+
+The `.html` path is relative to the current page's location (adjust `../` as
+needed). API module pages live under `./api/chronos/...`.
+
+**6b. Nim code references** (symbols, procs, types, etc.) — use Pandoc-style
+references, resolved via `.. importdoc::`:
+
+**First read these to learn the syntax:**
+
+- https://nim-lang.org/docs/markdown_rst.html#referencing
+- https://nim-lang.org/docs/docgen.html#simple-documentation-links
+
+- **The reference syntax is `[Ref]`** (square brackets, no trailing
+  underscore). It is **not** `` `ref`_ `` and **not** `ref_`.
+- The API docs live in `./api` (i.e. `<outdir>/api/`), so `importdoc` paths
+  must point there: `.. importdoc:: ../../api/chronos/module` (adjust `../`
+  count for the file's depth).
+- **Unique symbols** → `[symbol]`.
+- **Ambiguous/overloaded symbols** (defined in multiple modules, or multiple
+  overloads) → use the parenthesized signature form:
+  `[symbol(ParamType1, ParamType2)]`. This is the disambiguation syntax (NOT
+  the comma-separated complex name).
+- Leave stdlib links (`nim-lang.org/docs/...`) as-is — they can't be resolved
+  via `importdoc`.
+
+### 7. Images
+
+Replace Markdown image syntax `![alt](path)` with `.. image:: path` (optionally
+with `:alt:`).
+
+## Verification
+
+After migration, build with:
+
+```sh
+nim book --outdir:<outdir> book
+```
+
+and check:
+
+- No broken-link warnings.
+- All `importdoc` references resolve (no "cannot open ...idx" errors).
+- Titles render cleanly (no escaped HTML).
+- Code blocks are syntax-highlighted.
+- The sidebar navigation reflects `SUMMARY.md` (with foldable sections and
+  current-page highlighting).
--- a/doc/nimdoc.css
+++ b/doc/nimdoc.css
@@ -553,6 +553,11 @@ ul.nested-toc-section {
 ul.nested-toc-section > li {
  margin-left: 1.25em; }

+ul.simple-toc-section a.current,
+ul.nested-toc-section a.current {
+  font-weight: bold;
+  color: var(--anchor-focus);
+}

 ol.arabic {
  list-style: decimal; }
@@ -1139,3 +1144,7 @@ span.pragmawrap {
 span.attachedType {
  display: none;
  visibility: hidden; }
+
+summary {
+  cursor: pointer;
+}
--- a/koch.nim
+++ b/koch.nim
@@ -751,6 +751,7 @@ proc runCI(cmd: string) =

    execFold("Run nimdoc tests", "nim r nimdoc/tester")
    execFold("Run rst2html tests", "nim r nimdoc/rsttester")
+    execFold("Run nimbook tests", "nim r nimdoc/booktester")
    execFold("Run nimpretty tests", "nim r nimpretty/tester.nim")
    when defined(posix):
      # refs #18385, build with -d:release instead of -d:danger for testing
--- a/lib/packages/docutils/rst.nim
+++ b/lib/packages/docutils/rst.nim
@@ -3425,8 +3425,13 @@ proc dirIndex(p: var RstParser): PRstNode =
  result = parseDirective(p, rnIndex, {}, parseSectionWrapper)

 proc dirAdmonition(p: var RstParser, d: string): PRstNode =
-  result = parseDirective(p, rnAdmonition, {}, parseSectionWrapper)
+  result = parseDirective(p, rnAdmonition, {hasOptions}, parseSectionWrapper)
  result.adType = d
+  result.title = result.getFieldValue("title").strip()
+  result.collapsible = result.getFieldValue("collapsible") != ""
+  result.closed = result.collapsible and
+    result.getFieldValue("collapsible").strip() == "closed"
+  result.sons[1] = nil

 proc dirDefaultRole(p: var RstParser): PRstNode =
  result = parseDirective(p, rnDefaultRole, {hasArg}, nil)
--- a/lib/packages/docutils/rstast.nim
+++ b/lib/packages/docutils/rstast.nim
@@ -104,6 +104,12 @@ type
    of rnAdmonition:
      adType*: string         ## admonition type: "note", "caution", etc. This
                              ## text will set the style and also be displayed
+      title*: string          ## this text will be displayed (if given)
+                              ## instead of the admonition type
+      collapsible*: bool      ## if set, the admonition is rendered
+                              ## as a collapsible block in HTML
+      closed*: bool           ## if set, and ``collapsible`` is ``true``,
+                              ## render the collapsible block closed by default
    of rnOverline, rnHeadline, rnMarkdownHeadline:
      level*: int             ## level of headings starting from 1 (main
                              ## chapter) to larger ones (minor sub-sections)
--- a/lib/packages/docutils/rstgen.nim
+++ b/lib/packages/docutils/rstgen.nim
@@ -333,7 +333,7 @@ proc setIndexTerm*(d: var RstGenerator; k: IndexEntryKind, htmlFile, id, term: s
  ## The `id` will be appended with a hash character only if its length is not
  ## zero, otherwise no specific anchor will be generated. In general you
  ## should only pass an empty `id` value for the title of standalone rst
-  ## documents (they are special for the `mergeIndexes() <#mergeIndexes,string>`_
+  ## documents (they are special for the `mergeIndexes() <#mergeIndexes,string,bool,bool>`_
  ## proc, see `Index (idx) file format <docgen.html#index-idx-file-format>`_
  ## for more information). Unlike other index terms, title entries are
  ## inserted at the beginning of the accumulated buffer to maintain a logical
@@ -574,10 +574,14 @@ proc generateModuleJumps(modules: seq[string]): string =

  result.add(chunks.join(", ") & ".<br/>")

-proc readIndexDir*(dir: string):
+proc readIndexDir*(dir: string, exclCode = false, inclHeaders = false):
    tuple[modules: seq[string], symbols: seq[IndexEntry], docs: IndexedDocs] =
  ## Walks `dir` reading ``.idx`` files converting them in IndexEntry items.
  ##
+  ## If  `exclCode` is  `true`, skip  `.idx ` files for Nim modules.
+  ##
+  ## If  `inclHeaders` is  `true`, index markup headers.
+  ##
  ## Returns the list of found module names, the list of free symbol entries
  ## and the different documentation indexes. The list of modules is sorted.
  ## See the documentation of ``mergeIndexes`` for details.
@@ -593,6 +597,8 @@ proc readIndexDir*(dir: string):
      # Depending on type add this to the list of symbols or table of APIs.

      if title.kind == ieNimTitle:
+        if exclCode:
+          continue
        for i in 0 ..< fileEntries.len:
          if fileEntries[i].kind != ieNim:
            continue
@@ -613,15 +619,20 @@ proc readIndexDir*(dir: string):
        title.aux = "doc_toc_" & $result.docs.len
        result.docs[title] = fileEntries

+      var indexedRoles = {ieIdxRole}
+
+      if inclHeaders:
+        indexedRoles.incl(ieHeading)
+
      for i in 0 ..< fileEntries.len:
-        if fileEntries[i].kind != ieIdxRole:
+        if fileEntries[i].kind notin indexedRoles:
          continue

        setLen(result.symbols, L + 1)
        result.symbols[L] = fileEntries[i]
        inc L

-proc mergeIndexes*(dir: string): string =
+proc mergeIndexes*(dir: string, exclCode = false, inclHeaders = false): string =
  ## Merges all index files in `dir` and returns the generated index as HTML.
  ##
  ## This proc will first scan `dir` for index files with the ``.idx``
@@ -649,7 +660,7 @@ proc mergeIndexes*(dir: string): string =
  ##
  ## Returns the merged and sorted indices into a single HTML block which can
  ## be further embedded into nimdoc templates.
-  var (modules, symbols, docs) = readIndexDir(dir)
+  var (modules, symbols, docs) = readIndexDir(dir, exclCode, inclHeaders)
  sort(modules, system.cmp)

  result = ""
@@ -1069,15 +1080,25 @@ proc renderAdmonition(d: PDoc, n: PRstNode, result: var string) =
  of "danger", "error":
    htmlCls = "admonition-error"; texSz = "\\Large"; texColor = "red"
  else: discard
-  let txt = n.adType.capitalizeAscii()
+  let txt = if n.title != "": n.title else: n.adType.capitalizeAscii()
  let htmlHead = "<div class=\"admonition " & htmlCls & "\">"
-  renderAux(d, n,
+  let htmlBody =
+    if n.collapsible:
+      if n.closed:
+        htmlHead & "<details><summary><span$2 class=\"" & htmlCls & "-text\"><b>" & txt &
+        "</b></span></summary>\n" & "$1</details></div>\n"
+      else:
+        htmlHead & "<details open><summary><span$2 class=\"" & htmlCls & "-text\"><b>" & txt &
+        "</b></span></summary>\n" & "$1</details></div>\n"
+    else:
      htmlHead & "<span$2 class=\"" & htmlCls & "-text\"><b>" & txt &
-        ":</b></span>\n" & "$1</div>\n",
-      "\n\n\\begin{rstadmonition}[borderline west={0.2em}{0pt}{" &
-        texColor & "}]$2\n" &
-        "{" & texSz & "\\color{" & texColor & "}{\\textbf{" & txt & ":}}} " &
-        "$1\n\\end{rstadmonition}\n",
+      ":</b></span>\n" & "$1</div>\n"
+  let texBody = "\n\n\\begin{rstadmonition}[borderline west={0.2em}{0pt}{" &
+    texColor & "}]$2\n" &
+    "{" & texSz & "\\color{" & texColor & "}{\\textbf{" & txt & ":}}} " &
+    "$1\n\\end{rstadmonition}\n"
+  renderAux(d, n,
+      htmlBody, texBody,
      result)

 proc renderHyperlink(d: PDoc, text, link: PRstNode, result: var string,
--- a/lib/packages/docutils/rstidx.nim
+++ b/lib/packages/docutils/rstidx.nim
@@ -35,7 +35,7 @@ proc isDocumentationTitle*(hyperlink: string): bool =
  ## Returns true if the hyperlink is actually a documentation title.
  ##
  ## Documentation titles lack the hash. See `mergeIndexes()
-  ## <#mergeIndexes,string>`_ for a more detailed explanation.
+  ## <#mergeIndexes,string,bool,bool>`_ for a more detailed explanation.
  result = hyperlink.find('#') < 0

 proc `$`*(e: IndexEntry): string =
--- a/nimdoc/bookproject/SUMMARY.md
+++ b/nimdoc/bookproject/SUMMARY.md
@@ -0,0 +1,18 @@
+- [Intro](./intro.md)
+- [Page 1](./page1.md)
+
+# Section 1
+
+- [Intro](./sections/1/intro.md)
+- [Page 2](./sections/1/page2.md)
+  - [Subpage 1](./sections/1/page2/subpage1.md)
+
+- Section 2
+  - [Intro](./sections/2/intro.md)
+  - [Page 3](./sections/2/page3.md)
+    - [Subpage 2](./sections/2/page3/subpage2.md)
+
+- [API docs](./api/theindex.html)
+- [nim-lang.org](https://nim-lang.org)
+- [Four-oh-four](./nosuchpage.md)
+
--- a/nimdoc/bookproject/code1.nim
+++ b/nimdoc/bookproject/code1.nim
@@ -0,0 +1,2 @@
+proc double*(x: int): int =
+  x * 2
--- a/nimdoc/bookproject/code2.nim
+++ b/nimdoc/bookproject/code2.nim
@@ -0,0 +1,10 @@
+proc single*(x: int): int =
+  x * 1
+
+#doublestart
+proc double*(x: int): int =
+  x * 2
+#doubleend
+
+proc triple*(x: int): int =
+  x * 3
--- a/nimdoc/bookproject/code3.py
+++ b/nimdoc/bookproject/code3.py
@@ -0,0 +1,3 @@
+# This is Python
+def double(x: int) -> int:
+    return x * 2
--- a/nimdoc/bookproject/expected/api/code1.html
+++ b/nimdoc/bookproject/expected/api/code1.html
@@ -0,0 +1,114 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+<!--  This file is generated by Nim. -->
+<html xmlns="https://www.w3.org/1999/xhtml" xml:lang="en" lang="en" data-theme="auto">
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
+<meta name="viewport" content="width=device-width, initial-scale=1.0">
+<title>nimdoc/bookproject/code1</title>
+
+<!-- Google fonts -->
+<link href='https://fonts.googleapis.com/css?family=Lato:400,600,900' rel='stylesheet' type='text/css'/>
+<link href='https://fonts.googleapis.com/css?family=Source+Code+Pro:400,500,600' rel='stylesheet' type='text/css'/>
+
+<!-- Favicon -->
+<link rel="shortcut icon" href="data:image/x-icon;base64,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"/>
+<link rel="icon" type="image/png" sizes="32x32" href="data:image/png;base64,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">
+
+<!-- CSS -->
+<link rel="stylesheet" type="text/css" href="nimdoc.out.css">
+
+<!-- JS -->
+<script type="text/javascript" src="dochack.js"></script>
+</head>
+<body>
+  <div class="document" id="documentId">
+    <input type="checkbox" id="nav-toggle" hidden>
+    <label for="nav-toggle" id="nav-burger">&#9776;</label>
+    <label for="nav-toggle" id="nav-overlay"></label>
+    <div class="container">
+      <h1 class="title">nimdoc/bookproject/code1</h1>
+      <div class="row">
+  <div class="three columns">
+    <div class="theme-select-wrapper">
+  <label for="theme-select">Theme:&nbsp;</label>
+  <select id="theme-select" onchange="setTheme(this.value)">
+    <option value="auto">🌗 Match OS</option>
+    <option value="dark">🌑 Dark</option>
+    <option value="light">🌕 Light</option>
+  </select>
+</div>
+
+    <div id="global-links">
+  
+  <ul class="simple">
+  <li><a id="indexLink" href="theindex.html">Index</a></li>
+</ul>
+
+</div>
+
+      <div id="searchInputDiv">
+  Search: <input type="search" id="searchInput" oninput="search()"/>
+</div>
+
+    <div class="search-groupby">
+  Group by:
+  <select onchange="groupBy(this.value)">
+    <option value="section">Section</option>
+    <option value="type">Type</option>
+  </select>
+</div>
+
+    <ul class="simple simple-toc" id="toc-list">
+  <li>
+  <details open>
+    <summary><a class="reference reference-toplevel" href="#12" id="62">Procs</a></summary>
+    <ul class="simple simple-toc-section">
+      <ul class="simple nested-toc-section">double
+  <li><a class="reference" href="#double%2Cint" title="double(x: int): int">double(x: int): int</a></li>
+
+</ul>
+
+    </ul>
+  </details>
+</li>
+
+</ul>
+
+  </div>
+  <div class="nine columns" id="content">
+    
+    <div id="tocRoot"></div>
+    
+    <p class="module-desc"></p>
+    <div class="section" id="12">
+  <h1><a class="toc-backref" href="#12">Procs</a></h1>
+  <dl class="item">
+    <div id="double-procs-all">
+  <div id="double,int">
+  <dt><pre><span class="Keyword">proc</span> <a href="#double%2Cint"><span class="Identifier">double</span></a><span class="Other">(</span><span class="Identifier">x</span><span class="Other">:</span> <span class="Identifier">int</span><span class="Other">)</span><span class="Other">:</span> <span class="Identifier">int</span> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
+  <dd>
+    
+    
+    
+  </dd>
+</div>
+
+</div>
+
+  </dl>
+</div>
+
+  </div>
+</div>
+
+      <div class="twelve-columns footer">
+        <span class="nim-sprite"></span>
+        <br>
+        <small style="color: var(--hint);">Made with Nim. Generated: 1970-01-02 03:46:40 UTC</small>
+      </div>
+    </div>
+  </div>
+  
+</body>
+</html>
--- a/nimdoc/bookproject/expected/api/code1.idx
+++ b/nimdoc/bookproject/expected/api/code1.idx
@@ -0,0 +1,2 @@
+nimTitle	code1	code1.html	module nimdoc/bookproject/code1		0
+nim	double	code1.html#double,int	proc double(x: int): int		1
--- a/nimdoc/bookproject/expected/api/theindex.html
+++ b/nimdoc/bookproject/expected/api/theindex.html
@@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+<!--  This file is generated by Nim. -->
+<html xmlns="https://www.w3.org/1999/xhtml" xml:lang="en" lang="en" data-theme="auto">
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
+<meta name="viewport" content="width=device-width, initial-scale=1.0">
+<title>Index</title>
+
+<!-- Google fonts -->
+<link href='https://fonts.googleapis.com/css?family=Lato:400,600,900' rel='stylesheet' type='text/css'/>
+<link href='https://fonts.googleapis.com/css?family=Source+Code+Pro:400,500,600' rel='stylesheet' type='text/css'/>
+
+<!-- Favicon -->
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+<link rel="icon" type="image/png" sizes="32x32" href="data:image/png;base64,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">
+
+<!-- CSS -->
+<link rel="stylesheet" type="text/css" href="nimdoc.out.css">
+
+<!-- JS -->
+<script type="text/javascript" src="dochack.js"></script>
+</head>
+<body>
+  <div class="document" id="documentId">
+    <input type="checkbox" id="nav-toggle" hidden>
+    <label for="nav-toggle" id="nav-burger">&#9776;</label>
+    <label for="nav-toggle" id="nav-overlay"></label>
+    <div class="container">
+      <h1 class="title">Index</h1>
+      Modules: <a href="code1.html">code1</a>.<br/><p /><h2>API symbols</h2>
+<dl><dt><a name="double" href="#double"><span>double:</span></a></dt><dd><ul class="simple">
+<li><a class="reference external"
+          data-doc-search-tag="code1: proc double(x: int): int" href="code1.html#double%2Cint">code1: proc double(x: int): int</a></li>
+          </ul></dd>
+</dl>
+      <div class="twelve-columns footer">
+        <span class="nim-sprite"></span>
+        <br>
+        <small style="color: var(--hint);">Made with Nim. Generated: 1970-01-02 03:46:40 UTC</small>
+      </div>
+    </div>
+  </div>
+  
+</body>
+</html>
--- a/nimdoc/bookproject/expected/intro.html
+++ b/nimdoc/bookproject/expected/intro.html
@@ -0,0 +1,127 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+<!--  This file is generated by Nim. -->
+<html xmlns="https://www.w3.org/1999/xhtml" xml:lang="en" lang="en" data-theme="auto">
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
+<meta name="viewport" content="width=device-width, initial-scale=1.0">
+<title>Welcome to Nim Book</title>
+
+<!-- Google fonts -->
+<link href='https://fonts.googleapis.com/css?family=Lato:400,600,900' rel='stylesheet' type='text/css'/>
+<link href='https://fonts.googleapis.com/css?family=Source+Code+Pro:400,500,600' rel='stylesheet' type='text/css'/>
+
+<!-- Favicon -->
+<link rel="shortcut icon" href="data:image/x-icon;base64,AAABAAEAEBAAAAEAIABoBAAAFgAAACgAAAAQAAAAIAAAAAEAIAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AAAAAAUAAAAF////AP///wD///8A////AP///wD///8A////AP///wD///8A////AAAAAAIAAABbAAAAlQAAAKIAAACbAAAAmwAAAKIAAACVAAAAWwAAAAL///8A////AP///wD///8A////AAAAABQAAADAAAAAYwAAAA3///8A////AP///wD///8AAAAADQAAAGMAAADAAAAAFP///wD///8A////AP///wAAAACdAAAAOv///wD///8A////AP///wD///8A////AP///wD///8AAAAAOgAAAJ3///8A////AP///wAAAAAnAAAAcP///wAAAAAoAAAASv///wD///8A////AP///wAAAABKAAAAKP///wAAAABwAAAAJ////wD///8AAAAAgQAAABwAAACIAAAAkAAAAJMAAACtAAAAFQAAABUAAACtAAAAkwAAAJAAAACIAAAAHAAAAIH///8A////AAAAAKQAAACrAAAAaP///wD///8AAAAARQAAANIAAADSAAAARf///wD///8AAAAAaAAAAKsAAACk////AAAAADMAAACcAAAAnQAAABj///8A////AP///wAAAAAYAAAAGP///wD///8A////AAAAABgAAACdAAAAnAAAADMAAAB1AAAAwwAAAP8AAADpAAAAsQAAAE4AAAAb////AP///wAAAAAbAAAATgAAALEAAADpAAAA/wAAAMMAAAB1AAAAtwAAAOkAAAD/AAAA/wAAAP8AAADvAAAA3gAAAN4AAADeAAAA3gAAAO8AAAD/AAAA/wAAAP8AAADpAAAAtwAAAGUAAAA/AAAA3wAAAP8AAAD/AAAA/wAAAP8AAAD/AAAA/wAAAP8AAAD/AAAA/wAAAP8AAADfAAAAPwAAAGX///8A////AAAAAEgAAADtAAAAvwAAAL0AAADGAAAA7wAAAO8AAADGAAAAvQAAAL8AAADtAAAASP///wD///8A////AP///wD///8AAAAAO////wD///8A////AAAAAIcAAACH////AP///wD///8AAAAAO////wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A////AP///wD///8A//8AAP//AAD4HwAA7/cAAN/7AAD//wAAoYUAAJ55AACf+QAAh+EAAAAAAADAAwAA4AcAAP5/AAD//wAA//8AAA=="/>
+<link rel="icon" type="image/png" sizes="32x32" href="data:image/png;base64,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">
+
+<!-- CSS -->
+<link rel="stylesheet" type="text/css" href="nimdoc.out.css">
+
+<!-- JS -->
+<script type="text/javascript" src="dochack.js"></script>
+</head>
+<body>
+  <div class="document" id="documentId">
+    <input type="checkbox" id="nav-toggle" hidden>
+    <label for="nav-toggle" id="nav-burger">&#9776;</label>
+    <label for="nav-toggle" id="nav-overlay"></label>
+    <div class="container">
+      <h1 class="title">Welcome to Nim Book</h1>
+      <div class="row">
+  <div class="three columns">
+    <div class="theme-select-wrapper">
+  <label for="theme-select">Theme:&nbsp;</label>
+  <select id="theme-select" onchange="setTheme(this.value)">
+    <option value="auto">🌗 Match OS</option>
+    <option value="dark">🌑 Dark</option>
+    <option value="light">🌕 Light</option>
+  </select>
+</div>
+
+    <div id="global-links">
+  <ul class="simple simple-toc-section"><li><a href="intro.html" class="current">Intro</a></li><li><a href="page1.html" class="">Page 1</a></li><li><strong>Section 1</strong></li><li><a href="sections/1/intro.html" class="">Intro</a></li><li><details><summary><a href="sections/1/page2.html" class="">Page 2</a></summary><ul class="simple nested-toc-section"><li><a href="sections/1/page2/subpage1.html" class="">Subpage 1</a></li></ul></details></li><li><details><summary>Section 2</summary><ul class="simple nested-toc-section"><li><a href="sections/2/intro.html" class="">Intro</a></li><li><details><summary><a href="sections/2/page3.html" class="">Page 3</a></summary><ul class="simple nested-toc-section"><li><a href="sections/2/page3/subpage2.html" class="">Subpage 2</a></li></ul></details></li></ul></details></li><li><a href="./api/theindex.html" class="">API docs</a></li><li><a href="https://nim-lang.org" class="">nim-lang.org</a></li><li><a href="./nosuchpage.md" class="">Four-oh-four</a></li></ul>
+  <ul class="simple">
+  <li><a id="indexLink" href="theindex.html">Index</a></li>
+</ul>
+
+</div>
+
+      <div id="searchInputDiv">
+  Search: <input type="search" id="searchInput" oninput="search()"/>
+</div>
+
+    
+    <ul class="simple simple-toc" id="toc-list">
+  <li><a class="reference" id="code_toc" href="#code">Code</a></li>
+<li><a class="reference" id="admonitions_toc" href="#admonitions">Admonitions</a></li>
+<li><a class="reference" id="links_toc" href="#links">Links</a></li>
+
+</ul>
+
+  </div>
+  <div class="nine columns" id="content">
+    
+    <div id="tocRoot"></div>
+    
+    <p class="module-desc"><p>This is a test project for <tt class="docutils literal"><span class="pre"><span class="program">nim</span> <span class="option">book</span></span></tt>.</p>
+
+<h1><a class="toc-backref" id="code" href="#code">Code</a></h1><p>Inline code snippet:</p>
+<p><pre class="listing"><span class="Keyword">proc</span> <span class="Identifier">twice</span><span class="Operator">*</span><span class="Punctuation">(</span><span class="Identifier">a</span><span class="Punctuation">:</span> <span class="Identifier">int</span><span class="Punctuation">)</span><span class="Punctuation">:</span> <span class="Identifier">int</span> <span class="Operator">=</span>
+  <span class="Identifier">a</span> <span class="Operator">*</span> <span class="DecNumber">2</span></pre></p>
+<p>This snippet is tested during documentation build:</p>
+<p><pre class="listing"><span class="Keyword">proc</span> <span class="Identifier">twice</span><span class="Operator">*</span><span class="Punctuation">(</span><span class="Identifier">a</span><span class="Punctuation">:</span> <span class="Identifier">int</span><span class="Punctuation">)</span><span class="Punctuation">:</span> <span class="Identifier">int</span> <span class="Operator">=</span>
+  <span class="Identifier">a</span> <span class="Operator">*</span> <span class="DecNumber">2</span>
+
+<span class="Identifier">assert</span> <span class="FloatNumber">10.</span><span class="Identifier">twice</span> <span class="Operator">==</span> <span class="DecNumber">20</span></pre></p>
+<p>The same but using <tt class="docutils literal"><span class="pre">.. code::</span></tt> directive:</p>
+<pre class="listing">proc twice*(a: int): int =
+  a * 2</pre><pre class="listing">proc twice*(a: int): int =
+  a * 2
+
+assert 10.twice == 20</pre><p>Code included from a source file:</p>
+<pre class="listing"><span class="Keyword">proc</span> <span class="Identifier">double</span><span class="Operator">*</span><span class="Punctuation">(</span><span class="Identifier">x</span><span class="Punctuation">:</span> <span class="Identifier">int</span><span class="Punctuation">)</span><span class="Punctuation">:</span> <span class="Identifier">int</span> <span class="Operator">=</span>
+  <span class="Identifier">x</span> <span class="Operator">*</span> <span class="DecNumber">2</span>
+</pre><p>Selective inclusuion:</p>
+<pre class="listing">
+<span class="Keyword">proc</span> <span class="Identifier">double</span><span class="Operator">*</span><span class="Punctuation">(</span><span class="Identifier">x</span><span class="Punctuation">:</span> <span class="Identifier">int</span><span class="Punctuation">)</span><span class="Punctuation">:</span> <span class="Identifier">int</span> <span class="Operator">=</span>
+  <span class="Identifier">x</span> <span class="Operator">*</span> <span class="DecNumber">2</span>
+</pre><p>Doesn't have to be Nim code:</p>
+<pre class="listing"><span class="Comment"># This is Python</span>
+<span class="Keyword">def</span> <span class="Identifier">double</span><span class="Punctuation">(</span><span class="Identifier">x</span><span class="Punctuation">:</span> <span class="Identifier">int</span><span class="Punctuation">)</span> <span class="Operator">-&gt;</span> <span class="Identifier">int</span><span class="Punctuation">:</span>
+    <span class="Keyword">return</span> <span class="Identifier">x</span> <span class="Operator">*</span> <span class="DecNumber">2</span>
+</pre>
+<h1><a class="toc-backref" id="admonitions" href="#admonitions">Admonitions</a></h1><div class="admonition admonition-info"><span class="admonition-info-text"><b>Note:</b></span>
+General info</div>
+<div class="admonition admonition-warning"><span class="admonition-warning-text"><b>Warning:</b></span>
+<p>It's dangerous to go alone!</p>
+<p>Take this!</p>
+</div>
+<div class="admonition admonition-error"><span class="admonition-error-text"><b>Error:</b></span>
+Oh, snap :-(</div>
+<div class="admonition admonition-warning"><span class="admonition-warning-text"><b>Important:</b></span>
+Admonitions can contain lists and code blocks.<ul class="simple"><li>This</li>
+<li>is</li>
+<li>great!</li>
+</ul>
+<pre class="listing"><span class="Identifier">echo</span> <span class="StringLit">&quot;Indeed&quot;</span></pre></div>
+
+<h1><a class="toc-backref" id="links" href="#links">Links</a></h1><p>This is a link to a heading on the same page: <a class="reference internal" href="#code">Code</a>.</p>
+<p>This is a link to a heading on another page: <a class="reference external" href="sections/1/intro.html#heading">intro.md: Heading</a>.</p>
+<p>Same, but with different syntax: <a class="reference external" href="sections/1/intro.html#heading">intro.md: Heading</a>.</p>
+<p>You can use standard Markdown syntax, too: <a class="reference external" href="page1.html#heading">I am a link</a> </p>
+</p>
+    
+  </div>
+</div>
+
+      <div class="twelve-columns footer">
+        <span class="nim-sprite"></span>
+        <br>
+        <small style="color: var(--hint);">Made with Nim. Generated: 1970-01-02 03:46:40 UTC</small>
+      </div>
+    </div>
+  </div>
+  
+</body>
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--- a/nimdoc/bookproject/expected/intro.idx
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+
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+    <input type="checkbox" id="nav-toggle" hidden>
+    <label for="nav-toggle" id="nav-burger">&#9776;</label>
+    <label for="nav-toggle" id="nav-overlay"></label>
+    <div class="container">
+      <h1 class="title">Another page</h1>
+      <div class="row">
+  <div class="three columns">
+    <div class="theme-select-wrapper">
+  <label for="theme-select">Theme:&nbsp;</label>
+  <select id="theme-select" onchange="setTheme(this.value)">
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+    <option value="light">🌕 Light</option>
+  </select>
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+
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+  <ul class="simple simple-toc-section"><li><a href="intro.html" class="">Intro</a></li><li><a href="page1.html" class="current">Page 1</a></li><li><strong>Section 1</strong></li><li><a href="sections/1/intro.html" class="">Intro</a></li><li><details><summary><a href="sections/1/page2.html" class="">Page 2</a></summary><ul class="simple nested-toc-section"><li><a href="sections/1/page2/subpage1.html" class="">Subpage 1</a></li></ul></details></li><li><details><summary>Section 2</summary><ul class="simple nested-toc-section"><li><a href="sections/2/intro.html" class="">Intro</a></li><li><details><summary><a href="sections/2/page3.html" class="">Page 3</a></summary><ul class="simple nested-toc-section"><li><a href="sections/2/page3/subpage2.html" class="">Subpage 2</a></li></ul></details></li></ul></details></li><li><a href="./api/theindex.html" class="">API docs</a></li><li><a href="https://nim-lang.org" class="">nim-lang.org</a></li><li><a href="./nosuchpage.md" class="">Four-oh-four</a></li></ul>
+  <ul class="simple">
+  <li><a id="indexLink" href="theindex.html">Index</a></li>
+</ul>
+
+</div>
+
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+  Search: <input type="search" id="searchInput" oninput="search()"/>
+</div>
+
+    
+    <ul class="simple simple-toc" id="toc-list">
+  <li><a class="reference" id="section-1_toc" href="#section-1">Section 1</a></li>
+
+</ul>
+
+  </div>
+  <div class="nine columns" id="content">
+    
+    <div id="tocRoot"></div>
+    
+    <p class="module-desc">
+<h1><a class="toc-backref" id="section-1" href="#section-1">Section 1</a></h1><p>Paragraph. </p>
+</p>
+    
+  </div>
+</div>
+
+      <div class="twelve-columns footer">
+        <span class="nim-sprite"></span>
+        <br>
+        <small style="color: var(--hint);">Made with Nim. Generated: 1970-01-02 03:46:40 UTC</small>
+      </div>
+    </div>
+  </div>
+  
+</body>
+</html>
--- a/nimdoc/bookproject/expected/page1.idx
+++ b/nimdoc/bookproject/expected/page1.idx
@@ -0,0 +1,2 @@
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+<meta name="viewport" content="width=device-width, initial-scale=1.0">
+<title>Welcome to Section 1</title>
+
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+
+<!-- CSS -->
+<link rel="stylesheet" type="text/css" href="../../nimdoc.out.css">
+
+<!-- JS -->
+<script type="text/javascript" src="../../dochack.js"></script>
+</head>
+<body>
+  <div class="document" id="documentId">
+    <input type="checkbox" id="nav-toggle" hidden>
+    <label for="nav-toggle" id="nav-burger">&#9776;</label>
+    <label for="nav-toggle" id="nav-overlay"></label>
+    <div class="container">
+      <h1 class="title">Welcome to Section 1</h1>
+      <div class="row">
+  <div class="three columns">
+    <div class="theme-select-wrapper">
+  <label for="theme-select">Theme:&nbsp;</label>
+  <select id="theme-select" onchange="setTheme(this.value)">
+    <option value="auto">🌗 Match OS</option>
+    <option value="dark">🌑 Dark</option>
+    <option value="light">🌕 Light</option>
+  </select>
+</div>
+
+    <div id="global-links">
+  <ul class="simple simple-toc-section"><li><a href="../../intro.html" class="">Intro</a></li><li><a href="../../page1.html" class="">Page 1</a></li><li><strong>Section 1</strong></li><li><a href="intro.html" class="current">Intro</a></li><li><details><summary><a href="page2.html" class="">Page 2</a></summary><ul class="simple nested-toc-section"><li><a href="page2/subpage1.html" class="">Subpage 1</a></li></ul></details></li><li><details><summary>Section 2</summary><ul class="simple nested-toc-section"><li><a href="../2/intro.html" class="">Intro</a></li><li><details><summary><a href="../2/page3.html" class="">Page 3</a></summary><ul class="simple nested-toc-section"><li><a href="../2/page3/subpage2.html" class="">Subpage 2</a></li></ul></details></li></ul></details></li><li><a href="./api/theindex.html" class="">API docs</a></li><li><a href="https://nim-lang.org" class="">nim-lang.org</a></li><li><a href="./nosuchpage.md" class="">Four-oh-four</a></li></ul>
+  <ul class="simple">
+  <li><a id="indexLink" href="../../theindex.html">Index</a></li>
+</ul>
+
+</div>
+
+      <div id="searchInputDiv">
+  Search: <input type="search" id="searchInput" oninput="search()"/>
+</div>
+
+    
+    <ul class="simple simple-toc" id="toc-list">
+  <li><a class="reference" id="heading_toc" href="#heading">Heading</a></li>
+
+</ul>
+
+  </div>
+  <div class="nine columns" id="content">
+    
+    <div id="tocRoot"></div>
+    
+    <p class="module-desc">
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+    
+  </div>
+</div>
+
+      <div class="twelve-columns footer">
+        <span class="nim-sprite"></span>
+        <br>
+        <small style="color: var(--hint);">Made with Nim. Generated: 1970-01-02 03:46:40 UTC</small>
+      </div>
+    </div>
+  </div>
+  
+</body>
+</html>
--- a/nimdoc/bookproject/expected/sections/1/intro.idx
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+
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+  <ul class="simple simple-toc-section"><li><a href="../../intro.html" class="">Intro</a></li><li><a href="../../page1.html" class="">Page 1</a></li><li><strong>Section 1</strong></li><li><a href="intro.html" class="">Intro</a></li><li><details open><summary><a href="page2.html" class="current">Page 2</a></summary><ul class="simple nested-toc-section"><li><a href="page2/subpage1.html" class="">Subpage 1</a></li></ul></details></li><li><details><summary>Section 2</summary><ul class="simple nested-toc-section"><li><a href="../2/intro.html" class="">Intro</a></li><li><details><summary><a href="../2/page3.html" class="">Page 3</a></summary><ul class="simple nested-toc-section"><li><a href="../2/page3/subpage2.html" class="">Subpage 2</a></li></ul></details></li></ul></details></li><li><a href="./api/theindex.html" class="">API docs</a></li><li><a href="https://nim-lang.org" class="">nim-lang.org</a></li><li><a href="./nosuchpage.md" class="">Four-oh-four</a></li></ul>
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+
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+
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+  <div class="nine columns" id="content">
+    
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+    
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+        <small style="color: var(--hint);">Made with Nim. Generated: 1970-01-02 03:46:40 UTC</small>
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+</html>
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+  <label for="theme-select">Theme:&nbsp;</label>
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+  <ul class="simple simple-toc-section"><li><a href="../../../intro.html" class="">Intro</a></li><li><a href="../../../page1.html" class="">Page 1</a></li><li><strong>Section 1</strong></li><li><a href="../intro.html" class="">Intro</a></li><li><details open><summary><a href="../page2.html" class="">Page 2</a></summary><ul class="simple nested-toc-section"><li><a href="subpage1.html" class="current">Subpage 1</a></li></ul></details></li><li><details><summary>Section 2</summary><ul class="simple nested-toc-section"><li><a href="../../2/intro.html" class="">Intro</a></li><li><details><summary><a href="../../2/page3.html" class="">Page 3</a></summary><ul class="simple nested-toc-section"><li><a href="../../2/page3/subpage2.html" class="">Subpage 2</a></li></ul></details></li></ul></details></li><li><a href="./api/theindex.html" class="">API docs</a></li><li><a href="https://nim-lang.org" class="">nim-lang.org</a></li><li><a href="./nosuchpage.md" class="">Four-oh-four</a></li></ul>
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+
+</ul>
+
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+  <div class="nine columns" id="content">
+    
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+    
+    <p class="module-desc">
+<h1><a class="toc-backref" id="subpage-1" href="#subpage-1">Subpage 1</a></h1></p>
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+        <span class="nim-sprite"></span>
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+  
+</body>
+</html>
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+<title>nimdoc/bookproject/sections/2/intro</title>
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+
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+    <div class="container">
+      <h1 class="title">nimdoc/bookproject/sections/2/intro</h1>
+      <div class="row">
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+    <div class="theme-select-wrapper">
+  <label for="theme-select">Theme:&nbsp;</label>
+  <select id="theme-select" onchange="setTheme(this.value)">
+    <option value="auto">🌗 Match OS</option>
+    <option value="dark">🌑 Dark</option>
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+</div>
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+    <div id="global-links">
+  <ul class="simple simple-toc-section"><li><a href="../../intro.html" class="">Intro</a></li><li><a href="../../page1.html" class="">Page 1</a></li><li><strong>Section 1</strong></li><li><a href="../1/intro.html" class="">Intro</a></li><li><details><summary><a href="../1/page2.html" class="">Page 2</a></summary><ul class="simple nested-toc-section"><li><a href="../1/page2/subpage1.html" class="">Subpage 1</a></li></ul></details></li><li><details open><summary>Section 2</summary><ul class="simple nested-toc-section"><li><a href="intro.html" class="current">Intro</a></li><li><details><summary><a href="page3.html" class="">Page 3</a></summary><ul class="simple nested-toc-section"><li><a href="page3/subpage2.html" class="">Subpage 2</a></li></ul></details></li></ul></details></li><li><a href="./api/theindex.html" class="">API docs</a></li><li><a href="https://nim-lang.org" class="">nim-lang.org</a></li><li><a href="./nosuchpage.md" class="">Four-oh-four</a></li></ul>
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+
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+  Search: <input type="search" id="searchInput" oninput="search()"/>
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+
+    
+    <ul class="simple simple-toc" id="toc-list">
+  <li><a class="reference" id="section-2colon-intro_toc" href="#section-2colon-intro">Section 2: Intro</a></li>
+
+</ul>
+
+  </div>
+  <div class="nine columns" id="content">
+    
+    <div id="tocRoot"></div>
+    
+    <p class="module-desc">
+<h1><a class="toc-backref" id="section-2colon-intro" href="#section-2colon-intro">Section 2: Intro</a></h1></p>
+    
+  </div>
+</div>
+
+      <div class="twelve-columns footer">
+        <span class="nim-sprite"></span>
+        <br>
+        <small style="color: var(--hint);">Made with Nim. Generated: 1970-01-02 03:46:40 UTC</small>
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+  
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+<link href='https://fonts.googleapis.com/css?family=Source+Code+Pro:400,500,600' rel='stylesheet' type='text/css'/>
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+<dt><a name="Heading" href="#Heading"><span>Heading:</span></a></dt><dd><ul class="simple">
+<li><a class="reference external"
+          data-doc-search-tag="Welcome to Section 1:  Heading" href="sections/1/intro.html#heading">Welcome to Section 1:  Heading</a></li>
+          </ul></dd>
+<dt><a name="Links" href="#Links"><span>Links:</span></a></dt><dd><ul class="simple">
+<li><a class="reference external"
+          data-doc-search-tag="Welcome to Nim Book:  Links" href="intro.html#links">Welcome to Nim Book:  Links</a></li>
+          </ul></dd>
+<dt><a name="Page%202" href="#Page%202"><span>Page 2:</span></a></dt><dd><ul class="simple">
+<li><a class="reference external"
+          data-doc-search-tag="page2.md:  Page 2" href="sections/1/page2.html#page-2">page2.md:  Page 2</a></li>
+          </ul></dd>
+<dt><a name="Page%203" href="#Page%203"><span>Page 3:</span></a></dt><dd><ul class="simple">
+<li><a class="reference external"
+          data-doc-search-tag="page3.md:  Page 3" href="sections/2/page3.html#page-3">page3.md:  Page 3</a></li>
+          </ul></dd>
+<dt><a name="Section%201" href="#Section%201"><span>Section 1:</span></a></dt><dd><ul class="simple">
+<li><a class="reference external"
+          data-doc-search-tag="Another page:  Section 1" href="page1.html#section-1">Another page:  Section 1</a></li>
+          </ul></dd>
+<dt><a name="Section%202%3A%20Intro" href="#Section%202%3A%20Intro"><span>Section 2: Intro:</span></a></dt><dd><ul class="simple">
+<li><a class="reference external"
+          data-doc-search-tag="intro.md:  Section 2: Intro" href="sections/2/intro.html#section-2colon-intro">intro.md:  Section 2: Intro</a></li>
+          </ul></dd>
+<dt><a name="Subpage%201" href="#Subpage%201"><span>Subpage 1:</span></a></dt><dd><ul class="simple">
+<li><a class="reference external"
+          data-doc-search-tag="subpage1.md:  Subpage 1" href="sections/1/page2/subpage1.html#subpage-1">subpage1.md:  Subpage 1</a></li>
+          </ul></dd>
+<dt><a name="Subpage%202" href="#Subpage%202"><span>Subpage 2:</span></a></dt><dd><ul class="simple">
+<li><a class="reference external"
+          data-doc-search-tag="subpage2.md:  Subpage 2" href="sections/2/page3/subpage2.html#subpage-2">subpage2.md:  Subpage 2</a></li>
+          </ul></dd>
+</dl>
+      <div class="twelve-columns footer">
+        <span class="nim-sprite"></span>
+        <br>
+        <small style="color: var(--hint);">Made with Nim. Generated: 1970-01-02 03:46:40 UTC</small>
+      </div>
+    </div>
+  </div>
+  
+</body>
+</html>
--- a/nimdoc/bookproject/intro.md
+++ b/nimdoc/bookproject/intro.md
@@ -0,0 +1,85 @@
+.. title:: Welcome to Nim Book
+.. importdoc:: page1
+.. importdoc:: sections/1/intro
+
+This is a test project for `nim book`:cmd:.
+
+# Code
+
+Inline code snippet:
+
+```nim
+proc twice*(a: int): int =
+  a * 2
+```
+
+This snippet is tested during documentation build:
+
+```nim test
+proc twice*(a: int): int =
+  a * 2
+
+assert 10.twice == 20
+```
+
+The same but using `.. code::` directive:
+
+.. code::
+  proc twice*(a: int): int =
+    a * 2
+
+.. code::
+  :test:
+
+  proc twice*(a: int): int =
+    a * 2
+
+  assert 10.twice == 20
+
+Code included from a source file:
+
+.. include:: ./code1.nim
+  :code:
+  
+Selective inclusuion:
+
+.. include:: ./code2.nim
+  :code:
+  :start-after:#doublestart
+  :end-before:#doubleend
+
+Doesn't have to be Nim code:
+
+.. include:: ./code3.py
+  :code: python
+
+# Admonitions
+
+.. note:: General info
+
+.. warning::
+    It's dangerous to go alone!
+
+    Take this!
+
+.. error:: Oh, snap :-(
+
+.. important::
+  Admonitions can contain lists and code blocks.
+
+  - This
+  - is
+  - great!
+
+  .. code-block::
+    echo "Indeed"
+
+# Links
+
+This is a link to a heading on the same page: [Code].
+
+This is a link to a heading on another page: [Heading].
+
+Same, but with different syntax: `Heading`_.
+
+You can use standard Markdown syntax, too: [I am a link](page1.html#heading)
--- a/nimdoc/bookproject/page1.md
+++ b/nimdoc/bookproject/page1.md
@@ -0,0 +1,5 @@
+.. title:: Another page
+
+# Section 1
+
+Paragraph.
--- a/nimdoc/bookproject/sections/1/intro.md
+++ b/nimdoc/bookproject/sections/1/intro.md
@@ -0,0 +1,5 @@
+.. title:: Welcome to Section 1
+
+# Heading
+
+Paragraph.
--- a/nimdoc/bookproject/sections/1/page2.md
+++ b/nimdoc/bookproject/sections/1/page2.md
@@ -0,0 +1 @@
+# Page 2
--- a/nimdoc/bookproject/sections/1/page2/subpage1.md
+++ b/nimdoc/bookproject/sections/1/page2/subpage1.md
@@ -0,0 +1 @@
+# Subpage 1
--- a/nimdoc/bookproject/sections/2/intro.md
+++ b/nimdoc/bookproject/sections/2/intro.md
@@ -0,0 +1 @@
+# Section 2: Intro
--- a/nimdoc/bookproject/sections/2/page3.md
+++ b/nimdoc/bookproject/sections/2/page3.md
@@ -0,0 +1 @@
+# Page 3
--- a/nimdoc/bookproject/sections/2/page3/subpage2.md
+++ b/nimdoc/bookproject/sections/2/page3/subpage2.md
@@ -0,0 +1 @@
+# Subpage 2
--- a/nimdoc/booktester.nim
+++ b/nimdoc/booktester.nim
@@ -0,0 +1,53 @@
+# To run this, cd to the git repo root, and run "nim r nimdoc/booketester.nim".
+# to change expected results (after carefully verifying everything), use -d:nimTestsNimdocFixup
+
+import strutils, os
+from std/private/gitutils import diffFiles
+
+const fixup = defined(nimTestsNimdocFixup)
+
+var
+  failures = 0
+
+const
+  prjDir = "nimdoc" / "bookproject"
+  expDir = "expected"
+  outDir =  "book"
+
+proc exec(cmd: string) =
+  if execShellCmd(cmd) != 0:
+    quit("FAILURE: " & cmd)
+
+proc testNimBook(fixup = false) =
+  putEnv("SOURCE_DATE_EPOCH", "100000")
+  const nimExe = getCurrentCompilerExe()
+
+  exec("$1 doc --index:on --project --outdir:$2 $3" % [nimExe,
+                                                       prjDir / outDir / "api",
+                                                       prjDir / "code1.nim"])
+  exec("$1 book --index:only --outdir:$2 $3" % [nimExe, prjDir / outDir, prjDir])
+  exec("$1 book --outdir:$2 $3" % [nimExe, prjDir / outDir, prjDir])
+
+  for expected in walkDirRec(prjDir / expDir, checkDir=true):
+    let versionCacheParam = "?v=" & $NimMajor & "." & $NimMinor & "." & $NimPatch
+    let produced = expected.replace('\\', '/').replace("/$1/" % [expDir], "/$1/" % [outDir])
+    if not fileExists(produced):
+      echo "FAILURE: files not found: ", produced
+      inc failures
+    let producedFile = readFile(produced).replace(versionCacheParam,"")
+    if readFile(expected) != producedFile:
+      echo "FAILURE: files differ: ", produced
+      echo diffFiles(expected, produced).output
+      inc failures
+      if fixup:
+        writeFile(expected, producedFile)
+    else:
+      echo "SUCCESS: files identical: ", produced
+
+  if failures == 0:
+    removeDir(prjDir / outDir)
+
+testNimBook(fixup)
+
+if failures > 0:
+  quit "$# failures occurred; see note in nimdoc/tester.nim regarding -d:nimTestsNimdocFixup" %  $failures
--- a/nimdoc/extlinks/project/expected/_._/util.html
+++ b/nimdoc/extlinks/project/expected/_._/util.html
@@ -31,28 +31,34 @@
      <div class="row">
  <div class="three columns">
    <div class="theme-select-wrapper">
-      <label for="theme-select">Theme:&nbsp;</label>
-      <select id="theme-select" onchange="setTheme(this.value)">
-        <option value="auto">🌗 Match OS</option>
-        <option value="dark">🌑 Dark</option>
-        <option value="light">🌕 Light</option>
-      </select>
-    </div>
+  <label for="theme-select">Theme:&nbsp;</label>
+  <select id="theme-select" onchange="setTheme(this.value)">
+    <option value="auto">🌗 Match OS</option>
+    <option value="dark">🌑 Dark</option>
+    <option value="light">🌕 Light</option>
+  </select>
+</div>
+
    <div id="global-links">
-      <ul class="simple">
-        <li><a id="indexLink" href="../theindex.html">Index</a></li>
-      </ul>
-    </div>
-    <div id="searchInputDiv">
-      Search: <input type="search" id="searchInput" oninput="search()"/>
-    </div>
-    <div>
-      Group by:
-      <select onchange="groupBy(this.value)">
-        <option value="section">Section</option>
-        <option value="type">Type</option>
-      </select>
-    </div>
+  
+  <ul class="simple">
+  <li><a id="indexLink" href="../theindex.html">Index</a></li>
+</ul>
+
+</div>
+
+      <div id="searchInputDiv">
+  Search: <input type="search" id="searchInput" oninput="search()"/>
+</div>
+
+    <div class="search-groupby">
+  Group by:
+  <select onchange="groupBy(this.value)">
+    <option value="section">Section</option>
+    <option value="type">Type</option>
+  </select>
+</div>
+
    <ul class="simple simple-toc" id="toc-list">
  <li>
  <details open>
--- a/nimdoc/extlinks/project/expected/main.html
+++ b/nimdoc/extlinks/project/expected/main.html
@@ -31,28 +31,34 @@
      <div class="row">
  <div class="three columns">
    <div class="theme-select-wrapper">
-      <label for="theme-select">Theme:&nbsp;</label>
-      <select id="theme-select" onchange="setTheme(this.value)">
-        <option value="auto">🌗 Match OS</option>
-        <option value="dark">🌑 Dark</option>
-        <option value="light">🌕 Light</option>
-      </select>
-    </div>
+  <label for="theme-select">Theme:&nbsp;</label>
+  <select id="theme-select" onchange="setTheme(this.value)">
+    <option value="auto">🌗 Match OS</option>
+    <option value="dark">🌑 Dark</option>
+    <option value="light">🌕 Light</option>
+  </select>
+</div>
+
    <div id="global-links">
-      <ul class="simple">
-        <li><a id="indexLink" href="theindex.html">Index</a></li>
-      </ul>
-    </div>
-    <div id="searchInputDiv">
-      Search: <input type="search" id="searchInput" oninput="search()"/>
-    </div>
-    <div>
-      Group by:
-      <select onchange="groupBy(this.value)">
-        <option value="section">Section</option>
-        <option value="type">Type</option>
-      </select>
-    </div>
+  
+  <ul class="simple">
+  <li><a id="indexLink" href="theindex.html">Index</a></li>
+</ul>
+
+</div>
+
+      <div id="searchInputDiv">
+  Search: <input type="search" id="searchInput" oninput="search()"/>
+</div>
+
+    <div class="search-groupby">
+  Group by:
+  <select onchange="groupBy(this.value)">
+    <option value="section">Section</option>
+    <option value="type">Type</option>
+  </select>
+</div>
+
    <ul class="simple simple-toc" id="toc-list">
  <li><a class="reference" id="my-heading_toc" href="#my-heading">my heading</a></li>
 <li>
--- a/nimdoc/extlinks/project/expected/sub/submodule.html
+++ b/nimdoc/extlinks/project/expected/sub/submodule.html
@@ -31,28 +31,34 @@
      <div class="row">
  <div class="three columns">
    <div class="theme-select-wrapper">
-      <label for="theme-select">Theme:&nbsp;</label>
-      <select id="theme-select" onchange="setTheme(this.value)">
-        <option value="auto">🌗 Match OS</option>
-        <option value="dark">🌑 Dark</option>
-        <option value="light">🌕 Light</option>
-      </select>
-    </div>
+  <label for="theme-select">Theme:&nbsp;</label>
+  <select id="theme-select" onchange="setTheme(this.value)">
+    <option value="auto">🌗 Match OS</option>
+    <option value="dark">🌑 Dark</option>
+    <option value="light">🌕 Light</option>
+  </select>
+</div>
+
    <div id="global-links">
-      <ul class="simple">
-        <li><a id="indexLink" href="../theindex.html">Index</a></li>
-      </ul>
-    </div>
-    <div id="searchInputDiv">
-      Search: <input type="search" id="searchInput" oninput="search()"/>
-    </div>
-    <div>
-      Group by:
-      <select onchange="groupBy(this.value)">
-        <option value="section">Section</option>
-        <option value="type">Type</option>
-      </select>
-    </div>
+  
+  <ul class="simple">
+  <li><a id="indexLink" href="../theindex.html">Index</a></li>
+</ul>
+
+</div>
+
+      <div id="searchInputDiv">
+  Search: <input type="search" id="searchInput" oninput="search()"/>
+</div>
+
+    <div class="search-groupby">
+  Group by:
+  <select onchange="groupBy(this.value)">
+    <option value="section">Section</option>
+    <option value="type">Type</option>
+  </select>
+</div>
+
    <ul class="simple simple-toc" id="toc-list">
  <li>
  <details open>
--- a/nimdoc/rst2html/expected/rst_examples.html
+++ b/nimdoc/rst2html/expected/rst_examples.html
@@ -31,28 +31,27 @@
      <div class="row">
  <div class="three columns">
    <div class="theme-select-wrapper">
-      <label for="theme-select">Theme:&nbsp;</label>
-      <select id="theme-select" onchange="setTheme(this.value)">
-        <option value="auto">🌗 Match OS</option>
-        <option value="dark">🌑 Dark</option>
-        <option value="light">🌕 Light</option>
-      </select>
-    </div>
+  <label for="theme-select">Theme:&nbsp;</label>
+  <select id="theme-select" onchange="setTheme(this.value)">
+    <option value="auto">🌗 Match OS</option>
+    <option value="dark">🌑 Dark</option>
+    <option value="light">🌕 Light</option>
+  </select>
+</div>
+
    <div id="global-links">
-      <ul class="simple">
-        <li><a id="indexLink" href="theindex.html">Index</a></li>
-      </ul>
-    </div>
-    <div id="searchInputDiv">
-      Search: <input type="search" id="searchInput" oninput="search()"/>
-    </div>
-    <div>
-      Group by:
-      <select onchange="groupBy(this.value)">
-        <option value="section">Section</option>
-        <option value="type">Type</option>
-      </select>
-    </div>
+  
+  <ul class="simple">
+  <li><a id="indexLink" href="theindex.html">Index</a></li>
+</ul>
+
+</div>
+
+      <div id="searchInputDiv">
+  Search: <input type="search" id="searchInput" oninput="search()"/>
+</div>
+
+    
    <ul class="simple simple-toc" id="toc-list">
  <li><a class="reference" id="about-this-document_toc" href="#about-this-document">About this document</a></li>
 <ul class="simple"><li><a class="reference" id="about-this-document-encoding_toc" href="#about-this-document-encoding">Encoding</a></li>
--- a/nimdoc/test_doctype/expected/test_doctype.html
+++ b/nimdoc/test_doctype/expected/test_doctype.html
@@ -31,28 +31,34 @@
      <div class="row">
  <div class="three columns">
    <div class="theme-select-wrapper">
-      <label for="theme-select">Theme:&nbsp;</label>
-      <select id="theme-select" onchange="setTheme(this.value)">
-        <option value="auto">🌗 Match OS</option>
-        <option value="dark">🌑 Dark</option>
-        <option value="light">🌕 Light</option>
-      </select>
-    </div>
+  <label for="theme-select">Theme:&nbsp;</label>
+  <select id="theme-select" onchange="setTheme(this.value)">
+    <option value="auto">🌗 Match OS</option>
+    <option value="dark">🌑 Dark</option>
+    <option value="light">🌕 Light</option>
+  </select>
+</div>
+
    <div id="global-links">
-      <ul class="simple">
-        <li><a id="indexLink" href="theindex.html">Index</a></li>
-      </ul>
-    </div>
-    <div id="searchInputDiv">
-      Search: <input type="search" id="searchInput" oninput="search()"/>
-    </div>
-    <div>
-      Group by:
-      <select onchange="groupBy(this.value)">
-        <option value="section">Section</option>
-        <option value="type">Type</option>
-      </select>
-    </div>
+  
+  <ul class="simple">
+  <li><a id="indexLink" href="theindex.html">Index</a></li>
+</ul>
+
+</div>
+
+      <div id="searchInputDiv">
+  Search: <input type="search" id="searchInput" oninput="search()"/>
+</div>
+
+    <div class="search-groupby">
+  Group by:
+  <select onchange="groupBy(this.value)">
+    <option value="section">Section</option>
+    <option value="type">Type</option>
+  </select>
+</div>
+
    <ul class="simple simple-toc" id="toc-list">
  <li><a class="reference" id="check_toc" href="#check">Check</a></li>
 <li><a class="reference" id="text_toc" href="#text">text</a></li>
--- a/nimdoc/test_out_index_dot_html/expected/index.html
+++ b/nimdoc/test_out_index_dot_html/expected/index.html
@@ -31,28 +31,34 @@
      <div class="row">
  <div class="three columns">
    <div class="theme-select-wrapper">
-      <label for="theme-select">Theme:&nbsp;</label>
-      <select id="theme-select" onchange="setTheme(this.value)">
-        <option value="auto">🌗 Match OS</option>
-        <option value="dark">🌑 Dark</option>
-        <option value="light">🌕 Light</option>
-      </select>
-    </div>
+  <label for="theme-select">Theme:&nbsp;</label>
+  <select id="theme-select" onchange="setTheme(this.value)">
+    <option value="auto">🌗 Match OS</option>
+    <option value="dark">🌑 Dark</option>
+    <option value="light">🌕 Light</option>
+  </select>
+</div>
+
    <div id="global-links">
-      <ul class="simple">
-        <li><a id="indexLink" href="theindex.html">Index</a></li>
-      </ul>
-    </div>
-    <div id="searchInputDiv">
-      Search: <input type="search" id="searchInput" oninput="search()"/>
-    </div>
-    <div>
-      Group by:
-      <select onchange="groupBy(this.value)">
-        <option value="section">Section</option>
-        <option value="type">Type</option>
-      </select>
-    </div>
+  
+  <ul class="simple">
+  <li><a id="indexLink" href="theindex.html">Index</a></li>
+</ul>
+
+</div>
+
+      <div id="searchInputDiv">
+  Search: <input type="search" id="searchInput" oninput="search()"/>
+</div>
+
+    <div class="search-groupby">
+  Group by:
+  <select onchange="groupBy(this.value)">
+    <option value="section">Section</option>
+    <option value="type">Type</option>
+  </select>
+</div>
+
    <ul class="simple simple-toc" id="toc-list">
  <li>
  <details open>
--- a/nimdoc/testproject/expected/nimdoc.out.css
+++ b/nimdoc/testproject/expected/nimdoc.out.css
@@ -553,6 +553,11 @@ ul.nested-toc-section {
 ul.nested-toc-section > li {
  margin-left: 1.25em; }

+ul.simple-toc-section a.current,
+ul.nested-toc-section a.current {
+  font-weight: bold;
+  color: var(--anchor-focus);
+}

 ol.arabic {
  list-style: decimal; }
@@ -1139,3 +1144,7 @@ span.pragmawrap {
 span.attachedType {
  display: none;
  visibility: hidden; }
+
+summary {
+  cursor: pointer;
+}
--- a/nimdoc/testproject/expected/subdir/subdir_b/utils.html
+++ b/nimdoc/testproject/expected/subdir/subdir_b/utils.html
@@ -31,28 +31,34 @@
      <div class="row">
  <div class="three columns">
    <div class="theme-select-wrapper">
-      <label for="theme-select">Theme:&nbsp;</label>
-      <select id="theme-select" onchange="setTheme(this.value)">
-        <option value="auto">🌗 Match OS</option>
-        <option value="dark">🌑 Dark</option>
-        <option value="light">🌕 Light</option>
-      </select>
-    </div>
+  <label for="theme-select">Theme:&nbsp;</label>
+  <select id="theme-select" onchange="setTheme(this.value)">
+    <option value="auto">🌗 Match OS</option>
+    <option value="dark">🌑 Dark</option>
+    <option value="light">🌕 Light</option>
+  </select>
+</div>
+
    <div id="global-links">
-      <ul class="simple">
-        <li><a id="indexLink" href="../../theindex.html">Index</a></li>
-      </ul>
-    </div>
-    <div id="searchInputDiv">
-      Search: <input type="search" id="searchInput" oninput="search()"/>
-    </div>
-    <div>
-      Group by:
-      <select onchange="groupBy(this.value)">
-        <option value="section">Section</option>
-        <option value="type">Type</option>
-      </select>
-    </div>
+  
+  <ul class="simple">
+  <li><a id="indexLink" href="../../theindex.html">Index</a></li>
+</ul>
+
+</div>
+
+      <div id="searchInputDiv">
+  Search: <input type="search" id="searchInput" oninput="search()"/>
+</div>
+
+    <div class="search-groupby">
+  Group by:
+  <select onchange="groupBy(this.value)">
+    <option value="section">Section</option>
+    <option value="type">Type</option>
+  </select>
+</div>
+
    <ul class="simple simple-toc" id="toc-list">
  <li><a class="reference" id="this-is-now-a-header_toc" href="#this-is-now-a-header">This is now a header</a></li>
 <ul class="simple"><li><a class="reference" id="this-is-now-a-header-next-header_toc" href="#this-is-now-a-header-next-header">Next header</a></li>
--- a/nimdoc/testproject/expected/testproject.html
+++ b/nimdoc/testproject/expected/testproject.html
@@ -31,28 +31,34 @@
      <div class="row">
  <div class="three columns">
    <div class="theme-select-wrapper">
-      <label for="theme-select">Theme:&nbsp;</label>
-      <select id="theme-select" onchange="setTheme(this.value)">
-        <option value="auto">🌗 Match OS</option>
-        <option value="dark">🌑 Dark</option>
-        <option value="light">🌕 Light</option>
-      </select>
-    </div>
+  <label for="theme-select">Theme:&nbsp;</label>
+  <select id="theme-select" onchange="setTheme(this.value)">
+    <option value="auto">🌗 Match OS</option>
+    <option value="dark">🌑 Dark</option>
+    <option value="light">🌕 Light</option>
+  </select>
+</div>
+
    <div id="global-links">
-      <ul class="simple">
-        <li><a id="indexLink" href="theindex.html">Index</a></li>
-      </ul>
-    </div>
-    <div id="searchInputDiv">
-      Search: <input type="search" id="searchInput" oninput="search()"/>
-    </div>
-    <div>
-      Group by:
-      <select onchange="groupBy(this.value)">
-        <option value="section">Section</option>
-        <option value="type">Type</option>
-      </select>
-    </div>
+  
+  <ul class="simple">
+  <li><a id="indexLink" href="theindex.html">Index</a></li>
+</ul>
+
+</div>
+
+      <div id="searchInputDiv">
+  Search: <input type="search" id="searchInput" oninput="search()"/>
+</div>
+
+    <div class="search-groupby">
+  Group by:
+  <select onchange="groupBy(this.value)">
+    <option value="section">Section</option>
+    <option value="type">Type</option>
+  </select>
+</div>
+
    <ul class="simple simple-toc" id="toc-list">
  <li><a class="reference" id="basic-usage_toc" href="#basic-usage">Basic usage</a></li>
 <ul class="simple"><li><a class="reference" id="basic-usage-encoding-data_toc" href="#basic-usage-encoding-data">Encoding data</a></li>
--- a/tests/stdlib/trstgen.nim
+++ b/tests/stdlib/trstgen.nim
@@ -1307,6 +1307,36 @@ Test1
    doAssert "endOfNote</div>" in output3
    doAssert "class=\"admonition admonition-info\"" in output3

+    let input4 = dedent"""
+      .. admonition::
+        :title: Custom title
+        :collapsible:
+
+        endOfAdmonition
+    """
+
+    let output4 = input4.toHtml(
+      NoSandboxOpts
+    )
+    doAssert "Custom title</b></span></summary>" in output4
+    doAssert "<details open>" in output4
+    doAssert "endOfAdmonition</details></div>" in output4
+
+    let input5 = dedent"""
+      .. admonition::
+        :title: Custom title
+        :collapsible: closed
+
+        endOfAdmonition
+    """
+
+    let output5 = input5.toHtml(
+      NoSandboxOpts
+    )
+    doAssert "Custom title</b></span></summary>" in output5
+    doAssert "<details>" in output5
+    doAssert "endOfAdmonition</details></div>" in output5
+
  test "RST internal links":
    let input1 = dedent """
      Start.