RST: improve line blocks (#16518)

lib/packages/docutils/rst.nim

@@ -1147,7 +1147,8 @@ proc isAdornmentHeadline(p: RstParser, adornmentIdx: int): bool =
 proc isLineBlock(p: RstParser): bool =
   var j = tokenAfterNewline(p)
   result = currentTok(p).col == p.tok[j].col and p.tok[j].symbol == "|" or
-      p.tok[j].col > currentTok(p).col
+      p.tok[j].col > currentTok(p).col or
+      p.tok[j].symbol == "\n"
 
 proc predNL(p: RstParser): bool =
   result = true
@@ -1245,21 +1246,28 @@ proc whichSection(p: RstParser): RstNodeKind =
 
 proc parseLineBlock(p: var RstParser): PRstNode =
   result = nil
-  if nextTok(p).kind == tkWhite:
+  if nextTok(p).kind in {tkWhite, tkIndent}:
     var col = currentTok(p).col
     result = newRstNode(rnLineBlock)
-    pushInd(p, p.tok[p.idx + 2].col)
-    inc p.idx, 2
     while true:
       var item = newRstNode(rnLineBlockItem)
-      parseSection(p, item)
+      if nextTok(p).kind == tkWhite:
+        if nextTok(p).symbol.len > 1:  # pass additional indentation after '| '
+          item.text = nextTok(p).symbol
+        inc p.idx, 2
+        pushInd(p, p.tok[p.idx].col)
+        parseSection(p, item)
+        popInd(p)
+      else:  # tkIndent => add an empty line
+        item.text = "\n"
+        inc p.idx, 1
       result.add(item)
       if currentTok(p).kind == tkIndent and currentTok(p).ival == col and
-          nextTok(p).symbol == "|" and p.tok[p.idx + 2].kind == tkWhite:
-        inc p.idx, 3
+          nextTok(p).symbol == "|" and
+          p.tok[p.idx + 2].kind in {tkWhite, tkIndent}:
+        inc p.idx, 1
       else:
         break
-    popInd(p)
 
 proc parseParagraph(p: var RstParser, result: PRstNode) =
   while true:

lib/packages/docutils/rstast.nim

@@ -35,7 +35,8 @@ type
     rnOptionList, rnOptionListItem, rnOptionGroup, rnOption, rnOptionString,
     rnOptionArgument, rnDescription, rnLiteralBlock, rnQuotedLiteralBlock,
     rnLineBlock,              # the | thingie
-    rnLineBlockItem,          # sons of the | thing
+    rnLineBlockItem,          # a son of rnLineBlock - one line inside it.
+                              # When `RstNode` text="\n" the line's empty
     rnBlockQuote,             # text just indented
     rnTable, rnGridTable, rnMarkdownTable, rnTableRow, rnTableHeaderCell, rnTableDataCell,
     rnLabel,                  # used for footnotes and other things
@@ -73,7 +74,7 @@ type
     kind*: RstNodeKind       ## the node's kind
     text*: string             ## valid for leafs in the AST; and the title of
                               ## the document or the section; and rnEnumList
-                              ## and rnAdmonition
+                              ## and rnAdmonition; and rnLineBlockItem
     level*: int               ## valid for some node kinds
     sons*: RstNodeSeq        ## the node's sons
 

lib/packages/docutils/rstgen.nim

@@ -1160,9 +1160,21 @@ proc renderRstToOut(d: PDoc, n: PRstNode, result: var string) =
   of rnQuotedLiteralBlock:
     doAssert false, "renderRstToOut"
   of rnLineBlock:
-    renderAux(d, n, "<p>$1</p>", "$1\n\n", result)
+    if n.sons.len == 1 and n.sons[0].text == "\n":
+      # whole line block is one empty line, no need to add extra spacing
+      renderAux(d, n, "<p>$1</p> ", "\n\n$1", result)
+    else:  # add extra spacing around the line block for Latex
+      renderAux(d, n, "<p>$1</p>", "\n\\vspace{0.5em}\n$1\\vspace{0.5em}\n", result)
   of rnLineBlockItem:
-    renderAux(d, n, "$1<br />", "$1\\\\\n", result)
+    if n.text.len == 0:  # normal case - no additional indentation
+      renderAux(d, n, "$1<br/>", "\\noindent $1\n\n", result)
+    elif n.text == "\n":  # add one empty line
+      renderAux(d, n, "<br/>", "\\vspace{1em}\n", result)
+    else:  # additional indentation w.r.t. '| '
+      let indent = $(0.5 * (n.text.len - 1).toFloat) & "em"
+      renderAux(d, n,
+        "<span style=\"margin-left: " & indent & "\">$1</span><br/>",
+        "\\noindent\\hspace{" & indent & "}$1\n\n", result)
   of rnBlockQuote:
     renderAux(d, n, "<blockquote><p>$1</p></blockquote>\n",
                     "\\begin{quote}$1\\end{quote}\n", result)