Inlay hints support (#22896)

This adds inlay hints support to nimsuggest. It adds a new command to
nimsuggest, called 'inlayHints'.

Currently, it provides type information to 'var' and 'let' variables. In
the future, inlay hints can also be added for 'const' and for function
parameters. The protocol also reserves space for a tooltip field, which
is not used, yet, but support for it can be added in the future, without
further changing the protocol.

The change includes refactoring to allow the 'inlayHints' command to
return a completely different structure, compared to the other
nimsuggest commands. This will allow other future commands to have
custom return types as well. All the previous commands return the same
structure as before, so perfect backwards compatibility is maintained.

To use this feature, an update to the nim language server, as well as
the VS code extension is needed.

Related PRs:
nimlangserver: https://github.com/nim-lang/langserver/pull/53
VS code extension: https://github.com/saem/vscode-nim/pull/134

---------

Co-authored-by: Andreas Rumpf <rumpf_a@web.de>

compiler/ast.nim

@@ -903,6 +903,7 @@ type
     info*: TLineInfo
     when defined(nimsuggest):
       endInfo*: TLineInfo
+      hasUserSpecifiedType*: bool  # used for determining whether to display inlay type hints
     owner*: PSym
     flags*: TSymFlags
     ast*: PNode               # syntax tree of proc, iterator, etc.:

compiler/modulegraphs.nim

@@ -57,6 +57,7 @@ type
   SymInfoPair* = object
     sym*: PSym
     info*: TLineInfo
+    isDecl*: bool
 
   PipelinePass* = enum
     NonePass

compiler/options.nim

@@ -199,7 +199,7 @@ type
   IdeCmd* = enum
     ideNone, ideSug, ideCon, ideDef, ideUse, ideDus, ideChk, ideChkFile, ideMod,
     ideHighlight, ideOutline, ideKnown, ideMsg, ideProject, ideGlobalSymbols,
-    ideRecompile, ideChanged, ideType, ideDeclaration, ideExpand
+    ideRecompile, ideChanged, ideType, ideDeclaration, ideExpand, ideInlayHints
 
   Feature* = enum  ## experimental features; DO NOT RENAME THESE!
     dotOperators,
@@ -288,9 +288,24 @@ type
     version*: int
     endLine*: uint16
     endCol*: int
+    inlayHintInfo*: SuggestInlayHint
 
   Suggestions* = seq[Suggest]
 
+  SuggestInlayHintKind* = enum
+    sihkType = "Type",
+    sihkParameter = "Parameter"
+
+  SuggestInlayHint* = ref object
+    kind*: SuggestInlayHintKind
+    line*: int                   # Starts at 1
+    column*: int                 # Starts at 0
+    label*: string
+    paddingLeft*: bool
+    paddingRight*: bool
+    allowInsert*: bool
+    tooltip*: string
+
   ProfileInfo* = object
     time*: float
     count*: int
@@ -1071,6 +1086,7 @@ proc `$`*(c: IdeCmd): string =
   of ideRecompile: "recompile"
   of ideChanged: "changed"
   of ideType: "type"
+  of ideInlayHints: "inlayHints"
 
 proc floatInt64Align*(conf: ConfigRef): int16 =
   ## Returns either 4 or 8 depending on reasons.

compiler/semstmts.nim

@@ -672,9 +672,11 @@ proc semVarOrLet(c: PContext, n: PNode, symkind: TSymKind): PNode =
       addToVarSection(c, result, b)
       continue
 
+    var hasUserSpecifiedType = false
     var typ: PType = nil
     if a[^2].kind != nkEmpty:
       typ = semTypeNode(c, a[^2], nil)
+      hasUserSpecifiedType = true
 
     var typFlags: TTypeAllowedFlags = {}
 
@@ -746,6 +748,8 @@ proc semVarOrLet(c: PContext, n: PNode, symkind: TSymKind): PNode =
           addToVarSection(c, result, n, a)
           continue
         var v = semIdentDef(c, a[j], symkind, false)
+        when defined(nimsuggest):
+          v.hasUserSpecifiedType = hasUserSpecifiedType
         styleCheckDef(c, v)
         onDef(a[j].info, v)
         if sfGenSym notin v.flags:

compiler/suggest.nim

@@ -107,7 +107,7 @@ proc getTokenLenFromSource(conf: ConfigRef; ident: string; info: TLineInfo): int
       result = 0
   elif ident[0] in linter.Letters and ident[^1] != '=':
     result = identLen(line, column)
-    if cmpIgnoreStyle(line[column..column + result - 1], ident) != 0:
+    if cmpIgnoreStyle(line[column..column + result - 1], ident[0..min(result-1,len(ident)-1)]) != 0:
       result = 0
   else:
     var sourceIdent: string = ""
@@ -177,7 +177,7 @@ proc symToSuggest*(g: ModuleGraph; s: PSym, isLocal: bool, section: IdeCmd, info
     result.filePath = toFullPath(g.config, infox)
     result.line = toLinenumber(infox)
     result.column = toColumn(infox)
-    result.tokenLen = if section != ideHighlight:
+    result.tokenLen = if section notin {ideHighlight, ideInlayHints}:
                         s.name.s.len
                       else:
                         getTokenLenFromSource(g.config, s.name.s, infox)
@@ -185,50 +185,82 @@ proc symToSuggest*(g: ModuleGraph; s: PSym, isLocal: bool, section: IdeCmd, info
   result.endLine = endLine
   result.endCol = endCol
 
-proc `$`*(suggest: Suggest): string =
-  result = $suggest.section
+proc `$`*(suggest: SuggestInlayHint): string =
+  result = $suggest.kind
   result.add(sep)
-  if suggest.section == ideHighlight:
-    if suggest.symkind.TSymKind == skVar and suggest.isGlobal:
-      result.add("skGlobalVar")
-    elif suggest.symkind.TSymKind == skLet and suggest.isGlobal:
-      result.add("skGlobalLet")
+  result.add($suggest.line)
+  result.add(sep)
+  result.add($suggest.column)
+  result.add(sep)
+  result.add(suggest.label)
+  result.add(sep)
+  result.add($suggest.paddingLeft)
+  result.add(sep)
+  result.add($suggest.paddingRight)
+  result.add(sep)
+  result.add($suggest.allowInsert)
+  result.add(sep)
+  result.add(suggest.tooltip)
+
+proc `$`*(suggest: Suggest): string =
+  if suggest.section == ideInlayHints:
+    result = $suggest.inlayHintInfo
+  else:
+    result = $suggest.section
+    result.add(sep)
+    if suggest.section == ideHighlight:
+      if suggest.symkind.TSymKind == skVar and suggest.isGlobal:
+        result.add("skGlobalVar")
+      elif suggest.symkind.TSymKind == skLet and suggest.isGlobal:
+        result.add("skGlobalLet")
+      else:
+        result.add($suggest.symkind.TSymKind)
+      result.add(sep)
+      result.add($suggest.line)
+      result.add(sep)
+      result.add($suggest.column)
+      result.add(sep)
+      result.add($suggest.tokenLen)
     else:
       result.add($suggest.symkind.TSymKind)
-    result.add(sep)
-    result.add($suggest.line)
-    result.add(sep)
-    result.add($suggest.column)
-    result.add(sep)
-    result.add($suggest.tokenLen)
-  else:
-    result.add($suggest.symkind.TSymKind)
-    result.add(sep)
-    if suggest.qualifiedPath.len != 0:
-      result.add(suggest.qualifiedPath.join("."))
-    result.add(sep)
-    result.add(suggest.forth)
-    result.add(sep)
-    result.add(suggest.filePath)
-    result.add(sep)
-    result.add($suggest.line)
-    result.add(sep)
-    result.add($suggest.column)
-    result.add(sep)
-    when defined(nimsuggest) and not defined(noDocgen) and not defined(leanCompiler):
-      result.add(suggest.doc.escape)
-    if suggest.version == 0 or suggest.version == 3:
       result.add(sep)
-      result.add($suggest.quality)
-      if suggest.section == ideSug:
+      if suggest.qualifiedPath.len != 0:
+        result.add(suggest.qualifiedPath.join("."))
+      result.add(sep)
+      result.add(suggest.forth)
+      result.add(sep)
+      result.add(suggest.filePath)
+      result.add(sep)
+      result.add($suggest.line)
+      result.add(sep)
+      result.add($suggest.column)
+      result.add(sep)
+      when defined(nimsuggest) and not defined(noDocgen) and not defined(leanCompiler):
+        result.add(suggest.doc.escape)
+      if suggest.version == 0 or suggest.version == 3:
         result.add(sep)
-        result.add($suggest.prefix)
+        result.add($suggest.quality)
+        if suggest.section == ideSug:
+          result.add(sep)
+          result.add($suggest.prefix)
 
-  if (suggest.version == 3 and suggest.section in {ideOutline, ideExpand}):
-    result.add(sep)
-    result.add($suggest.endLine)
-    result.add(sep)
-    result.add($suggest.endCol)
+    if (suggest.version == 3 and suggest.section in {ideOutline, ideExpand}):
+      result.add(sep)
+      result.add($suggest.endLine)
+      result.add(sep)
+      result.add($suggest.endCol)
+
+proc suggestToSuggestInlayHint*(sug: Suggest): SuggestInlayHint =
+  SuggestInlayHint(
+    kind: sihkType,
+    line: sug.line,
+    column: sug.column + sug.tokenLen,
+    label: ": " & sug.forth,
+    paddingLeft: false,
+    paddingRight: false,
+    allowInsert: true,
+    tooltip: ""
+  )
 
 proc suggestResult*(conf: ConfigRef; s: Suggest) =
   if not isNil(conf.suggestionResultHook):
@@ -537,7 +569,7 @@ proc suggestSym*(g: ModuleGraph; info: TLineInfo; s: PSym; usageSym: var PSym; i
   ## misnamed: should be 'symDeclared'
   let conf = g.config
   when defined(nimsuggest):
-    g.suggestSymbols.mgetOrPut(info.fileIndex, @[]).add SymInfoPair(sym: s, info: info)
+    g.suggestSymbols.mgetOrPut(info.fileIndex, @[]).add SymInfoPair(sym: s, info: info, isDecl: isDecl)
 
     if conf.suggestVersion == 0:
       if s.allUsages.len == 0:

nimsuggest/nimsuggest.nim

@@ -161,7 +161,7 @@ proc listEpc(): SexpNode =
     argspecs = sexp("file line column dirtyfile".split(" ").map(newSSymbol))
     docstring = sexp("line starts at 1, column at 0, dirtyfile is optional")
   result = newSList()
-  for command in ["sug", "con", "def", "use", "dus", "chk", "mod", "globalSymbols", "recompile", "saved", "chkFile", "declaration"]:
+  for command in ["sug", "con", "def", "use", "dus", "chk", "mod", "globalSymbols", "recompile", "saved", "chkFile", "declaration", "inlayHints"]:
     let
       cmd = sexp(command)
       methodDesc = newSList()
@@ -506,6 +506,7 @@ proc execCmd(cmd: string; graph: ModuleGraph; cachedMsgs: CachedMsgs) =
   of "chkfile": conf.ideCmd = ideChkFile
   of "recompile": conf.ideCmd = ideRecompile
   of "type": conf.ideCmd = ideType
+  of "inlayhints": conf.ideCmd = ideInlayHints
   else: err()
   var dirtyfile = ""
   var orig = ""
@@ -774,6 +775,18 @@ proc findSymData(graph: ModuleGraph, trackPos: TLineInfo):
       result[] = s
       break
 
+func isInRange*(current, startPos, endPos: TLineInfo, tokenLen: int): bool =
+  result = current.fileIndex == startPos.fileIndex and
+    (current.line > startPos.line or (current.line == startPos.line and current.col>=startPos.col)) and
+    (current.line < endPos.line or (current.line == endPos.line and current.col <= endPos.col))
+
+proc findSymDataInRange(graph: ModuleGraph, startPos, endPos: TLineInfo):
+    seq[SymInfoPair] =
+  result = newSeq[SymInfoPair]()
+  for s in graph.fileSymbols(startPos.fileIndex).deduplicateSymInfoPair:
+    if isInRange(s.info, startPos, endPos, s.sym.name.s.len):
+      result.add(s)
+
 proc findSymData(graph: ModuleGraph, file: AbsoluteFile; line, col: int):
     ref SymInfoPair =
   let
@@ -781,6 +794,14 @@ proc findSymData(graph: ModuleGraph, file: AbsoluteFile; line, col: int):
     trackPos = newLineInfo(fileIdx, line, col)
   result = findSymData(graph, trackPos)
 
+proc findSymDataInRange(graph: ModuleGraph, file: AbsoluteFile; startLine, startCol, endLine, endCol: int):
+    seq[SymInfoPair] =
+  let
+    fileIdx = fileInfoIdx(graph.config, file)
+    startPos = newLineInfo(fileIdx, startLine, startCol)
+    endPos = newLineInfo(fileIdx, endLine, endCol)
+  result = findSymDataInRange(graph, startPos, endPos)
+
 proc markDirtyIfNeeded(graph: ModuleGraph, file: string, originalFileIdx: FileIndex) =
   let sha = $sha1.secureHashFile(file)
   if graph.config.m.fileInfos[originalFileIdx.int32].hash != sha or graph.config.ideCmd == ideSug:
@@ -803,6 +824,23 @@ proc suggestResult(graph: ModuleGraph, sym: PSym, info: TLineInfo,
                              endLine = endLine, endCol = endCol)
   suggestResult(graph.config, suggest)
 
+proc suggestInlayHintResult(graph: ModuleGraph, sym: PSym, info: TLineInfo,
+                   defaultSection = ideNone, endLine: uint16 = 0, endCol = 0) =
+  let section = if defaultSection != ideNone:
+                  defaultSection
+                elif sym.info.exactEquals(info):
+                  ideDef
+                else:
+                  ideUse
+  var suggestDef = symToSuggest(graph, sym, isLocal=false, section,
+                                info, 100, PrefixMatch.None, false, 0, true,
+                                endLine = endLine, endCol = endCol)
+  suggestDef.inlayHintInfo = suggestToSuggestInlayHint(suggestDef)
+  suggestDef.section = ideInlayHints
+  if sym.kind == skForVar:
+    suggestDef.inlayHintInfo.allowInsert = false
+  suggestResult(graph.config, suggestDef)
+
 const
   # kinds for ideOutline and ideGlobalSymbols
   searchableSymKinds = {skField, skEnumField, skIterator, skMethod, skFunc, skProc, skConverter, skTemplate}
@@ -910,7 +948,7 @@ proc executeNoHooksV3(cmd: IdeCmd, file: AbsoluteFile, dirtyfile: AbsoluteFile,
       graph.markDirtyIfNeeded(dirtyFile.string, fileInfoIdx(conf, file))
 
   # these commands require fully compiled project
-  if cmd in {ideUse, ideDus, ideGlobalSymbols, ideChk} and graph.needsCompilation():
+  if cmd in {ideUse, ideDus, ideGlobalSymbols, ideChk, ideInlayHints} and graph.needsCompilation():
     graph.recompilePartially()
     # when doing incremental build for the project root we should make sure that
     # everything is unmarked as no longer beeing dirty in case there is no
@@ -1066,6 +1104,19 @@ proc executeNoHooksV3(cmd: IdeCmd, file: AbsoluteFile, dirtyfile: AbsoluteFile,
 
     graph.markDirty fileIndex
     graph.markClientsDirty fileIndex
+  of ideInlayHints:
+    myLog fmt "Executing inlayHints"
+    var endLine = 0
+    var endCol = -1
+    var i = 0
+    i += skipWhile(tag, seps, i)
+    i += parseInt(tag, endLine, i)
+    i += skipWhile(tag, seps, i)
+    i += parseInt(tag, endCol, i)
+    let s = graph.findSymDataInRange(file, line, col, endLine, endCol)
+    for q in s:
+      if q.sym.kind in {skLet, skVar, skForVar} and q.isDecl and not q.sym.hasUserSpecifiedType:
+        graph.suggestInlayHintResult(q.sym, q.info, ideInlayHints)
   else:
     myLog fmt "Discarding {cmd}"