Fix snippet compiler reporting line numbers in specific cases

Author: KacperFKorban

scaladoc/src/dotty/tools/scaladoc/site/templates.scala

@@ -106,7 +106,7 @@ case class TemplateFile(
       // Snippet compiler currently supports markdown only
       val parser: Parser = Parser.builder(defaultMarkdownOptions).build()
       val parsedMd = parser.parse(rendered)
-      val processed = FlexmarkSnippetProcessor.processSnippets(parsedMd, snippetCheckingFunc, withContext = false)(using ssctx.outerCtx)
+      val processed = FlexmarkSnippetProcessor.processSnippets(parsedMd, None, snippetCheckingFunc, withContext = false)(using ssctx.outerCtx)
       HtmlRenderer.builder(defaultMarkdownOptions).build().render(processed)
 
     layoutTemplate match

scaladoc/src/dotty/tools/scaladoc/snippets/FlexmarkSnippetProcessor.scala

@@ -8,17 +8,18 @@ import com.vladsch.flexmark.util.options.MutableDataSet
 import collection.JavaConverters._
 
 import dotty.tools.scaladoc.tasty.comments.markdown.ExtendedFencedCodeBlock
+import dotty.tools.scaladoc.tasty.comments.PreparsedComment
 
 object FlexmarkSnippetProcessor:
-  def processSnippets(root: mdu.Node, checkingFunc: => SnippetChecker.SnippetCheckingFunc, withContext: Boolean)(using CompilerContext): mdu.Node = {
+  def processSnippets(root: mdu.Node, preparsed: Option[PreparsedComment], checkingFunc: => SnippetChecker.SnippetCheckingFunc, withContext: Boolean)(using CompilerContext): mdu.Node = {
     lazy val cf: SnippetChecker.SnippetCheckingFunc = checkingFunc
 
     val nodes = root.getDescendants().asScala.collect {
       case fcb: mda.FencedCodeBlock => fcb
     }.toList
 
     nodes.foldLeft[Map[String, String]](Map()) { (snippetMap, node) =>
-      val lineOffset = node.getStartLineNumber
+      val lineOffset = node.getStartLineNumber + preparsed.fold(0)(_.strippedLinesBeforeNo)
       val info = node.getInfo.toString.split(" ")
       if info.contains("scala") then {
         val argOverride = info

scaladoc/src/dotty/tools/scaladoc/snippets/SnippetChecker.scala

@@ -33,7 +33,7 @@ class SnippetChecker(val args: Scaladoc.Args)(using cctx: CompilerContext):
 
   // These constants were found empirically to make snippet compiler
   // report errors in the same position as main compiler.
-  private val constantLineOffset = 3
+  private val constantLineOffset = 2
   private val constantColumnOffset = 4
 
   def checkSnippet(

scaladoc/src/dotty/tools/scaladoc/snippets/SnippetCompilerSetting.scala

@@ -5,4 +5,4 @@ import dotty.tools.scaladoc.DocContext
 import dotty.tools.dotc.config.Settings._
 import dotty.tools.dotc.config.ScalaSettings
 
-case class SnippetCompilerSetting[T](setting: Setting[T], value: T)
+case class SnippetCompilerSetting[T](setting: Setting[T], value: T)

scaladoc/src/dotty/tools/scaladoc/tasty/comments/Comments.scala

@@ -67,6 +67,7 @@ case class PreparsedComment(
   hideImplicitConversions: List[String],
   shortDescription:        List[String],
   syntax:                  List[String],
+  strippedLinesBeforeNo:   Int,
 )
 
 case class DokkaCommentBody(summary: Option[DocPart], body: DocPart)
@@ -78,7 +79,7 @@ abstract class MarkupConversion[T](val repr: Repr)(using dctx: DocContext) {
   protected def markupToDokkaCommentBody(t: T): DokkaCommentBody
   protected def filterEmpty(xs: List[String]): List[T]
   protected def filterEmpty(xs: SortedMap[String, String]): SortedMap[String, T]
-  protected def processSnippets(t: T): T
+  protected def processSnippets(t: T, preparsed: PreparsedComment): T
 
   lazy val snippetChecker = dctx.snippetChecker
 
@@ -141,7 +142,7 @@ abstract class MarkupConversion[T](val repr: Repr)(using dctx: DocContext) {
 
   final def parse(preparsed: PreparsedComment): Comment =
     val markup = stringToMarkup(preparsed.body)
-    val body = markupToDokkaCommentBody(processSnippets(markup))
+    val body = markupToDokkaCommentBody(processSnippets(markup, preparsed))
     Comment(
       body                    = body.body,
       short                   = body.summary,
@@ -193,8 +194,8 @@ class MarkdownCommentParser(repr: Repr)(using dctx: DocContext)
       .filterNot { case (_, v) => v.isEmpty }
       .mapValues(stringToMarkup).to(SortedMap)
 
-  def processSnippets(root: mdu.Node): mdu.Node =
-    FlexmarkSnippetProcessor.processSnippets(root, snippetCheckingFunc(owner), withContext = true)
+  def processSnippets(root: mdu.Node, preparsed: PreparsedComment): mdu.Node =
+    FlexmarkSnippetProcessor.processSnippets(root, Some(preparsed), snippetCheckingFunc(owner), withContext = true)
 }
 
 class WikiCommentParser(repr: Repr)(using DocContext)
@@ -249,6 +250,6 @@ class WikiCommentParser(repr: Repr)(using DocContext)
     xs.view.mapValues(stringToMarkup).to(SortedMap)
       .filterNot { case (_, v) => v.blocks.isEmpty }
 
-  def processSnippets(root: wiki.Body): wiki.Body =
+  def processSnippets(root: wiki.Body, preparsed: PreparsedComment): wiki.Body =
     // Currently not supported
     root

scaladoc/src/dotty/tools/scaladoc/tasty/comments/Preparser.scala

@@ -32,8 +32,8 @@ object Preparser {
       tags: Map[TagKey, List[String]],
       lastTagKey: Option[TagKey],
       remaining: List[String],
-      inCodeBlock: Boolean
-    ): PreparsedComment = remaining match {
+      inCodeBlock: Boolean,
+    )(using strippedLinesBeforeNo: Int = 0): PreparsedComment = remaining match {
       case CodeBlockStartRegex(before, marker, after) :: ls if !inCodeBlock =>
         if (!before.trim.isEmpty && !after.trim.isEmpty && marker == "```")
           go(docBody, tags, lastTagKey, before :: (marker + after) :: ls, inCodeBlock = false)
@@ -108,7 +108,7 @@ object Preparser {
       case line :: ls =>
         if docBody.length > 0 then docBody.append(endOfLine)
         docBody.append(line)
-        go(docBody, tags, lastTagKey, ls, inCodeBlock)
+        go(docBody, tags, lastTagKey, ls, inCodeBlock)(using strippedLinesBeforeNo + (if line.isEmpty && docBody.length == 0 then 1 else 0))
 
 
       case Nil =>
@@ -177,6 +177,7 @@ object Preparser {
           hideImplicitConversions = allTags(SimpleTagKey("hideImplicitConversion")),
           shortDescription        = allTags(SimpleTagKey("shortDescription")),
           syntax                  = allTags(SimpleTagKey("syntax")),
+          strippedLinesBeforeNo   = strippedLinesBeforeNo
         )
 
         cmt