Fix #693: add uppercase ConditionalDefines and strip marker lines from LiterateCode (#999)

- Add outputKind.Extension.ToUpperInvariant() to ConditionalDefines so both
  '#if HTML' and '#if html' (and equivalents for other output kinds) are supported
- Strip '#if SYMBOL' / '#endif // SYMBOL' marker lines from LiterateCode Line list
  before syntax-highlighting so they do not appear in formatted output
- Add tests covering both fixes

Co-authored-by: Repo Assist <repo-assist@github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Don Syme <dsyme@users.noreply.github.com>

Author: 4 people

RELEASE_NOTES.md

@@ -4,6 +4,8 @@
 
 ### Fixed
 * Improve error message when a named code snippet is not found (e.g. `(*** include:name ***)` with undefined name now reports the missing name clearly). [#982](https://github.com/fsprojects/FSharp.Formatting/pull/982)
+* Add uppercase output kind extension (e.g. `HTML`, `IPYNB`) to `ConditionalDefines` so that `#if HTML` and `(*** condition: HTML ***)` work alongside their lowercase variants. [#693](https://github.com/fsprojects/FSharp.Formatting/issues/693)
+* Strip `#if SYMBOL` / `#endif // SYMBOL` marker lines from `LiterateCode` source before syntax-highlighting so they do not appear in formatted output. [#693](https://github.com/fsprojects/FSharp.Formatting/issues/693)
 
 ### Changed
 * Update FCS to 43.10.100. [#935](https://github.com/fsprojects/FSharp.Formatting/pull/966)

src/FSharp.Formatting.Literate/Literate.fs

@@ -30,7 +30,7 @@ type Literate private () =
         mdlinkResolver
         tokenKindToCss
         =
-        let defines = [ outputKind.Extension ]
+        let defines = [ outputKind.Extension; outputKind.Extension.ToUpperInvariant() ]
 
         { Substitutions = substitutions
           GenerateLineNumbers = defaultArg lineNumbers true

src/FSharp.Formatting.Literate/Transformations.fs

@@ -553,7 +553,18 @@ module internal Transformations =
     let replaceLiterateParagraphs ctx (doc: LiterateDocument) =
         let codes = doc.Paragraphs |> List.collect collectLiterateCode
 
-        let snippets = [| for _, (lines, _) in codes -> Snippet("", lines) |]
+        // Strip #if SYMBOL / #endif // SYMBOL marker lines from code before syntax-highlighting,
+        // so that they don't appear in the formatted output.
+        let markerLines =
+            ctx.ConditionalDefines
+            |> List.collect (fun sym -> [ sprintf "#if %s" sym; sprintf "#endif // %s" sym ])
+            |> Set.ofList
+
+        let stripDefineLines (lines: Line list) =
+            lines
+            |> List.filter (fun (Line(originalLine, _)) -> not (markerLines.Contains(originalLine.Trim())))
+
+        let snippets = [| for _, (lines, _) in codes -> Snippet("", stripDefineLines lines) |]
 
         // Format all snippets and build lookup dictionary for parameters
         let formatted =

tests/FSharp.Literate.Tests/LiterateTests.fs

@@ -1768,6 +1768,101 @@ let ``Script transforms to markdown`` () =
     md |> shouldContainText "Another [hyperlink](simple2.md)"
     md |> shouldContainText "let hello ="
 
+[<Test>]
+let ``condition: HTML uppercase is included in HTML output and excluded from Pynb output`` () =
+    let content =
+        """
+let commonCode = 1
+(*** condition: HTML ***)
+let htmlOnlyCode = 2
+let moreCode = 3
+"""
+
+    let doc = Literate.ParseScriptString(content, "C" </> "test.fsx")
+    let html = Literate.ToHtml(doc)
+    let pynb = Literate.ToPynb(doc)
+
+    // (*** condition: HTML ***) with uppercase should be included in HTML output (fix 1)
+    html |> shouldContainText "htmlOnlyCode"
+    // And excluded from Pynb output
+    pynb |> shouldNotContainText "htmlOnlyCode"
+
+[<Test>]
+let ``condition: html lowercase is still included in HTML output`` () =
+    let content =
+        """
+let commonCode = 1
+(*** condition: html ***)
+let htmlOnlyCode = 2
+let moreCode = 3
+"""
+
+    let doc = Literate.ParseScriptString(content, "C" </> "test.fsx")
+    let html = Literate.ToHtml(doc)
+    let pynb = Literate.ToPynb(doc)
+
+    // (*** condition: html ***) with lowercase should still be included in HTML output
+    html |> shouldContainText "htmlOnlyCode"
+    // And excluded from Pynb output
+    pynb |> shouldNotContainText "htmlOnlyCode"
+
+[<Test>]
+let ``#if HTML and #endif // HTML marker lines are stripped from HTML LiterateCode output`` () =
+    let content =
+        """
+let alwaysVisible = 1
+#if HTML
+let insideHtmlBlock = 2
+#endif // HTML
+let alsoAlwaysVisible = 3
+"""
+
+    let doc = Literate.ParseScriptString(content, "C" </> "test.fsx")
+    let html = Literate.ToHtml(doc)
+
+    // The #if HTML / #endif // HTML marker lines themselves should not appear in HTML output.
+    // They would appear as <span class="pp">#if</span> tokens before this fix.
+    html |> shouldNotContainText ">#if<"
+    html |> shouldNotContainText ">#endif<"
+
+[<Test>]
+let ``#if HTML and #endif // HTML marker lines are not in Fsx but code inside is present`` () =
+    let content =
+        """
+let alwaysVisible = 1
+#if HTML
+let insideHtmlBlock = 2
+#endif // HTML
+let alsoAlwaysVisible = 3
+"""
+
+    let doc = Literate.ParseScriptString(content, "C" </> "test.fsx")
+    let fsx = Literate.ToFsx(doc)
+
+    // The code inside the #if HTML block does appear as-is in fsx output
+    // (only #if FSX / #endif // FSX marker lines are stripped for fsx output)
+    fsx |> shouldContainText "insideHtmlBlock"
+
+[<Test>]
+let ``#if IPYNB and #endif // IPYNB marker lines are stripped from Pynb LiterateCode output`` () =
+    let content =
+        """
+let alwaysVisible = 1
+#if IPYNB
+let insideIpynbBlock = 2
+#endif // IPYNB
+let alsoAlwaysVisible = 3
+"""
+
+    let doc = Literate.ParseScriptString(content, "C" </> "test.fsx")
+    let pynb = Literate.ToPynb(doc)
+
+    // The marker lines should not appear in Pynb output
+    pynb |> shouldNotContainText "#if IPYNB"
+    pynb |> shouldNotContainText "#endif // IPYNB"
+    // But the code inside should be present
+    pynb |> shouldContainText "insideIpynbBlock"
+
 // --------------------------------------------------------------------------------------
 // Emoji in FSX comments → HTML (Issue #964)
 // These tests verify that emoji characters are preserved throughout the full