[Repo Assist] fix: Markdown.ToMd preserves [body][key] form for unresolved indirect links (#1185)

* fix: Markdown.ToMd preserves [body][key] form for unresolved indirect links

Previously the unresolved-key fallback for IndirectLink used the second
field (original) as a direct-link URL, producing '[body](key)' which treats
the reference key as a URL. This was inconsistent with IndirectImage, which
preserves '![body][key]' when the key is unresolved.

Fix: split the two IndirectLink cases so the resolved path produces a direct
link '[body](url)' and the unresolved path preserves the indirect form
'[body][key]', matching IndirectImage behaviour.

Added test: 'ToMd preserves indirect link form when key is unresolved'
(347/347 Markdown tests pass).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* ci: trigger checks

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

RELEASE_NOTES.md

@@ -17,6 +17,7 @@
 * Fix `Markdown.ToMd` serialising `HorizontalRule` as 23 hyphens regardless of the character used in the source. It now emits exactly three characters matching the parsed character (`---`, `***`, or `___`), giving faithful round-trips.
 * Remove stray `printfn` debug output emitted to stdout when `Markdown.ToMd` encountered an unrecognised paragraph type.
 * Fix `Markdown.ToLatex` producing invalid LaTeX output for level-6 (and deeper) headings. Previously the LaTeX command was an empty string, resulting in bare `{content}` without a command prefix. Headings at level 6+ are now serialised as `\subparagraph{...}`, which is the deepest sectioning command available in LaTeX.
+* Fix `Markdown.ToMd` serialising unresolved indirect links as `[body](key)` (treating the reference key as a URL) instead of the correct `[body][key]` form. Unresolved indirect links are now preserved in their original indirect-reference form, consistent with how unresolved indirect images are handled.
 
 ### Added
 * Add tests for `Markdown.ToFsx` (direct serialisation to F# script format), which previously had no unit test coverage.

src/FSharp.Formatting.Markdown/MarkdownUtils.fs

@@ -113,8 +113,8 @@ module internal MarkdownUtils =
 
             "[" + formatSpans ctx body + "](" + link + t + ")"
 
-        | IndirectLink(body, _, LookupKey ctx.Links (link, _), _)
-        | IndirectLink(body, link, _, _) -> "[" + formatSpans ctx body + "](" + link + ")"
+        | IndirectLink(body, _, LookupKey ctx.Links (link, _), _) -> "[" + formatSpans ctx body + "](" + link + ")"
+        | IndirectLink(body, _, key, _) -> "[" + formatSpans ctx body + "][" + key + "]"
 
         | IndirectImage(body, _, LookupKey ctx.Links (link, _), _) -> sprintf "![%s](%s)" body link
         | IndirectImage(body, _, key, _) -> sprintf "![%s][%s]" body key

tests/FSharp.Markdown.Tests/Markdown.fs

@@ -1418,6 +1418,15 @@ let ``ToMd preserves an indirect link when key is not resolved`` () =
     result |> should contain "[link text]"
     result |> should contain "https://example.com"
 
+[<Test>]
+let ``ToMd preserves indirect link form when key is unresolved`` () =
+    // No reference definition → key cannot be resolved; should preserve [body][key] form
+    let input = "[link text][unknown-ref]"
+    let doc = Markdown.Parse(input)
+    let result = Markdown.ToMd(doc)
+    // Should preserve the indirect reference form, not produce a broken direct link
+    result |> should contain "[link text][unknown-ref]"
+
 // --------------------------------------------------------------------------------------
 // ToMd round-trip: indirect images (issue - failwith "tbd - IndirectImage")
 // --------------------------------------------------------------------------------------