Fix infinite loop on plain-text diffs

[dimfeld]

Description

Rendering a diff with language "text" or "ansi" would cause an infinite loop, because those languages are skipped in getSharedHighlighter and so never become attached.

This change updates areLanguagesAttached to always return true for those languages, to match the corresponding special treatment of those languages in other places.

Motivation & Context

Infinite loop when rendering "text" diffs. I specifically saw this on a .gitignore diff in my project using the Vanilla JS API. This diff had no attached language but the autodetection chose "text" as the language.

Excerpt of the stack trace:

  rerender (FileDiff.js:287)
  (anonymous) (FileDiff.js:76)
  onHighlightSuccess (DiffHunksRenderer.js:275)
  (anonymous) (DiffHunksRenderer.js:224)
  Promise.then
  renderDiff (DiffHunksRenderer.js:222)
  render (FileDiff.js:353)
  rerender (FileDiff.js:287)
  (anonymous) (FileDiff.js:76)
  onHighlightSuccess (DiffHunksRenderer.js:275)
  (anonymous) (DiffHunksRenderer.js:224)
  Promise.then
  renderDiff (DiffHunksRenderer.js:222)
  render (FileDiff.js:353)
  rerender (FileDiff.js:287)

Type of changes

• Bug fix (non-breaking change which fixes an issue)
• Refactoring (non-breaking change)
• New feature (non-breaking change which adds functionality). You must have
  first discussed with the dev team and they should be aware that this PR is
  being opened
• Breaking change (fix or feature that would change existing functionality).
  You must have first discussed with the dev team and they should be aware
  that this PR is being opened
• Documentation update

Checklist

• I have read the
  contributing guidelines
• My code follows the code style of the project (bun run lint)
• My code is formatted properly (bun run format)
• [N/A] I have updated the documentation accordingly (if applicable)
• I have added tests to cover my changes (if applicable)
• All new and existing tests pass (bun run diffs:test) -- Used cd packages/diffs && bun run test since diffs:test command doesn't seem to exist.

How was AI used in generating this PR

Fed the above stack trace into Codex, which diagnosed the error and generated the fix and tests.

I manually reviewed all changes and verified that it fixes the problem in my application.

Related issues

[vercel]

@dimfeld is attempting to deploy a commit to the Pierre Computer Company Team on Vercel.

A member of the Team first needs to authorize it.

[wladimiiir]

I am experiencing the same issue: #534 that is being fixed by this PR.

Alternative fix might be by adding the 'text' and 'ansi' to the list of AttachedLanguages inside packages/diffs/src/highlighter/shared_highlighter.ts.

  // 'text' and 'ansi' are loaded during highlighter creation but skipped in
  // the language loop below. Track them as attached so areLanguagesAttached()
  // returns the correct value.
  AttachedLanguages.add('text');
  AttachedLanguages.add('ansi');

[vercel]

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Project	Deployment	Actions	Updated (UTC)
pierrejs-diff-demo	Ready	Preview	Apr 19, 2026 6:23pm
pierrejs-docs	Ready	Preview	Apr 19, 2026 6:23pm

[amadeus]

Great catch, and thanks for the fix, will merge when everything passes! 🙏

Also sorry, totally missed this PR the other day when you opened it.