Support inline code diff notation

[tannerlinsley]

What changed

• Parse trailing [!code ++] and [!code --] directives at the Markdown adapter boundary.
• Remove directives before tokenization and copying.
• Emit th-line--inserted and th-line--deleted decorations.
• Support line, block, hash, and HTML comment forms.
• Document and test the behavior.

Why

TanStack docs already use Shiki's inline diff notation. The new Highlight renderer treated those directives as literal source, leaking them into rendered and copied code.

Validation

• pnpm run verify
• 46 tests passed
• Package, docs, size, and benchmark checks passed

Summary by CodeRabbit

• New Features
  • Added inline code-diff notation using [!code ++] and [!code --] markers.
  • Code examples now display inserted and deleted line styling while removing markers from copied and rendered code.
  • Supports JavaScript, shell/Python, and HTML comment formats.
  • Added documentation for parsing and rendering inline code differences.

[coderabbitai]

📝 Walkthrough

Walkthrough

Inline ++ and -- code directives are parsed into line decorations, removed before highlighting and copying, merged with existing fence annotations, and covered by parser, fence-rendering, and adapter tests.

Changes

Inline code diff notation

Layer / File(s)	Summary
Notation parser and contract src/markdown.ts, docs/reference/markdown.md, docs/guides/annotations.md, test/adapters.test.ts	Adds parseCodeDiffNotation, supports multiple comment syntaxes, strips directives, and returns inserted/deleted line decorations with unit coverage.
Code-fence decoration merging src/markdown.ts, docs/reference/markdown.md, test/adapters.test.ts	Merges inline, metadata, and explicit decorations while rendering cleaned code and validating inserted-line markup.
Highlighter integration src/markdown.ts, test/adapters.test.ts	Tokenizes notation-stripped code, includes inline decorations with highlighted lines, and validates deleted-line markup without raw directives.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant MarkdownInput
  participant parseCodeDiffNotation
  participant renderCodeFence
  participant TanStackMarkdownHighlighter
  MarkdownInput->>parseCodeDiffNotation: Provide code with inline diff directives
  parseCodeDiffNotation-->>renderCodeFence: Return cleaned code and line decorations
  renderCodeFence->>TanStackMarkdownHighlighter: Pass cleaned code and merged decorations
  TanStackMarkdownHighlighter-->>MarkdownInput: Return highlighted markup without directives

Loading

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise and accurately reflects the main change: adding support for inline code diff notation.
Description check	✅ Passed	The description covers the behavior, motivation, and validation, though it uses different headings than the template.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch taren/fix-code-diff-notation

---

_{Comment @coderabbitai help to get the list of available commands.}

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/markdown.ts`:
- Around line 149-155: Update the decoration assembly in the markdown rendering
flow around parseCodeDiffNotation and parseCodeFenceMeta to preserve mappings
for stripped directive spans and rebase caller-provided range decorations from
the original code onto the cleaned text before combining them. Keep parsed and
annotated decorations intact, and add coverage for a range on a line following a
removed directive to verify it renders at the corrected offset.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 26c77796-82ab-4ef8-ac32-972ff4f9a8c2

📥 Commits

Reviewing files that changed from the base of the PR and between 0f355b6 and 45649ac.

📒 Files selected for processing (4)

• docs/guides/annotations.md
• docs/reference/markdown.md
• src/markdown.ts
• test/adapters.test.ts

[coderabbitai]

🎯 Functional Correctness | 🟠 Major | 🏗️ Heavy lift

Rebase range decorations after stripping directives.

decorations can contain character-range offsets for the original code. Removing a directive shifts all later offsets, so caller-provided range decorations render on the wrong text. Preserve removed-span mappings and rebase range decorations before rendering; add coverage for a range on a line after a directive.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/markdown.ts` around lines 149 - 155, Update the decoration assembly in
the markdown rendering flow around parseCodeDiffNotation and parseCodeFenceMeta
to preserve mappings for stripped directive spans and rebase caller-provided
range decorations from the original code onto the cleaned text before combining
them. Keep parsed and annotated decorations intact, and add coverage for a range
on a line following a removed directive to verify it renders at the corrected
offset.