fix: backslash newlines when copying from a code block

[nperez0111]

Summary

Copying content from inside a code block produced a clipboard payload littered with backslashes — every newline in text/plain was prefixed with \ (markdown's hard-break syntax), and text/html had <br> separators inside the code instead of literal newlines.

Reproduction: select code in a code block → paste into any plain-text app:

{\
abc: '34\
\
}

This PR fixes the root cause so both text/html and text/plain come out clean.

Rationale

Tracing the clipboard pipeline showed two compounding issues:

1. Inline-only export path was used for code-block selections. When the selection lives inside a single block, copyExtension takes a shortcut that strips the block wrapper — producing inline HTML for cleaner pastes. For paragraphs that's right; for code blocks it's wrong, because the <pre><code> wrapper carries semantic meaning. Without it, the markdown converter has no idea this is code and treats every line break as a paragraph hard-break (\ + newline).

2. serializeInlineContentExternalHTML re-introduced <br> for code content. It calls inlineContentToNodes without a blockType, which makes it split every \n into a hardBreak PM node. Those serialize as <br> — even when wrapped in <pre><code>. The internal-HTML serializer already passed blockType through; the external one didn't.

Changes

• copyExtension.ts — guard the inline-only optimization with a parent.type.spec.code check. Code-block selections fall through to the existing block-export path, which invokes the code block's own toExternalHTML (proper <pre><code class="language-X" data-language="X">).
• serializeBlocksExternalHTML.ts — plumb blockType through serializeInlineContentExternalHTML (via options.blockType) so inlineContentToNodes keeps \n as literal text for code-content blocks. serializeBlock passes block.type.
• tests/.../exportTestExecutors.ts — prettify(..., { ignore: ["code"] }) so code-block snapshots show real newlines instead of having them collapsed by the prettifier.
• tests/.../codeBlockMarkdown.test.ts — three regression tests: full code-block copy, partial selection within a code block, and a paragraph-copy guard to prove non-code paths are untouched.
• Snapshots: 3 code-block HTML snapshots regenerated to show literal newlines (no more <br /> inside <pre><code>).

Impact

After the fix, for the user's repro:

• text/html: `

  {
  
  abc: '34

}` — proper code semantics, real newlines.

• text/plain: clean fenced markdown block, no backslashes.

No behavior change for non-code blocks. The inline-only optimization for paragraphs, headings, etc. is preserved exactly.

Testing

• Added 3 regression tests in tests/src/unit/core/clipboard/copy/codeBlockMarkdown.test.ts (full code-block copy, partial selection, paragraph guard).
• Updated 3 code-block HTML snapshots (now show literal newlines instead of <br />).
• All 430 core unit tests pass.
• All 49 clipboard tests (copy, paste, copyPaste, copyPasteEquality) pass — confirming no regressions in paste behavior.
• The pre-existing failures in src/unit/nextjs/serverUtil and src/unit/react/BlockNoteView*Remount* are unrelated (fail on main too).

Checklist

• Code follows the project's coding standards.
• Unit tests covering the new feature have been added.
• All existing tests pass.
• The documentation has been updated to reflect the new feature — N/A, this is a bug fix with no API change.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes

  • Copying and exporting now correctly preserve code-block formatting and language metadata: exported HTML uses proper pre/code wrappers with language attributes and exported Markdown uses fenced code blocks without escaped newlines. Selections that are inline within non-code blocks are handled without stripping surrounding inline content, preventing accidental loss of formatting.

• Tests

  • Added regression tests to verify copy/export behavior for code and non-code blocks.

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Project	Deployment	Actions	Updated (UTC)
blocknote	Ready	Preview	May 5, 2026 3:26pm
blocknote-website	Ready	Preview	May 5, 2026 3:26pm

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: d79429ea-ee3e-4712-a2e8-d0ed362eb51f

📥 Commits

Reviewing files that changed from the base of the PR and between 9352e24 and eb3498b.

⛔ Files ignored due to path filters (3)

• tests/src/unit/core/formatConversion/export/__snapshots__/blocknoteHTML/codeBlock/contains-newlines.html is excluded by !**/__snapshots__/**
• tests/src/unit/core/formatConversion/export/__snapshots__/blocknoteHTML/codeBlock/empty.html is excluded by !**/__snapshots__/**
• tests/src/unit/core/formatConversion/export/__snapshots__/html/codeBlock/contains-newlines.html is excluded by !**/__snapshots__/**

📒 Files selected for processing (4)

• packages/core/src/api/clipboard/toClipboard/copyExtension.ts
• packages/core/src/api/exporters/html/util/serializeBlocksExternalHTML.ts
• tests/src/unit/core/clipboard/copy/codeBlockMarkdown.test.ts
• tests/src/unit/shared/formatConversion/export/exportTestExecutors.ts

✅ Files skipped from review due to trivial changes (1)

• tests/src/unit/core/clipboard/copy/codeBlockMarkdown.test.ts

🚧 Files skipped from review as they are similar to previous changes (3)

• tests/src/unit/shared/formatConversion/export/exportTestExecutors.ts
• packages/core/src/api/exporters/html/util/serializeBlocksExternalHTML.ts
• packages/core/src/api/clipboard/toClipboard/copyExtension.ts

---

📝 Walkthrough

Walkthrough

Determines when a selection is fully inline and whether its parent block is a code block; if inside a code block, inline wrapper-stripping is disabled. The originating block type is passed into inline HTML serialization. Tests added for code-block copy HTML/Markdown and prettify options adjusted for code preservation.

Changes

Code Block Copy Preservation

Layer / File(s)	Summary
Data Shape / API packages/core/src/api/exporters/html/util/serializeBlocksExternalHTML.ts	serializeInlineContentExternalHTML signature extended: options?: { document?: Document; blockType?: string }.
Core Logic: Selection Analysis packages/core/src/api/clipboard/toClipboard/copyExtension.ts	fragmentToExternalHTML now computes isFullyInline and parentIsCode and sets isWithinBlockContent = isFullyInline && !parentIsCode, changing when inline-only wrapper-stripping runs.
Core Logic: Serialization packages/core/src/api/exporters/html/util/serializeBlocksExternalHTML.ts	Calls to serializeInlineContentExternalHTML forward { ...options, blockType: block.type } so inline conversion can be block-type-aware (newline/code handling).
Test Helpers / Snapshots tests/src/unit/shared/formatConversion/export/exportTestExecutors.ts	Introduced PRETTIFY_OPTIONS = { tag_wrap: true, ignore: ["code"] } and replaced inline prettify options in HTML test helpers to preserve <code> content.
Behavioral Tests tests/src/unit/core/clipboard/copy/codeBlockMarkdown.test.ts	Added tests: copying from a codeBlock produces <pre><code> external HTML with language attributes and raw newlines and yields fenced code block markdown; copying from a paragraph remains unchanged.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Suggested reviewers

• matthewlipski

Poem

🐰 I hopped through fragments, sniffed each line,
Found code kept snug where fences shine.
I left the newlines, wrapped the tongue,
Copied code sings — a carrot-song sprung.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'fix: backslash newlines when copying from a code block' directly and specifically describes the bug being fixed—backslashes appearing in clipboard content when copying from code blocks—which is the main focus of the changeset.
Description check	✅ Passed	The PR description comprehensively covers all required template sections: Summary explains the bug, Rationale details root causes, Changes lists code modifications, Impact describes outcome, Testing documents verification, and Checklist is completed with appropriate N/A justification.
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.

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✨ 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 feat/fix-codeblock-copy

---

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commit: eb3498b