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
  • Improved handling of code block content when copying or exporting selections within code blocks, ensuring raw text formatting is properly preserved instead of converting through intermediate HTML.
  • Enhanced block type information tracking during export serialization for more accurate content handling.