fix(markdown_parser): mixed bullet markers and lazy continuation in lists

[jfmcdowell]

Note

This PR was created with AI assistance (Claude Code).

Summary

Two fixes in crates/biome_markdown_parser/src/syntax/list.rs:

1. Mixed bullet markers don't split lists after non-paragraph content. BulletList::is_at_list_end had an early return that checked has_bullet_item_after_blank_lines_at_indent without checking whether the bullet marker changed. After headings, setext headings, and fenced code blocks, the item loop broke at a blank-introducing NEWLINE that hit this path, so - # H\n\n+ x merged into one <ul> instead of two. Added marker_changes_after_blank_lines to the early return.

2. Lazy continuation lines not absorbed into nested list items. check_continuation_indent returned Break unconditionally when indent < marker_indent, preventing lazy continuation below the marker column. Per CommonMark §5.2, - a\n - b\n lazy\nhello should keep hello inside the nested item. Now checks for lazy eligibility before breaking.

Note: - --- is a pre-existing markdown parser bug where it parses as a top-level thematic break instead of a list item containing <hr />; not addressed here.

Test Plan

• just test-crate biome_markdown_parser
• just test-markdown-conformance
• 8 targeted fuzz regression tests added to spec_test.rs
• 2 CST snapshots updated (header_in_list.md, thematic_break_in_list.md)

Docs

N/A

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Latest commit: 7751648

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[codspeed-hq]

Merging this PR will not alter performance

✅ 28 untouched benchmarks
⏩ 228 skipped benchmarks¹

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_{Comparing jfmcdowell:fix/md-parser-list-bugs (7751648) with main (1aa85f5)}

Footnotes

1. 228 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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📥 Commits

Reviewing files that changed from the base of the PR and between 1aa85f5 and 7751648.

⛔ Files ignored due to path filters (2)

• crates/biome_markdown_parser/tests/md_test_suite/ok/header_in_list.md.snap is excluded by !**/*.snap and included by **
• crates/biome_markdown_parser/tests/md_test_suite/ok/thematic_break_in_list.md.snap is excluded by !**/*.snap and included by **

📒 Files selected for processing (2)

• crates/biome_markdown_parser/src/syntax/list.rs
• crates/biome_markdown_parser/tests/spec_test.rs

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Walkthrough

This PR refines markdown list parsing to handle blank-line edge cases. It modifies BulletList::is_at_list_end to detect when bullet markers change across blank lines (forcing list boundaries) and updates check_continuation_indent to conditionally allow lazy continuation based on whether the next line starts a list item or contains a block interrupt. Additionally, comprehensive test cases validate mixed-marker scenarios and lazy-continuation behaviour against expected HTML output.

Possibly related PRs

• fix(markdown_parser): split bullet lists when marker type changes across blank lines #9785: Directly modifies BulletList::is_at_list_end to detect marker-type changes across blank lines for list splitting
• fix(markdown_parser): fix lazy continuation at nested list marker indent #9776: Adjusts check_continuation_indent's lazy-continuation guard logic around marker indent boundaries
• test(markdown): add regression tests for mixed list markers across blank lines #9732: Touches the same list blank-line handling code; the main PR's marker-change detection directly addresses the mixed-marker regressions tested there

Suggested reviewers

• ematipico
• dyc3

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title directly and clearly describes the main changes: fixing mixed bullet markers and lazy continuation handling in lists.
Description check	✅ Passed	The description is well-related to the changeset, detailing the two specific fixes, test plan, and noting a pre-existing bug not addressed.

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[ematipico]

These fixes will make the formatter's life easier

Almost there!

[jfmcdowell]

These fixes will make the formatter's life easier

Almost there!

The fuzzer is helping a ton!