fix(md/fmt/parser): bom, quotes, trimming by ematipico · Pull Request #10040 · biomejs/biome

ematipico · 2026-04-18T23:15:20Z

Summary

This PR improves markdown formatting and parsing.

I used Claude Code to navigate and implement the fixes. I reviewed the code and improved.

Parser

Fixes an issue where ordered lists such as 1. Foo weren't correctly parsed. The indentation wasn't parsed, and fell together with their text. This is fixed and you could see it in the snapsthost.

It also adds parsing for BOM.

Formatter

Fixes a case of idempotency when there's wasn't a line break in the file.
Now we add a line break between a code block and a paragraph, if there wasn't.

Test Plan

Added new tests

Docs

changeset-bot · 2026-04-18T23:15:26Z

⚠️ No Changeset found

Latest commit: c342d61

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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github-actions · 2026-04-18T23:19:29Z

Parser conformance results on

js/262

Test result	`main` count	This PR count	Difference
Total	53184	53184	0
Passed	51966	51966	0
Failed	1176	1176	0
Panics	42	42	0
Coverage	97.71%	97.71%	0.00%

jsx/babel

Test result	`main` count	This PR count	Difference
Total	38	38	0
Passed	37	37	0
Failed	1	1	0
Panics	0	0	0
Coverage	97.37%	97.37%	0.00%

markdown/commonmark

Test result	`main` count	This PR count	Difference
Total	652	652	0
Passed	652	652	0
Failed	0	0	0
Panics	0	0	0
Coverage	100.00%	100.00%	0.00%

symbols/microsoft

Test result	`main` count	This PR count	Difference
Total	5467	5467	0
Passed	1915	1915	0
Failed	3552	3552	0
Panics	0	0	0
Coverage	35.03%	35.03%	0.00%

ts/babel

Test result	`main` count	This PR count	Difference
Total	640	640	0
Passed	569	569	0
Failed	71	71	0
Panics	0	0	0
Coverage	88.91%	88.91%	0.00%

ts/microsoft

Test result	`main` count	This PR count	Difference
Total	18876	18876	0
Passed	13010	13010	0
Failed	5865	5865	0
Panics	1	1	0
Coverage	68.92%	68.92%	0.00%

coderabbitai · 2026-04-18T23:21:22Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 274f68c6-eae9-4d31-a514-e720f64ce49d

📥 Commits

Reviewing files that changed from the base of the PR and between bd1e74f and 695a4a1.

⛔ Files ignored due to path filters (33)

crates/biome_markdown_formatter/tests/specs/markdown/blockquote_code_block.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_formatter/tests/specs/markdown/bom.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_formatter/tests/specs/markdown/no_trailing_newline.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_formatter/tests/specs/markdown/ordered_lists.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_formatter/tests/specs/prettier/markdown/blockquote/code.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_formatter/tests/specs/prettier/markdown/spec/example-259.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/blockquote_inside_list.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/bom.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/bullet_list.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/fenced_code_in_list.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/hard_break_in_list_item.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/hard_break_nested_quote_in_list.md.snap is excluded by !**/*.snap and included by **
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/html_block_in_list.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/indented_code_in_list_vs_continuation.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/lazy_continuation.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/lazy_continuation_at_marker_indent.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/list_blank_lines_between_items.md.snap is excluded by !**/*.snap and included by **
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crates/biome_markdown_parser/tests/md_test_suite/ok/list_indentation.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/list_interrupt_bullet.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/list_interrupt_ordered.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/list_marker_trailing_spaces.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/list_tightness.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/multiline_list.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/nested_bullet_indent_tokens.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/nested_list_double_blank.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/nested_list_interrupt_after_newline.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/ordered_list.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/paragraph_interruption.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/quote_textual_marker_parity.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/setext_heading_edge_cases.md.snap is excluded by !**/*.snap and included by **
crates/biome_markdown_parser/tests/md_test_suite/ok/setext_heading_inside_list.md.snap is excluded by !**/*.snap and included by **

📒 Files selected for processing (13)

crates/biome_markdown_formatter/src/markdown/auxiliary/document.rs
crates/biome_markdown_formatter/src/markdown/lists/block_list.rs
crates/biome_markdown_formatter/tests/quick_test.rs
crates/biome_markdown_formatter/tests/specs/markdown/blockquote_code_block.md
crates/biome_markdown_formatter/tests/specs/markdown/bom.md
crates/biome_markdown_formatter/tests/specs/markdown/no_trailing_newline.md
crates/biome_markdown_formatter/tests/specs/markdown/ordered_lists.md
crates/biome_markdown_parser/src/lexer/mod.rs
crates/biome_markdown_parser/src/syntax/list.rs
crates/biome_markdown_parser/src/syntax/mod.rs
crates/biome_markdown_parser/tests/md_test_suite/ok/bom.md
crates/biome_markdown_syntax/src/block_ext.rs
crates/biome_markdown_syntax/src/lib.rs

Walkthrough

The PR refines Markdown formatting and parsing across the formatter and parser. Changes include conditional trailing newline handling in document formatting based on content inspection, improved block list formatting with enhanced quote-prefix and newline-block handling, a new lexer context for ordered list post-marker whitespace, and BOM support in lexing and parsing. New helper methods (is_fenced_block() and is_newline()) are added to AnyMdBlock to support these improvements, alongside test fixtures for edge cases like BOM, trailing newlines, and list formatting.

Possibly related PRs

feat(md/fmt): better formatting for some cases #9917 — Modifies document and block list formatter logic, changing how trimming and trailing hard line breaks are handled.
test(markdown): add regression tests for mixed list markers across blank lines #9732 — Updates Markdown list parsing logic in the same list.rs module that this PR modifies.
refactor(markdown): emit continuation indent as structural CST node #9737 — Changes how newline-like blocks are represented in the formatter and introduces similar helper utilities for block type detection.

Suggested labels

A-Parser, A-Formatter, L-Markdown

Suggested reviewers

dyc3

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the three main changes: BOM support, quote handling, and trimming fixes in the markdown formatter/parser.
Description check	✅ Passed	The description is directly related to the changeset, covering parser improvements (ordered list parsing, BOM support) and formatter fixes (idempotency, line break insertion).

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

Create PR with unit tests
Commit unit tests in branch fix/md-formatter-various

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

codspeed-hq · 2026-04-18T23:21:54Z

Merging this PR will not alter performance

✅ 28 untouched benchmarks
⏩ 228 skipped benchmarks¹

_{Comparing fix/md-formatter-various (c342d61) with main (46a77d0)}

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. ↩

ematipico · 2026-04-28T12:59:58Z

Going to merge this, since it's been open for a while.

fix(md/fmt/parser): bom, quotes, trimming

695a4a1

github-actions Bot added A-Parser Area: parser A-Formatter Area: formatter L-Markdown Language: Markdown labels Apr 18, 2026

ematipico requested review from a team April 18, 2026 23:16

Merge branch 'main' into fix/md-formatter-various

c342d61

ematipico merged commit 0e5a014 into main Apr 28, 2026
28 checks passed

ematipico deleted the fix/md-formatter-various branch April 28, 2026 13:00

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fix(md/fmt/parser): bom, quotes, trimming#10040

fix(md/fmt/parser): bom, quotes, trimming#10040
ematipico merged 2 commits intomainfrom
fix/md-formatter-various

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Summary

Parser

Formatter

Test Plan

Docs

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⚠️ No Changeset found

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Parser conformance results on

js/262

jsx/babel

markdown/commonmark

symbols/microsoft

ts/babel

ts/microsoft

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coderabbitai Bot commented Apr 18, 2026

Walkthrough

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Merging this PR will not alter performance

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ematipico commented Apr 28, 2026

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