[MichaReiser]

Summary

When source maps are disabled and the Bloom filter rules out comments on a node, the formatter can call fmt_fields directly. This skips cloning the comment handle and writing empty leading and trailing comments. Nodes with possible comments or source maps still take the existing path.

Compared with #29852, the fast path used 4.44% fewer instructions across Ruff’s five formatter benchmarks and 2.79% fewer across ten Python standard-library modules. Synthetic assignments with leading and trailing comments used 0.13% more. These are medians from 21 paired arm64 trials that include trivia construction and printing.

Test Plan

The formatter tests passed, and the parent and this change produced identical formatted text and source-map markers across the comparison corpora.

[astral-automations-bot]

ruff-ecosystem results

Formatter (stable)

✅ ecosystem check detected no format changes.

Formatter (preview)

✅ ecosystem check detected no format changes.

Formatter (stable) · Formatter (preview)

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Results for 7d4a67d · Workflow run

[codspeed]

Merging this PR will improve performance by 5.16%

1 warning

⚠️ 5 benchmarks with a significant change ran on different hardware

Their base and head results were measured on machines with a different CPU, core count or memory, so the changes might not come from the code. Run base and head on the same runner type.

Learn more about Macro Runners

See affected benchmarks

⚡ 5 improved benchmarks
✅ 55 untouched benchmarks
⏩ 238 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	CPU Simulation	formatter[large/dataset.py]	15.7 ms	14.8 ms	+6.01%
⚡	CPU Simulation	formatter[pydantic/types.py]	6.3 ms	6 ms	+5.54%
⚡	CPU Simulation	formatter[unicode/pypinyin.py]	1.2 ms	1.1 ms	+4.96%
⚡	CPU Simulation	formatter[numpy/ctypeslib.py]	3.3 ms	3.1 ms	+4.71%
⚡	CPU Simulation	formatter[numpy/globals.py]	433.9 µs	414.9 µs	+4.59%

Tip

Curious why performance improved? Comment @codspeedbot explain why performance improved on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing micha/formatter-fast-fmt-fields (7d4a67d) with micha/formatter-comment-bloom-filter (5140094)}

Footnotes

1. 238 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. ↩