Preserve frozen comment spacing in auto-update

[j178]

Closes #1941
Closes #1944

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.14%. Comparing base (173faf5) to head (717e589).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1945      +/-   ##
==========================================
+ Coverage   92.11%   92.14%   +0.02%     
==========================================
  Files         112      112              
  Lines       23177    23235      +58     
==========================================
+ Hits        21350    21409      +59     
+ Misses       1827     1826       -1     

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[Copilot]

Pull request overview

Preserves existing whitespace before inline # frozen: comments when auto-update rewrites rev entries, improving formatting stability for users’ configs.

Changes:

• Add inline_comment_spacing() helper to extract/preserve whitespace before inline comments.
• Update TOML and YAML rewrite paths to reuse existing spacing (or default to two spaces) when emitting # frozen: comments.
• Add unit tests covering YAML default spacing and spacing preservation for existing frozen comments.

[prek-ci-bot]

📦 Cargo Bloat Comparison

Binary size change: +0.00% (25.7 MiB → 25.7 MiB)

Expand for cargo-bloat output

Head Branch Results

 File  .text     Size             Crate Name
 1.3%   2.6% 332.0KiB        aws_lc_sys aws_lc_0_39_1_aes_gcm_encrypt_avx512
 1.3%   2.6% 332.0KiB        aws_lc_sys aws_lc_0_39_1_aes_gcm_decrypt_avx512
 0.3%   0.7%  88.1KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.3%   0.6%  82.1KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.3%   0.6%  72.0KiB             prek? <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
 0.2%   0.4%  57.0KiB              prek prek::languages::<impl prek::config::Language>::install::{{closure}}
 0.2%   0.4%  52.5KiB annotate_snippets annotate_snippets::renderer::render::render
 0.2%   0.4%  46.6KiB              prek prek::run::{{closure}}
 0.2%   0.3%  42.0KiB              prek prek::cli::run::run::run::{{closure}}
 0.1%   0.3%  32.6KiB             prek? <prek::cli::RunArgs as clap_builder::derive::Args>::augment_args
 0.1%   0.2%  30.0KiB             prek? <prek::config::_::<impl serde_core::de::Deserialize for prek::config::Config>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map
 0.1%   0.2%  28.0KiB      serde_saphyr saphyr_parser_bw::scanner::Scanner<T>::fetch_more_tokens
 0.1%   0.2%  28.0KiB        aws_lc_sys aws_lc_0_39_1_edwards25519_scalarmuldouble_alt
 0.1%   0.2%  27.5KiB        aws_lc_sys aws_lc_0_39_1_edwards25519_scalarmuldouble
 0.1%   0.2%  27.1KiB              prek prek::cli::try_repo::try_repo::{{closure}}
 0.1%   0.2%  26.8KiB               std core::ptr::drop_in_place<prek::languages::<impl prek::config::Language>::install::{{closure}}>
 0.1%   0.2%  22.8KiB              prek prek::hooks::meta_hooks::MetaHooks::run::{{closure}}
 0.1%   0.2%  22.6KiB      serde_saphyr saphyr_parser_bw::scanner::Scanner<T>::fetch_more_tokens
 0.1%   0.2%  22.3KiB         [Unknown] Lp384_montjscalarmul_alt_p384_montjadd
 0.1%   0.2%  21.5KiB      clap_builder clap_builder::parser::parser::Parser::get_matches_with
41.8%  86.3%  10.8MiB                   And 24081 smaller methods. Use -n N to show more.
48.5% 100.0%  12.5MiB                   .text section size, the file size is 25.7MiB

Base Branch Results

 File  .text     Size             Crate Name
 1.3%   2.6% 332.0KiB        aws_lc_sys aws_lc_0_39_1_aes_gcm_encrypt_avx512
 1.3%   2.6% 332.0KiB        aws_lc_sys aws_lc_0_39_1_aes_gcm_decrypt_avx512
 0.3%   0.7%  87.6KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.3%   0.7%  85.4KiB             prek? <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
 0.3%   0.6%  82.1KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.2%   0.4%  57.0KiB              prek prek::languages::<impl prek::config::Language>::install::{{closure}}
 0.2%   0.4%  52.5KiB annotate_snippets annotate_snippets::renderer::render::render
 0.2%   0.4%  46.6KiB              prek prek::run::{{closure}}
 0.2%   0.3%  42.0KiB              prek prek::cli::run::run::run::{{closure}}
 0.1%   0.3%  32.4KiB             prek? <prek::cli::RunArgs as clap_builder::derive::Args>::augment_args
 0.1%   0.2%  30.0KiB             prek? <prek::config::_::<impl serde_core::de::Deserialize for prek::config::Config>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map
 0.1%   0.2%  28.0KiB      serde_saphyr saphyr_parser_bw::scanner::Scanner<T>::fetch_more_tokens
 0.1%   0.2%  28.0KiB        aws_lc_sys aws_lc_0_39_1_edwards25519_scalarmuldouble_alt
 0.1%   0.2%  27.5KiB        aws_lc_sys aws_lc_0_39_1_edwards25519_scalarmuldouble
 0.1%   0.2%  27.1KiB              prek prek::cli::try_repo::try_repo::{{closure}}
 0.1%   0.2%  26.8KiB               std core::ptr::drop_in_place<prek::languages::<impl prek::config::Language>::install::{{closure}}>
 0.1%   0.2%  22.8KiB              prek prek::hooks::meta_hooks::MetaHooks::run::{{closure}}
 0.1%   0.2%  22.6KiB      serde_saphyr saphyr_parser_bw::scanner::Scanner<T>::fetch_more_tokens
 0.1%   0.2%  22.3KiB         [Unknown] Lp384_montjscalarmul_alt_p384_montjadd
 0.1%   0.2%  21.5KiB      clap_builder clap_builder::parser::parser::Parser::get_matches_with
41.7%  86.1%  10.7MiB                   And 24071 smaller methods. Use -n N to show more.
48.5% 100.0%  12.4MiB                   .text section size, the file size is 25.7MiB

[prek-ci-bot]

⚡️ Hyperfine Benchmarks

Summary: 0 regressions, 0 improvements above the 10% threshold.

Environment

• OS: Linux 6.17.0-1010-azure
• CPU: 4 cores
• prek version: prek 0.3.9+6 (06c0030 2026-04-15)
• Rust version: rustc 1.94.1 (e408947bf 2026-03-25)
• Hyperfine version: hyperfine 1.20.0

CLI Commands

Benchmarking basic commands in the main repo:

prek --version

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base --version	2.3 ± 0.1	2.1	3.0	1.03 ± 0.07
prek-head --version	2.2 ± 0.1	2.1	2.6	1.00

prek list

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base list	9.9 ± 0.2	9.4	10.3	1.01 ± 0.04
prek-head list	9.7 ± 0.3	9.2	11.4	1.00

prek validate-config .pre-commit-config.yaml

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base validate-config .pre-commit-config.yaml	3.4 ± 0.1	3.3	3.6	1.03 ± 0.04
prek-head validate-config .pre-commit-config.yaml	3.3 ± 0.1	3.1	3.6	1.00

prek sample-config

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base sample-config	2.8 ± 0.1	2.7	3.1	1.08 ± 0.04
prek-head sample-config	2.6 ± 0.1	2.4	2.8	1.00

Cold vs Warm Runs

Comparing first run (cold) vs subsequent runs (warm cache):

prek run --all-files (cold - no cache)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --all-files	147.6 ± 4.3	139.7	152.7	1.00
prek-head run --all-files	148.3 ± 4.0	140.5	152.6	1.00 ± 0.04

prek run --all-files (warm - with cache)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --all-files	150.8 ± 4.1	144.6	157.1	1.00
prek-head run --all-files	155.3 ± 4.8	147.4	167.8	1.03 ± 0.04

Full Hook Suite

Running the builtin hook suite on the benchmark workspace:

prek run --all-files (full builtin hook suite)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --all-files	152.8 ± 4.2	145.9	165.3	1.01 ± 0.07
prek-head run --all-files	151.2 ± 9.0	137.2	203.6	1.00

Individual Hook Performance

Benchmarking each hook individually on the test repo:

prek run trailing-whitespace --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run trailing-whitespace --all-files	21.9 ± 0.8	20.7	23.5	1.00
prek-head run trailing-whitespace --all-files	22.0 ± 0.6	21.1	23.7	1.01 ± 0.04

prek run end-of-file-fixer --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run end-of-file-fixer --all-files	29.1 ± 2.4	24.9	34.1	1.00
prek-head run end-of-file-fixer --all-files	29.7 ± 2.0	25.8	32.7	1.02 ± 0.11

prek run check-json --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-json --all-files	12.5 ± 0.5	11.6	14.0	1.03 ± 0.05
prek-head run check-json --all-files	12.1 ± 0.4	11.4	13.0	1.00

prek run check-yaml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-yaml --all-files	12.1 ± 0.3	11.5	12.7	1.00
prek-head run check-yaml --all-files	12.1 ± 0.4	11.5	12.8	1.00 ± 0.04

prek run check-toml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-toml --all-files	12.7 ± 0.3	12.1	13.2	1.00 ± 0.05
prek-head run check-toml --all-files	12.7 ± 0.6	11.6	14.6	1.00

prek run check-xml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-xml --all-files	12.5 ± 0.4	12.0	13.3	1.04 ± 0.04
prek-head run check-xml --all-files	12.0 ± 0.3	11.5	12.8	1.00

prek run detect-private-key --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run detect-private-key --all-files	19.5 ± 1.7	16.3	23.9	1.01 ± 0.10
prek-head run detect-private-key --all-files	19.3 ± 1.1	17.0	21.2	1.00

prek run fix-byte-order-marker --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run fix-byte-order-marker --all-files	24.0 ± 2.0	20.4	28.6	1.04 ± 0.12
prek-head run fix-byte-order-marker --all-files	23.1 ± 1.9	19.7	27.0	1.00

Installation Performance

Benchmarking hook installation (fast path hooks skip Python setup):

prek install-hooks (cold - no cache)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base install-hooks	4.9 ± 0.1	4.7	5.1	1.07 ± 0.04
prek-head install-hooks	4.6 ± 0.1	4.4	4.7	1.00

prek install-hooks (warm - with cache)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base install-hooks	4.8 ± 0.1	4.7	4.8	1.05 ± 0.02
prek-head install-hooks	4.5 ± 0.0	4.5	4.6	1.00

File Filtering/Scoping Performance

Testing different file selection modes:

prek run (staged files only)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run	50.9 ± 0.9	49.3	52.4	1.00
prek-head run	51.5 ± 0.9	49.4	53.0	1.01 ± 0.03

prek run --files '*.json' (specific file type)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --files '*.json'	9.0 ± 0.1	8.7	9.3	1.01 ± 0.03
prek-head run --files '*.json'	9.0 ± 0.3	8.5	9.5	1.00

Workspace Discovery & Initialization

Benchmarking hook discovery and initialization overhead:

prek run --dry-run --all-files (measures init overhead)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --dry-run --all-files	13.6 ± 0.1	13.5	13.9	1.01 ± 0.01
prek-head run --dry-run --all-files	13.5 ± 0.2	13.1	13.7	1.00

Meta Hooks Performance

Benchmarking meta hooks separately:

prek run check-hooks-apply --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-hooks-apply --all-files	12.4 ± 0.2	12.1	13.0	1.00
prek-head run check-hooks-apply --all-files	12.7 ± 0.8	12.2	15.5	1.03 ± 0.07

prek run check-useless-excludes --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-useless-excludes --all-files	12.5 ± 0.2	12.3	12.8	1.00
prek-head run check-useless-excludes --all-files	12.8 ± 0.3	12.3	13.3	1.02 ± 0.03

prek run identity --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run identity --all-files	10.9 ± 0.3	10.5	11.6	1.01 ± 0.03
prek-head run identity --all-files	10.8 ± 0.2	10.5	11.2	1.00