Add file-contents-sorter as builtin hook

[j178]

Closes #1843

[Copilot]

Pull request overview

This PR adds a Rust-native implementation of the file-contents-sorter hook and wires it into both the pre-commit-hooks fast path and the repo: builtin hook set, including schema/docs/test updates. It also introduces an internal FilePattern::Never to support builtin hooks that should match no files by default (requiring users to set files: explicitly).

Changes:

• Implement file-contents-sorter (sorting + optional case-insensitive sort / unique mode) and hook it into the fast-path dispatcher.
• Add file-contents-sorter to builtin hooks (including list-builtins output), docs, and the generated JSON schema.
• Introduce FilePattern::Never for “match nothing by default” builtin-hook behavior.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
prek.schema.json	Adds file-contents-sorter to the schema’s builtin hook id list.
docs/builtin.md	Documents the new hook and its behavior/arguments.
crates/prek/tests/list_builtins.rs	Updates list-builtins snapshots to include the new hook.
crates/prek/tests/builtin_hooks.rs	Adds an integration test for the builtin file-contents-sorter behavior.
crates/prek/src/hooks/pre_commit_hooks/mod.rs	Registers the new hook in the pre-commit-hooks fast path enum/dispatcher.
crates/prek/src/hooks/pre_commit_hooks/file_contents_sorter.rs	New Rust implementation of the hook (with unit tests).
crates/prek/src/hooks/builtin_hooks/mod.rs	Adds builtin hook metadata + defaults (files: Never).
crates/prek/src/config.rs	Adds FilePattern::Never and tests for its matching behavior.

Comments suppressed due to low confidence (1)

crates/prek/src/hooks/builtin_hooks/mod.rs:275

• The builtin hook description is user-facing (list-builtins) but is grammatically incorrect and misleading: it says users must provide a "list of target files" as input, but the hook is targeted via the files: regex/glob configuration. Please reword to accurately describe configuration (e.g., that users must set files: explicitly because the default matches nothing) and fix capitalization/grammar.

                priority: None,
                options: HookOptions {
                    description: Some(
                        "ensures that a file is either empty, or ends with one newline."

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[prek-ci-bot]

📦 Cargo Bloat Comparison

Binary size change: +0.40% (25.0 MiB → 25.1 MiB)

Expand for cargo-bloat output

Head Branch Results

 File  .text     Size             Crate Name
 1.3%   2.7% 332.0KiB        aws_lc_sys aws_lc_0_39_0_aes_gcm_encrypt_avx512
 1.3%   2.7% 332.0KiB        aws_lc_sys aws_lc_0_39_0_aes_gcm_decrypt_avx512
 0.3%   0.7%  82.7KiB             prek? <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
 0.3%   0.7%  81.1KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.3%   0.6%  74.1KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.2%   0.5%  56.9KiB              prek prek::languages::<impl prek::config::Language>::install::{{closure}}
 0.2%   0.4%  51.0KiB annotate_snippets annotate_snippets::renderer::render::render
 0.2%   0.4%  47.1KiB              prek prek::run::{{closure}}
 0.2%   0.3%  41.8KiB              prek prek::cli::run::run::run::{{closure}}
 0.1%   0.3%  32.0KiB             prek? <prek::cli::RunArgs as clap_builder::derive::Args>::augment_args
 0.1%   0.2%  28.0KiB        aws_lc_sys aws_lc_0_39_0_edwards25519_scalarmuldouble_alt
 0.1%   0.2%  27.8KiB      serde_saphyr saphyr_parser_bw::scanner::Scanner<T>::fetch_more_tokens
 0.1%   0.2%  27.5KiB        aws_lc_sys aws_lc_0_39_0_edwards25519_scalarmuldouble
 0.1%   0.2%  26.2KiB              prek prek::cli::try_repo::try_repo::{{closure}}
 0.1%   0.2%  25.4KiB             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%  24.4KiB               std core::ptr::drop_in_place<prek::languages::<impl prek::config::Language>::install::{{closure}}>
 0.1%   0.2%  23.0KiB              prek prek::hooks::meta_hooks::MetaHooks::run::{{closure}}
 0.1%   0.2%  22.4KiB      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%  21.6KiB              prek prek::workspace::Project::init_hooks::{{closure}}
41.2%  85.9%  10.3MiB                   And 23547 smaller methods. Use -n N to show more.
48.0% 100.0%  12.0MiB                   .text section size, the file size is 25.1MiB

Base Branch Results

 File  .text     Size             Crate Name
 1.3%   2.7% 332.0KiB        aws_lc_sys aws_lc_0_39_0_aes_gcm_encrypt_avx512
 1.3%   2.7% 332.0KiB        aws_lc_sys aws_lc_0_39_0_aes_gcm_decrypt_avx512
 0.3%   0.7%  82.4KiB             prek? <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
 0.3%   0.7%  80.6KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.3%   0.6%  73.6KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.2%   0.5%  56.9KiB              prek prek::languages::<impl prek::config::Language>::install::{{closure}}
 0.2%   0.4%  51.0KiB annotate_snippets annotate_snippets::renderer::render::render
 0.2%   0.4%  46.4KiB              prek prek::run::{{closure}}
 0.2%   0.3%  41.8KiB              prek prek::cli::run::run::run::{{closure}}
 0.1%   0.3%  32.0KiB             prek? <prek::cli::RunArgs as clap_builder::derive::Args>::augment_args
 0.1%   0.2%  28.0KiB        aws_lc_sys aws_lc_0_39_0_edwards25519_scalarmuldouble_alt
 0.1%   0.2%  27.8KiB      serde_saphyr saphyr_parser_bw::scanner::Scanner<T>::fetch_more_tokens
 0.1%   0.2%  27.5KiB        aws_lc_sys aws_lc_0_39_0_edwards25519_scalarmuldouble
 0.1%   0.2%  25.8KiB              prek prek::cli::try_repo::try_repo::{{closure}}
 0.1%   0.2%  24.4KiB               std core::ptr::drop_in_place<prek::languages::<impl prek::config::Language>::install::{{closure}}>
 0.1%   0.2%  23.2KiB             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%  22.4KiB      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%  21.6KiB              prek prek::workspace::Project::init_hooks::{{closure}}
 0.1%   0.2%  21.5KiB      clap_builder clap_builder::parser::parser::Parser::get_matches_with
41.2%  85.9%  10.3MiB                   And 23471 smaller methods. Use -n N to show more.
47.9% 100.0%  12.0MiB                   .text section size, the file size is 25.0MiB

[prek-ci-bot]

⚡️ Hyperfine Benchmarks

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

Environment

• OS: Linux 6.14.0-1017-azure
• CPU: 4 cores
• prek version: prek 0.3.6+25 (fe45b38 2026-03-21)
• Rust version: rustc 1.94.0 (4a4ef493e 2026-03-02)
• 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	2.4 ± 0.1	2.3	2.7	1.00
prek-head --version	2.4 ± 0.1	2.2	3.0	1.00 ± 0.06

prek list

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base list	9.1 ± 0.1	8.9	9.6	1.00 ± 0.02
prek-head list	9.1 ± 0.1	8.9	9.5	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	3.3 ± 0.1	3.1	3.4	1.00 ± 0.03
prek-head validate-config .pre-commit-config.yaml	3.3 ± 0.1	3.1	3.5	1.00

prek sample-config

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base sample-config	2.7 ± 0.3	2.6	4.7	1.00 ± 0.11
prek-head sample-config	2.7 ± 0.1	2.6	2.9	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	159.9 ± 2.8	154.9	165.5	1.02 ± 0.02
prek-head run --all-files	157.2 ± 2.4	154.4	162.1	1.00

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

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --all-files	159.6 ± 2.9	155.2	165.5	1.01 ± 0.02
prek-head run --all-files	158.2 ± 2.3	154.4	162.8	1.00

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	158.9 ± 2.5	155.0	165.7	1.00
prek-head run --all-files	161.1 ± 13.1	155.0	233.2	1.01 ± 0.08

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	22.6 ± 0.6	21.3	23.8	1.02 ± 0.03
prek-head run trailing-whitespace --all-files	22.2 ± 0.4	21.6	23.1	1.00

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	28.8 ± 1.8	25.9	32.4	1.02 ± 0.08
prek-head run end-of-file-fixer --all-files	28.3 ± 1.3	25.9	30.8	1.00

prek run check-json --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-json --all-files	12.8 ± 0.5	12.1	14.0	1.03 ± 0.04
prek-head run check-json --all-files	12.5 ± 0.3	12.1	13.2	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 ± 0.2	11.8	12.8	1.00
prek-head run check-yaml --all-files	12.2 ± 0.3	11.8	13.3	1.01 ± 0.03

prek run check-toml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-toml --all-files	12.5 ± 0.4	12.0	14.0	1.02 ± 0.04
prek-head run check-toml --all-files	12.2 ± 0.3	11.7	12.9	1.00

prek run check-xml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-xml --all-files	12.3 ± 0.3	11.8	13.1	1.01 ± 0.03
prek-head run check-xml --all-files	12.1 ± 0.2	11.8	12.7	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	19.3 ± 1.3	17.0	22.7	1.03 ± 0.10
prek-head run detect-private-key --all-files	18.8 ± 1.2	16.9	21.1	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	24.4 ± 1.6	21.8	27.3	1.00 ± 0.09
prek-head run fix-byte-order-marker --all-files	24.4 ± 1.5	21.8	27.5	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	5.0 ± 0.1	4.9	5.2	1.02 ± 0.02
prek-head install-hooks	4.9 ± 0.1	4.9	5.0	1.00

prek install-hooks (warm - with cache)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base install-hooks	4.9 ± 0.0	4.9	5.0	1.00 ± 0.01
prek-head install-hooks	4.9 ± 0.0	4.9	5.0	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	53.4 ± 0.7	52.0	55.4	1.00
prek-head run	54.0 ± 1.1	52.6	55.9	1.01 ± 0.02

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

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --files '*.json'	9.2 ± 0.1	9.0	9.6	1.00
prek-head run --files '*.json'	9.2 ± 0.1	9.0	9.4	1.00 ± 0.02

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	14.3 ± 0.3	13.9	15.0	1.00 ± 0.02
prek-head run --dry-run --all-files	14.2 ± 0.2	14.0	14.6	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	14.4 ± 0.1	14.1	14.7	1.00 ± 0.01
prek-head run check-hooks-apply --all-files	14.4 ± 0.1	14.2	14.7	1.00

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

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-useless-excludes --all-files	14.1 ± 0.7	12.6	14.8	1.11 ± 0.05
prek-head run check-useless-excludes --all-files	12.7 ± 0.2	12.5	13.1	1.00

prek run identity --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run identity --all-files	11.2 ± 0.1	11.1	11.5	1.00
prek-head run identity --all-files	11.2 ± 0.1	11.1	11.4	1.00 ± 0.01

[codecov]

Codecov Report

❌ Patch coverage is 97.72727% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.88%. Comparing base (cb3f71c) to head (7ea9388).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
crates/prek/src/config.rs	87.50%	1 Missing ⚠️
...src/hooks/pre_commit_hooks/file_contents_sorter.rs	99.07%	1 Missing ⚠️
crates/prek/src/hooks/pre_commit_hooks/mod.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1846      +/-   ##
==========================================
+ Coverage   91.85%   91.88%   +0.03%     
==========================================
  Files         103      104       +1     
  Lines       20788    20920     +132     
==========================================
+ Hits        19095    19223     +128     
- Misses       1693     1697       +4     

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