Allow disabling automatic uv installation

[j178]

Add PREK_UV_SOURCE=none to require an existing compatible uv and fail instead of installing it.

Refs #2699.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-09T07:09:38.846752Z	ba84050	New commits

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.15%. Comparing base (c0b9749) to head (ba84050).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2702      +/-   ##
==========================================
+ Coverage   94.10%   94.15%   +0.05%     
==========================================
  Files         141      142       +1     
  Lines       30066    30218     +152     
==========================================
+ Hits        28293    28453     +160     
+ Misses       1773     1765       -8     

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[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 04f42f5e79

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[Copilot]

🟡 Changes recommended

The new test currently depends on host uv availability and the env-parsing unit test should be updated to cover the added none branch.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Adds support for PREK_UV_SOURCE=none so users can disable prek’s automatic uv installation and instead require an already-available compatible uv (alongside the prek binary, on PATH, or already in prek’s tools cache).

Changes:

• Document PREK_UV_SOURCE=none behavior in the env var reference and Python language docs.
• Implement a none install source that fails with a clear error when no compatible uv is found.
• Add an integration test covering the none behavior.

File summaries

File	Description
docs/reference/environment-variables.md	Documents the new none option and clarifies how prek behaves when auto-install is disabled.
docs/languages.md	Adds a pointer telling users how to disable automatic uv installation for Python hooks.
crates/prek/tests/languages/python.rs	Adds an integration test for PREK_UV_SOURCE=none behavior.
crates/prek/src/languages/python/uv.rs	Implements InstallSource::None and parses PREK_UV_SOURCE=none; updates invalid-value warning text.

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 3
• Review effort level: Lite

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[prek-ci-bot]

📦 Cargo Bloat Comparison

.text size change: +0.00% (12.8 MiB → 12.8 MiB)

Expand for cargo-bloat output

Head Branch Results

File  .text     Size             Crate Name
0.1%   2.5% 332.0KiB        aws_lc_sys aws_lc_0_44_0_aes_gcm_encrypt_avx512
0.1%   2.5% 332.0KiB        aws_lc_sys aws_lc_0_44_0_aes_gcm_decrypt_avx512
0.0%   0.7%  96.5KiB              prek <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
0.0%   0.4%  50.1KiB              prek <<prek::config::hook::HookWire as serde_core::de::Deserialize>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map::<&mut <serde_saphyr::de::deserializer::YamlDeserializer as serde_core::de::Deserializer>::deserialize_map::MA>
0.0%   0.4%  48.7KiB annotate_snippets annotate_snippets::renderer::render::render
0.0%   0.4%  46.7KiB              prek prek::run::{closure#0}
0.0%   0.3%  43.9KiB              prek <<prek::config::Config as serde_core::de::Deserialize>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map::<&mut <serde_saphyr::de::deserializer::YamlDeserializer as serde_core::de::Deserializer>::deserialize_map::MA>
0.0%   0.3%  39.8KiB              prek <prek::cli::RunOptions as clap_builder::derive::Args>::augment_args
0.0%   0.3%  35.3KiB              prek prek::cli::run::run::run::{closure#0}
0.0%   0.2%  28.9KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  28.7KiB      serde_saphyr <granit_parser::scanner::Scanner<granit_parser::input::str::StrInput>>::fetch_more_tokens
0.0%   0.2%  28.2KiB      serde_saphyr <granit_parser::scanner::Scanner<granit_parser::input::str::StrInput>>::fetch_more_tokens
0.0%   0.2%  28.0KiB        aws_lc_sys aws_lc_0_44_0_edwards25519_scalarmuldouble_alt
0.0%   0.2%  27.5KiB        aws_lc_sys aws_lc_0_44_0_edwards25519_scalarmuldouble
0.0%   0.2%  27.3KiB              toml <toml::de::deserializer::value::ValueDeserializer as serde_core::de::Deserializer>::deserialize_any::<<prek::config::hook::HookWire as serde_core::de::Deserialize>::deserialize::__Visitor>
0.0%   0.2%  27.1KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  26.9KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
4.2%  87.1%  11.1MiB                   And 20471 smaller methods. Use -n N to show more.
4.8% 100.0%  12.8MiB                   .text section size, the file size is 264.3MiB

Base Branch Results

File  .text     Size             Crate Name
0.1%   2.5% 332.0KiB        aws_lc_sys aws_lc_0_44_0_aes_gcm_encrypt_avx512
0.1%   2.5% 332.0KiB        aws_lc_sys aws_lc_0_44_0_aes_gcm_decrypt_avx512
0.0%   0.7%  96.5KiB              prek <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
0.0%   0.4%  50.1KiB              prek <<prek::config::hook::HookWire as serde_core::de::Deserialize>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map::<&mut <serde_saphyr::de::deserializer::YamlDeserializer as serde_core::de::Deserializer>::deserialize_map::MA>
0.0%   0.4%  49.7KiB              prek prek::run::{closure#0}
0.0%   0.4%  48.7KiB annotate_snippets annotate_snippets::renderer::render::render
0.0%   0.3%  43.9KiB              prek <<prek::config::Config as serde_core::de::Deserialize>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map::<&mut <serde_saphyr::de::deserializer::YamlDeserializer as serde_core::de::Deserializer>::deserialize_map::MA>
0.0%   0.3%  40.4KiB              prek prek::cli::run::run::run::{closure#0}
0.0%   0.3%  40.3KiB              prek <prek::cli::RunOptions as clap_builder::derive::Args>::augment_args
0.0%   0.3%  32.7KiB              prek <prek::languages::rust::rust::Rust as prek::languages::LanguageBackend>::install::{closure#0}
0.0%   0.2%  28.7KiB      serde_saphyr <granit_parser::scanner::Scanner<granit_parser::input::str::StrInput>>::fetch_more_tokens
0.0%   0.2%  28.2KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  28.2KiB      serde_saphyr <granit_parser::scanner::Scanner<granit_parser::input::str::StrInput>>::fetch_more_tokens
0.0%   0.2%  28.0KiB        aws_lc_sys aws_lc_0_44_0_edwards25519_scalarmuldouble_alt
0.0%   0.2%  27.5KiB        aws_lc_sys aws_lc_0_44_0_edwards25519_scalarmuldouble
0.0%   0.2%  27.3KiB              toml <toml::de::deserializer::value::ValueDeserializer as serde_core::de::Deserializer>::deserialize_any::<<prek::config::hook::HookWire as serde_core::de::Deserialize>::deserialize::__Visitor>
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
0.0%   0.2%  27.0KiB              prek prek::archive::unpack::<fs_err::tokio::file::File, &std::path::PathBuf>::{closure#0}
4.2%  86.9%  11.1MiB                   And 20372 smaller methods. Use -n N to show more.
4.8% 100.0%  12.8MiB                   .text section size, the file size is 263.7MiB

[prek-ci-bot]

⚡️ Hyperfine Benchmarks

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

Environment

• OS: Linux 6.17.0-1022-azure
• CPU: 4 cores
• prek version: prek 0.5.2+18 (b4fe159 2026-09-09)
• Rust version: rustc 1.98.1 (48a229cea 2026-09-01)
• 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 ± 0.2	2.1	3.3	1.04 ± 0.08
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	9.3 ± 0.2	8.9	9.7	1.00 ± 0.03
prek-head list	9.3 ± 0.2	8.9	10.1	1.00

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

⏭️ Skipped: .pre-commit-config.yaml not found

prek sample-config

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base sample-config	2.5 ± 0.1	2.4	2.8	1.00
prek-head sample-config	2.6 ± 0.2	2.4	3.2	1.03 ± 0.07

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	41.4 ± 2.0	38.2	45.1	1.06 ± 0.06
prek-head run --all-files	39.1 ± 1.1	37.1	40.3	1.00

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

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --all-files	40.1 ± 1.4	37.8	42.8	1.00
prek-head run --all-files	40.1 ± 1.3	37.4	42.0	1.00 ± 0.05

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	39.9 ± 2.3	37.5	54.2	1.00
prek-head run --all-files	40.6 ± 1.3	36.8	43.6	1.02 ± 0.07

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	13.7 ± 0.5	12.7	14.9	1.01 ± 0.05
prek-head run trailing-whitespace --all-files	13.6 ± 0.4	13.0	14.4	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	11.9 ± 0.5	10.6	12.9	1.01 ± 0.06
prek-head run end-of-file-fixer --all-files	11.7 ± 0.5	10.8	12.7	1.00

prek run check-json --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-json --all-files	8.0 ± 0.3	7.4	8.8	1.00
prek-head run check-json --all-files	8.2 ± 0.5	7.4	9.6	1.03 ± 0.07

prek run check-yaml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-yaml --all-files	8.1 ± 0.4	7.7	9.4	1.04 ± 0.06
prek-head run check-yaml --all-files	7.8 ± 0.2	7.6	8.4	1.00

prek run check-toml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-toml --all-files	7.9 ± 0.3	7.3	8.4	1.00
prek-head run check-toml --all-files	7.9 ± 0.6	7.4	9.8	1.00 ± 0.08

prek run check-xml --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-xml --all-files	7.8 ± 0.3	7.3	8.5	1.00
prek-head run check-xml --all-files	7.8 ± 0.4	7.2	9.1	1.00 ± 0.06

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

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run detect-private-key --all-files	11.3 ± 0.6	10.0	13.0	1.00
prek-head run detect-private-key --all-files	12.0 ± 0.5	11.2	13.2	1.06 ± 0.07

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	13.9 ± 1.0	12.5	16.2	1.03 ± 0.10
prek-head run fix-byte-order-marker --all-files	13.5 ± 0.8	12.2	15.9	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	4.5 ± 0.0	4.5	4.6	1.00
prek-head install-hooks	4.6 ± 0.2	4.5	4.9	1.03 ± 0.04

prek install-hooks (warm - with cache)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base install-hooks	4.9 ± 0.1	4.8	5.0	1.03 ± 0.03
prek-head install-hooks	4.8 ± 0.1	4.7	4.9	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	24.7 ± 0.4	24.2	25.5	1.00
prek-head run	25.0 ± 0.8	24.0	27.3	1.01 ± 0.04

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

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run --files '*.json'	5.7 ± 0.2	5.3	6.1	1.01 ± 0.04
prek-head run --files '*.json'	5.6 ± 0.1	5.4	5.9	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	7.2 ± 0.2	6.9	7.5	1.01 ± 0.04
prek-head run --dry-run --all-files	7.1 ± 0.2	6.8	7.5	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	8.4 ± 0.2	8.2	9.0	1.00
prek-head run check-hooks-apply --all-files	8.7 ± 0.2	8.4	9.1	1.03 ± 0.04

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

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run check-useless-excludes --all-files	8.4 ± 0.2	8.1	8.8	1.00
prek-head run check-useless-excludes --all-files	8.5 ± 0.2	8.2	9.2	1.00 ± 0.03

prek run identity --all-files

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
prek-base run identity --all-files	7.7 ± 1.6	7.1	13.5	1.06 ± 0.22
prek-head run identity --all-files	7.2 ± 0.1	7.1	7.3	1.00

[Copilot]

🟢 Approval recommended

The implementation and tests appear correct and low risk; the only feedback is a minor user-facing error-message clarity improvement.

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 1
• Review effort level: Lite