Make sure child output is drained in the PTY subprocess by j178 · Pull Request #1768 · j178/prek

j178 · 2026-03-10T05:17:33Z

This should also fix the two flaky tests, color and run_with_stdin_closed.

This should fixed the two flaky test, `color` and `run_with_stdin_closed`.

codecov · 2026-03-10T05:19:16Z

Codecov Report

❌ Patch coverage is 90.62500% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.67%. Comparing base (ec2c03f) to head (3740a7a).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
crates/prek/src/process.rs	90.62%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1768      +/-   ##
==========================================
- Coverage   91.71%   91.67%   -0.04%     
==========================================
  Files          98       98              
  Lines       19847    19879      +32     
==========================================
+ Hits        18203    18225      +22     
- Misses       1644     1654      +10

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Pull request overview

This PR adjusts Cmd’s PTY execution path to better capture trailing subprocess output after a fast exit, aiming to eliminate flakiness in tests that rely on color/TTY behavior.

Changes:

Refactors PTY output collection into pty_output_inner and adds a post-exit drain step.
Introduces drain_ready_pty to opportunistically read remaining bytes after child.wait().
Adds a non-Windows async unit test to validate trailing output capture for fast-exiting commands.

crates/prek/src/process.rs

prek-ci-bot · 2026-03-10T05:23:45Z

📦 Cargo Bloat Comparison

Binary size change: +0.40% (24.7 MiB → 24.8 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_38_0_aes_gcm_encrypt_avx512
 1.3%   2.7% 332.0KiB        aws_lc_sys aws_lc_0_38_0_aes_gcm_decrypt_avx512
 0.3%   0.6%  77.6KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.3%   0.6%  69.8KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.3%   0.6%  68.0KiB             prek? <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
 0.2%   0.4%  51.0KiB annotate_snippets annotate_snippets::renderer::render::render
 0.2%   0.4%  50.6KiB              prek prek::languages::<impl prek::config::Language>::install::{{closure}}
 0.2%   0.4%  46.9KiB              prek prek::run::{{closure}}
 0.2%   0.3%  41.7KiB              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_38_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_38_0_edwards25519_scalarmuldouble
 0.1%   0.2%  25.8KiB              prek prek::cli::try_repo::try_repo::{{closure}}
 0.1%   0.2%  24.9KiB             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%  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%  22.0KiB               std core::ptr::drop_in_place<prek::languages::<impl prek::config::Language>::install::{{closure}}>
 0.1%   0.2%  21.6KiB              prek prek::workspace::Project::init_hooks::{{closure}}
41.1%  86.0%  10.2MiB                   And 23292 smaller methods. Use -n N to show more.
47.8% 100.0%  11.8MiB                   .text section size, the file size is 24.8MiB

Base Branch Results

 File  .text     Size             Crate Name
 1.3%   2.7% 332.0KiB        aws_lc_sys aws_lc_0_38_0_aes_gcm_encrypt_avx512
 1.3%   2.7% 332.0KiB        aws_lc_sys aws_lc_0_38_0_aes_gcm_decrypt_avx512
 0.3%   0.6%  77.6KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.3%   0.6%  71.7KiB             prek? <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
 0.3%   0.6%  69.8KiB              prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.2%   0.4%  51.0KiB annotate_snippets annotate_snippets::renderer::render::render
 0.2%   0.4%  50.6KiB              prek prek::languages::<impl prek::config::Language>::install::{{closure}}
 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_38_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_38_0_edwards25519_scalarmuldouble
 0.1%   0.2%  25.8KiB              prek prek::cli::try_repo::try_repo::{{closure}}
 0.1%   0.2%  24.9KiB             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%  23.1KiB              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%  22.0KiB               std core::ptr::drop_in_place<prek::languages::<impl prek::config::Language>::install::{{closure}}>
 0.1%   0.2%  21.5KiB              prek prek::workspace::Project::init_hooks::{{closure}}
41.1%  85.9%  10.2MiB                   And 23253 smaller methods. Use -n N to show more.
47.8% 100.0%  11.8MiB                   .text section size, the file size is 24.7MiB

prek-ci-bot · 2026-03-10T05:23:45Z

⚡️ Hyperfine Performance

Environment

OS: Linux 6.14.0-1017-azure
CPU: 4 cores
prek version: prek 0.3.5+6 (f291d04 2026-03-10)
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`	2.3 ± 0.1	2.2	2.6	1.01 ± 0.05
`prek-head --version`	2.3 ± 0.1	2.2	2.6	1.00

`prek list`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base list`	8.8 ± 0.2	8.5	10.7	1.00 ± 0.03
`prek-head list`	8.8 ± 0.1	8.6	9.1	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`	3.1 ± 0.0	3.0	3.3	1.03 ± 0.02
`prek-head validate-config .pre-commit-config.yaml`	3.0 ± 0.0	2.9	3.2	1.00

`prek sample-config`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base sample-config`	2.6 ± 0.1	2.5	2.7	1.00
`prek-head sample-config`	2.6 ± 0.0	2.6	2.7	1.02 ± 0.02

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`	149.2 ± 2.3	147.1	155.0	1.00
`prek-head run --all-files`	149.3 ± 1.5	147.1	152.4	1.00 ± 0.02

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

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run --all-files`	148.2 ± 2.4	144.6	153.5	1.00
`prek-head run --all-files`	148.3 ± 2.0	144.8	154.2	1.00 ± 0.02

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`	148.8 ± 1.7	145.7	152.8	1.00
`prek-head run --all-files`	151.3 ± 18.4	144.5	276.9	1.02 ± 0.12

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`	21.4 ± 0.4	20.9	22.8	1.01 ± 0.03
`prek-head run trailing-whitespace --all-files`	21.2 ± 0.4	20.4	22.0	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`	28.0 ± 1.5	25.3	31.0	1.01 ± 0.08
`prek-head run end-of-file-fixer --all-files`	27.6 ± 1.7	25.1	30.9	1.00

`prek run check-json --all-files`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run check-json --all-files`	12.1 ± 0.5	11.5	13.1	1.01 ± 0.05
`prek-head run check-json --all-files`	12.0 ± 0.3	11.3	12.6	1.00

`prek run check-yaml --all-files`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run check-yaml --all-files`	11.8 ± 0.2	11.5	12.2	1.01 ± 0.02
`prek-head run check-yaml --all-files`	11.7 ± 0.1	11.4	12.0	1.00

`prek run check-toml --all-files`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run check-toml --all-files`	12.0 ± 0.3	11.4	12.5	1.00
`prek-head run check-toml --all-files`	12.0 ± 0.3	11.4	12.6	1.00 ± 0.03

`prek run check-xml --all-files`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run check-xml --all-files`	12.0 ± 0.3	11.6	12.6	1.00 ± 0.03
`prek-head run check-xml --all-files`	12.0 ± 0.3	11.6	12.8	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`	4.7 ± 0.1	4.7	4.8	1.01 ± 0.02
`prek-head install-hooks`	4.7 ± 0.1	4.7	4.8	1.00

`prek install-hooks (warm - with cache)`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base install-hooks`	4.7 ± 0.0	4.7	4.8	1.00
`prek-head install-hooks`	4.7 ± 0.1	4.7	4.8	1.00 ± 0.01

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`	18.4 ± 0.1	18.2	18.6	1.00 ± 0.01
`prek-head run`	18.3 ± 0.1	18.1	18.5	1.00

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

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run --files '*.json'`	7.3 ± 0.1	7.2	7.5	1.00 ± 0.01
`prek-head run --files '*.json'`	7.3 ± 0.1	7.2	7.5	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`	12.3 ± 0.1	12.0	12.4	1.00 ± 0.01
`prek-head run --dry-run --all-files`	12.2 ± 0.1	12.0	12.5	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`	13.1 ± 0.8	12.3	14.0	1.05 ± 0.06
`prek-head run check-hooks-apply --all-files`	12.5 ± 0.1	12.3	12.8	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`	12.3 ± 0.1	12.2	12.5	1.00
`prek-head run check-useless-excludes --all-files`	12.4 ± 0.1	12.2	12.5	1.00 ± 0.01

`prek run identity --all-files`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`prek-base run identity --all-files`	10.8 ± 0.1	10.7	11.0	1.00
`prek-head run identity --all-files`	11.0 ± 0.3	10.7	11.8	1.02 ± 0.03

Make sure child output is drained in the PTY subprocess

3740a7a

This should fixed the two flaky test, `color` and `run_with_stdin_closed`.

Copilot AI review requested due to automatic review settings March 10, 2026 05:17

j178 added the bug Something isn't working label Mar 10, 2026

Copilot started reviewing on behalf of j178 March 10, 2026 05:18 View session

Copilot AI reviewed Mar 10, 2026

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crates/prek/src/process.rs Show resolved Hide resolved

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j178 merged commit 06fe54a into master Mar 10, 2026
55 checks passed

j178 deleted the drain branch March 10, 2026 05:25

BrewTestBot mentioned this pull request Mar 16, 2026

prek 0.3.6 Homebrew/homebrew-core#272532

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Pull request overview

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prek-ci-bot bot commented Mar 10, 2026

📦 Cargo Bloat Comparison

Head Branch Results

Base Branch Results

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prek-ci-bot bot commented Mar 10, 2026

⚡️ Hyperfine Performance

prek --version

prek list

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

prek sample-config

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

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

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

prek run trailing-whitespace --all-files

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

prek run check-json --all-files

prek run check-yaml --all-files

prek run check-toml --all-files

prek run check-xml --all-files

prek install-hooks (cold - no cache)

prek install-hooks (warm - with cache)

prek run (staged files only)

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

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

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

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

prek run identity --all-files

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j178 commented Mar 10, 2026 •

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`prek --version`

`prek list`

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

`prek sample-config`

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

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

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

`prek run trailing-whitespace --all-files`

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

`prek run check-json --all-files`

`prek run check-yaml --all-files`

`prek run check-toml --all-files`

`prek run check-xml --all-files`

`prek install-hooks (cold - no cache)`

`prek install-hooks (warm - with cache)`

`prek run (staged files only)`

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

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

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

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

`prek run identity --all-files`