Support `Haskell` language by fllesser · Pull Request #1484 · j178/prek

fllesser · 2026-01-27T10:36:10Z

resolve #1445

codecov · 2026-01-27T10:38:17Z

Codecov Report

❌ Patch coverage is 87.96296% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.97%. Comparing base (f3d26b6) to head (52bc32b).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
crates/prek/src/languages/haskell.rs	87.73%	13 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1484      +/-   ##
==========================================
- Coverage   91.99%   91.97%   -0.02%     
==========================================
  Files          87       88       +1     
  Lines       18268    18376     +108     
==========================================
+ Hits        16805    16902      +97     
- Misses       1463     1474      +11

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j178

Thanks! Overall looks good. I added a few comments, and we’ll need to update the docs/languages.md file.

crates/prek/src/languages/haskell.rs

crates/prek/src/languages/mod.rs

crates/prek/tests/languages/haskell.rs

prek-ci-bot · 2026-01-27T13:28:06Z

📦 Cargo Bloat Comparison

Binary size change: +0.44% (22.5 MiB → 22.6 MiB)

Expand for cargo-bloat output

Head Branch Results

 File  .text    Size           Crate Name
 0.3%   0.8% 71.2KiB           prek? <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
 0.3%   0.7% 63.4KiB            prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.3%   0.6% 58.7KiB            prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.2%   0.5% 46.0KiB            prek prek::languages::<impl prek::config::Language>::install::{{closure}}
 0.2%   0.5% 43.2KiB            prek prek::run::{{closure}}
 0.2%   0.5% 43.1KiB            prek prek::identify::by_extension::{{closure}}
 0.2%   0.4% 41.5KiB            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% 22.1KiB            prek prek::hooks::meta_hooks::MetaHooks::run::{{closure}}
 0.1%   0.2% 22.1KiB            prek prek::hooks::meta_hooks::MetaHooks::run::{{closure}}
 0.1%   0.2% 21.0KiB    clap_builder clap_builder::parser::parser::Parser::get_matches_with
 0.1%   0.2% 20.6KiB            prek prek::archive::unzip::{{closure}}
 0.1%   0.2% 20.0KiB cargo_metadata? <cargo_metadata::_::<impl serde_core::de::Deserialize for cargo_metadata::Package>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map
 0.1%   0.2% 19.5KiB            prek prek::cli::run::filter::collect_files_from_args::{{closure}}
 0.1%   0.2% 19.3KiB            prek <prek::languages::ruby::ruby::Ruby as prek::languages::LanguageImpl>::install::{{closure}}
 0.1%   0.2% 19.1KiB            prek prek::cli::run::filter::collect_files_from_args::{{closure}}
 0.1%   0.2% 19.0KiB             std core::ptr::drop_in_place<prek::languages::<impl prek::config::Language>::install::{{closure}}>
 0.1%   0.2% 18.6KiB            ring ring_core_0_17_14__x25519_ge_frombytes_vartime
 0.1%   0.2% 18.1KiB       [Unknown] fe_loose_invert
 0.1%   0.2% 18.1KiB      hyper_util hyper_util::client::legacy::client::Client<C,B>::send_request::{{closure}}
36.8%  91.5%  8.3MiB                 And 20080 smaller methods. Use -n N to show more.
40.2% 100.0%  9.1MiB                 .text section size, the file size is 22.6MiB

Base Branch Results

 File  .text    Size           Crate Name
 0.3%   0.8% 77.0KiB           prek? <prek::cli::Command as clap_builder::derive::Subcommand>::augment_subcommands
 0.3%   0.6% 59.1KiB            prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.2%   0.6% 56.6KiB            prek prek::languages::<impl prek::config::Language>::run::{{closure}}::{{closure}}
 0.2%   0.5% 43.2KiB            prek prek::run::{{closure}}
 0.2%   0.5% 43.1KiB            prek prek::identify::by_extension::{{closure}}
 0.2%   0.4% 41.5KiB            prek prek::cli::run::run::run::{{closure}}
 0.2%   0.4% 41.0KiB            prek prek::languages::<impl prek::config::Language>::install::{{closure}}
 0.1%   0.3% 32.0KiB           prek? <prek::cli::RunArgs as clap_builder::derive::Args>::augment_args
 0.1%   0.2% 21.7KiB            prek prek::hooks::meta_hooks::MetaHooks::run::{{closure}}
 0.1%   0.2% 21.7KiB            prek prek::hooks::meta_hooks::MetaHooks::run::{{closure}}
 0.1%   0.2% 21.0KiB    clap_builder clap_builder::parser::parser::Parser::get_matches_with
 0.1%   0.2% 20.8KiB            prek prek::archive::unzip::{{closure}}
 0.1%   0.2% 20.0KiB cargo_metadata? <cargo_metadata::_::<impl serde_core::de::Deserialize for cargo_metadata::Package>::deserialize::__Visitor as serde_core::de::Visitor>::visit_map
 0.1%   0.2% 19.5KiB            prek prek::cli::run::filter::collect_files_from_args::{{closure}}
 0.1%   0.2% 19.3KiB            prek <prek::languages::ruby::ruby::Ruby as prek::languages::LanguageImpl>::install::{{closure}}
 0.1%   0.2% 19.1KiB            prek prek::cli::run::filter::collect_files_from_args::{{closure}}
 0.1%   0.2% 18.6KiB            ring ring_core_0_17_14__x25519_ge_frombytes_vartime
 0.1%   0.2% 18.2KiB             std core::ptr::drop_in_place<prek::languages::<impl prek::config::Language>::install::{{closure}}>
 0.1%   0.2% 18.1KiB       [Unknown] fe_loose_invert
 0.1%   0.2% 18.1KiB      hyper_util hyper_util::client::legacy::client::Client<C,B>::send_request::{{closure}}
36.8%  91.6%  8.3MiB                 And 20097 smaller methods. Use -n N to show more.
40.2% 100.0%  9.1MiB                 .text section size, the file size is 22.5MiB

fllesser · 2026-01-28T05:30:54Z

cabal update and cabal install seem to be very slow.

To mitigate the race condition issue with cabal update, I switched to serialized testing, which now takes over 180 seconds in CI. Are there any solutions to this?

crates/prek/src/languages/haskell.rs

j178 · 2026-01-28T09:58:14Z

Can we skip cabal update in CI via a special env var (e.g PREK_INTERNAL__SKIP_CABAL_UPDATE)?

fllesser · 2026-01-28T10:34:27Z

Ok

Add remote hook test Add `haskell-setup` ci tweak tweak tweak clippy fix tweak tweak fix unimplemented test tweak

tweak

.github/workflows/ci.yml

fllesser · 2026-01-29T16:48:45Z

The haskell-actions/setup is excessively slow，especially macOS

# Conflicts: # .github/workflows/ci.yml

Copilot

Pull request overview

This pull request adds support for the Haskell language to prek, resolving issue #1445. The implementation installs Haskell hooks via Cabal and runs configured entries using the system's cabal and ghc installations.

Changes:

Implemented Haskell language support with cabal v2-install for dependency management
Added comprehensive test coverage including local hooks, additional dependencies, and remote hooks
Updated CI/CD pipeline to run Haskell tests with GHC 9.8.2 and Cabal 3.16.1.0

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
`docs/languages.md`	Updated documentation to mark Haskell as supported with usage instructions
`crates/prek/src/languages/haskell.rs`	New implementation of Haskell language support using Cabal for installation and execution
`crates/prek/src/languages/mod.rs`	Integrated Haskell language into the language registry
`crates/prek/tests/languages/haskell.rs`	Added comprehensive tests for local hooks, additional dependencies, and remote hooks
`crates/prek/tests/languages/main.rs`	Added haskell module to test suite
`crates/prek/tests/languages/unimplemented.rs`	Updated to use R language as example of unimplemented language
`crates/prek-consts/src/env_vars.rs`	Added `PREK_INTERNAL__SKIP_CABAL_UPDATE` environment variable for testing
`.github/workflows/ci.yml`	Added Haskell to CI matrix with GHC/Cabal installation and caching on macOS
`.config/nextest.toml`	Added lang-haskell test profile configuration

crates/prek/src/languages/haskell.rs

.github/workflows/ci.yml

crates/prek/src/languages/haskell.rs

.github/workflows/ci.yml

crates/prek/tests/languages/haskell.rs

crates/prek/src/languages/haskell.rs

j178 · 2026-01-31T12:28:35Z

Thank you!

j178 reviewed Jan 27, 2026

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crates/prek/src/languages/haskell.rs Show resolved Hide resolved

crates/prek/src/languages/mod.rs Outdated Show resolved Hide resolved

crates/prek/tests/languages/haskell.rs Outdated Show resolved Hide resolved

j178 added the enhancement New feature or request label Jan 28, 2026

fllesser marked this pull request as draft January 28, 2026 04:21

j178 reviewed Jan 28, 2026

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crates/prek/src/languages/haskell.rs Outdated Show resolved Hide resolved

fllesser marked this pull request as ready for review January 28, 2026 11:35

fllesser added 8 commits January 28, 2026 19:37

Support Haskell language

bcf2e50

Add remote hook test Add `haskell-setup` ci tweak tweak tweak clippy fix tweak tweak fix unimplemented test tweak

tweak

dcb107c

fix pkgs

3ec92a7

tweak

Use OnceCell to wrap the cabal update

d9ca2cf

Add health_check test

b1b9733

query haskell info

f709e92

Remove unnecessary health check and skip cabal update in CI

e39f6d2

tweak

786b3f2

fllesser force-pushed the haskell branch from f24c5cf to 786b3f2 Compare January 28, 2026 11:37

fllesser added 2 commits January 29, 2026 23:50

tweak

409a1da

try to use actions/setup-haskell on macOS

95235d8

github-advanced-security bot found potential problems Jan 29, 2026

View reviewed changes

.github/workflows/ci.yml Fixed Show fixed Hide fixed

fllesser added 2 commits January 30, 2026 00:27

tweak

c23c2ce

tweak

1d3b83d

fllesser added 5 commits January 30, 2026 00:57

ghc 9.4.8

8f61fd5

revert

e4c1036

tweak

732a55d

cache haskell and use ghc 9.8.2

e393940

tweak

18e89a9

fllesser added 7 commits January 30, 2026 13:44

tweak cache key

e2afe86

only cache on macOS

e4f999e

tweak

1c1894f

tweak

4261d3f

tweak

565f95d

tweak

90136b5

cache ghc only on macOS

affbd79

fllesser marked this pull request as draft January 30, 2026 07:15

Tweaks

31b226f

j178 force-pushed the haskell branch from 43b8c73 to 31b226f Compare January 30, 2026 19:35

Merge branch 'master' into haskell

cdfd509

# Conflicts: # .github/workflows/ci.yml

j178 marked this pull request as ready for review January 31, 2026 12:06

Copilot AI review requested due to automatic review settings January 31, 2026 12:06

Copilot started reviewing on behalf of j178 January 31, 2026 12:07 View session

Cache GHC

2d36ecc

j178 force-pushed the haskell branch from fe44106 to 2d36ecc Compare January 31, 2026 12:09

Copilot AI reviewed Jan 31, 2026

View reviewed changes

Fixes

52bc32b

j178 merged commit d12e0be into j178:master Jan 31, 2026
45 checks passed

BrewTestBot mentioned this pull request Jan 31, 2026

prek 0.3.1 Homebrew/homebrew-core#265311

Merged

fllesser deleted the haskell branch January 31, 2026 16:04

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📦 Cargo Bloat Comparison

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fllesser commented Jan 27, 2026 •

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