haskell-tasuke

Use bracket or with-style functions to guarantee resource cleanup even on exceptions instead of separate do blocks. Use when writing or reviewing Haskell code that acquires and releases resources.

Update Cabal project index-state to the latest timestamp. Use when it needs to bump the cabal index-state.

Use cabal with --disable-optimization for development builds and tests, and add --enable-tests to avoid rebuilds. Use when running or suggesting cabal build or test commands in Haskell development.

Do not throw exceptions from pure code with error or throw, give exceptions structured types, and never silently swallow errors in IO. Use when writing or reviewing Haskell error handling, exceptions, or IO code.

Explicitly enumerate Haskell module exports instead of exporting everything implicitly, and use re-export sparingly. Use when writing or reviewing Haskell module export lists.

Do not discard a function's final value with return (), pure (), or void; adjust the type to return the value and let the caller discard it when unneeded. Use when writing or reviewing Haskell functions that return unit or discard results.

himari is ncaq's rio-like custom Haskell Prelude. Import it with a single `import Himari`, never `import Himari.Prelude` or other submodules directly. Use when writing or reviewing Haskell code in a project that depends on the himari package.

Prefer MonadIO and MonadUnliftIO type classes over using IO directly, and avoid redundant liftIO. Use when writing or reviewing Haskell IO actions, monad transformers, or type class abstractions.

Haskell language extension and language edition (GHC2024/GHC2021) selection policy. Use when configuring or reviewing Haskell language extensions, cabal default-extensions, or default-language.

Use the lens library, generating accessors with makeFieldsId for NoFieldSelectors records, export accessors together with their type classes, and prefer lens or OverloadedRecordDot over pattern matching. Use when writing or reviewing Haskell code that uses lens, records, or field access.

Avoid mutable variables like IORef, STRef, and ST in Haskell and prefer immutable records. Use STM variables such as TVar for thread communication. Use when writing or reviewing Haskell code that uses mutable state or concurrency.

Avoid partial functions such as head, fromJust, read, and (!!) in Haskell. Prefer total functions, Maybe-returning variants, and other safe alternatives. Use when writing or reviewing Haskell code that accesses lists, parses strings, or handles Maybe.

Prefer Text over String for text data, and use ByteString for binary or non-Unicode data. Use when writing or reviewing Haskell code that handles strings, text, or byte data.

Distinguish mkName and newName in Template Haskell. Use mkName to capture existing names and newName for fresh non-colliding names. Use when writing or reviewing Template Haskell code that generates names.

When testing Either values, compare the value directly with shouldBe instead of checking isLeft, so test failures show the actual value. Use when writing or reviewing Haskell test code that asserts on Either or similar values.

Name Haskell test modules after the module under test with a Spec suffix in the same namespace. Use when writing or reviewing Haskell test module names or test file organization.

Avoid overusing threadDelay because time-dependent code is unstable and unportable. Prefer synchronization variables like TMVar or retry combinators. Use when writing or reviewing Haskell code that delays threads, waits, or polls.

Forbid unsafe Haskell functions such as unsafePerformIO, unsafeCoerce, and other unsafe-prefixed functions. Use when writing or reviewing Haskell code that uses any unsafe-prefixed function.

Do not disable GHC or hlint warnings. Suppress them only per module with OPTIONS_GHC or annotations for justified exceptions. Use when writing or reviewing Haskell code, cabal files, or hlint configuration that disables warnings.