---

name: hackage-read-docs description: Retrieve documentation from Hackage. Use this Skill when you need a reference for Haskell packages, classes, or want to query package versions. (project)

Hackage Read Docs

A CLI tool to query Hackage package documentation with filtering and display options.

Instructions

1. use bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- <package_name> --list-versions to discover what package versions are there
2. then use bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- <package_name> --version <version> to discover the modules that are in the package
3. If the hackage tool isn't finding modules, then use web fetch to https://hackage.haskell.org/package/<package_name> to discover directly the modules
4. And follow up with one of:
   • bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- <package_name> --module --filter-functions --with-comments --version
   • bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- <package_name> --module --filter-types --with-comments --version
   • bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- <package_name> --module --filter-classes --with-comments --version

Quick Start

List all available versions

Copybazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- aeson --list-versions

Query a specific version (shows tree view)

Copybazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- aeson --version 2.2.3.0

Deep dive into a module

Copybazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- aeson --module Data.Aeson

Filter Options

Show only specific types of exports:

Copy# Show only functions
bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- aeson --module Data.Aeson --filter-functions

# Show only types
bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- aeson --module Data.Aeson --filter-types

# Show only type classes
bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- aeson --module Data.Aeson --filter-classes

# Combine filters (e.g., show functions and types, exclude classes)
bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- aeson --module Data.Aeson --filter-functions --filter-types

Documentation Display

Include Haddock documentation text alongside signatures:

Copy# Show functions with their documentation
bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- aeson --module Data.Aeson --filter-functions --with-comments

# Show types with their documentation
bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- aeson --module Data.Aeson --filter-types --with-comments

# Show type classes with their documentation
bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- aeson --module Data.Aeson --filter-classes --with-comments

Common Patterns

Research a specific function

Copy# Find a function and see its documentation
bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- aeson --module Data.Aeson --filter-functions --with-comments | grep -A 3 "decode"

Explore all types in a module

Copy# See all type definitions with documentation
bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- containers --module Data.Map --filter-types --with-comments

Find available type classes

Copy# List type classes with their documentation
bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- aeson --module Data.Aeson --filter-classes --with-comments

Workflow

1. Start with version listing: Always list versions first, pick the latest if unclear

   Copybazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- PACKAGE --list-versions
   

2. Query package tree: View the package structure and available modules

   Copybazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- PACKAGE --version X.Y.Z
   

3. Explore specific module: Deep dive into a module with filters as needed

   Copybazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- PACKAGE --module MODULE.NAME
   

4. Apply filters: Use --filter-* flags to focus on specific export types

5. Include documentation: Add --with-comments to see Haddock documentation

Available Flags

• --version, -v VERSION: Query specific package version
• --list-versions, -l: List all available versions
• --module, -m MODULE: Query specific module (e.g., Data.Aeson)
• --filter-functions: Show only exported functions
• --filter-types: Show only exported types
• --filter-classes: Show only exported type classes
• --with-comments: Include Haddock documentation text alongside signatures

Examples

Copy# Research the aeson package's FromJSON class
bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- aeson --module Data.Aeson --filter-classes --with-comments | grep -A 10 "FromJSON"

# Find all functions in Data.List
bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- base --module Data.List --filter-functions

# Explore container types with documentation
bazel run //haskell/app/hackage-doc-cli:hackage-doc-cli -- containers --module Data.Map --filter-types --with-comments

Notes

• Default behavior (no filters): Shows functions, types, and type classes
• Documentation is extracted from Haddock HTML pages
• Supports both PVP and Semantic Versioning formats
• Results are cached for performance (24h for metadata, 7d for versions)