haskell-lsp-plugin

Haskell Claude Tools

An opinionated, third-party Claude Code plugin marketplace for Haskell development. It bundles a Language Server plugin, a local documentation/source reader, on-save formatters for sources and cabal files, and an orchestrating "super-skill" that ties them together into one cabal-native workflow.

Marketplace name: konn-haskell-claude-tools.

What's inside

Plugin	Provides	Invoke
haskell-lsp-plugin	Haskell Language Server (HLS) — diagnostics, hover/types, go-to-definition, find-references, rename	LSP tools (automatic once installed)
haskell-haddock-skill	Read local Haddock HTML docs and package source for your cabal dependencies; falls back to Hackage for the rest	/haddock <package> [module]
haskell-format-skill	Format .hs/.lhs/.hsig sources with the project's formatter (fourmolu/ormolu/stylish-haskell); on-save hook formats automatically	/haskell-format
haskell-cabal-gild-skill	Format .cabal/cabal.project files with cabal-gild; on-save hook formats automatically and refreshes discover module lists	/haskell-cabal-gild
haskell-skill	Orchestrating super-skill for cabal nix-style development; drives the LSP, Haddock, Hoogle, and the formatters	/haskell (or any Haskell dev task)

The Hoogle search skills (/hoogle:search, /hoogle:remote) come from the external claude-hoogle marketplace, which haskell-skill declares as a dependency.

Requirements

• Claude Code with plugin support.
• haskell-language-server — haskell-language-server-wrapper must be on your PATH (e.g. installed via GHCup) for haskell-lsp-plugin.
• cabal ≥ 3.12 and GHC, used in nix-style (cabal.project) mode. haskell-haddock-skill relies on cabal path and dist-newstyle/cache/plan.json.
• For the formatting plugins (used by their on-save hooks): cabal-gild for haskell-cabal-gild-skill, and one of fourmolu / ormolu / stylish-haskell for haskell-format-skill. If a tool isn't on your PATH, its hook quietly does nothing.
• The claude-hoogle marketplace, for the Hoogle skills (see Installation).

Installation

Add this marketplace, then install the plugin(s) you want:

/plugin marketplace add https://github.com/konn/haskell-claude-marketplace
/plugin install haskell-skill@konn-haskell-claude-tools

haskell-skill depends on the hoogle plugin from another marketplace. Because Claude Code does not silently pull plugins across marketplaces, add claude-hoogle first so the dependency can resolve:

/plugin marketplace add https://github.com/m4dc4p/claude-hoogle
/plugin install haskell-skill@konn-haskell-claude-tools

Install individual pieces instead if you prefer:

/plugin install haskell-lsp-plugin@konn-haskell-claude-tools
/plugin install haskell-haddock-skill@konn-haskell-claude-tools
/plugin install haskell-format-skill@konn-haskell-claude-tools
/plugin install haskell-cabal-gild-skill@konn-haskell-claude-tools

Using the tools

/haskell — development workflow

The entry point for Haskell work. It treats cabal.project as the source of truth, works package-by-package, formats before compiling (via /haskell-format and /haskell-cabal-gild), prefers the LSP over a full cabal build for quick feedback, and prefers local documentation over remote lookups. It delegates to /haddock and the Hoogle skills for API discovery.

/haddock — local docs & source

Reads documentation and source for your project's dependencies from cabal's local store and repo-cache, so you avoid hitting Hackage. One-time setup per project:

cabal configure --enable-documentation   # ensures `documentation: True`
cabal build all                           # materialises docs/source for dependencies

It then resolves each dependency through cabal path and the UnitId recorded in dist-newstyle/cache/plan.json (cabal abbreviates package names in the store, so paths cannot be guessed from the package name). Packages outside the dependency set fall back to Hackage.

/haskell-format — format sources

Formats .hs/.lhs/.hsig with the project's formatter, chosen by config (fourmolu.yaml / .fourmolu.yaml → fourmolu, .stylish-haskell.yaml → stylish-haskell) or the first of fourmolu → ormolu → stylish-haskell found on PATH. An on-save hook runs it automatically whenever such a file is written, so code stays formatted without an explicit call.