Import style GHC plugin

The plugin helps to unify imports style via compile warnings/errors

Tested with:

• 9.2.7
• 9.4.8
• 9.6.4
• 9.8.2

Usage

Yaml config

Enable plugin in your cabal file:

 build-depends: ..., import-style-plugin, ... ghc-options: -fplugin ImportStylePlugin.Yaml -fplugin-opt ImportStylePlugin.Yaml:<path-to-config> 

Write config:

qualificationStyle: Post | Pre | null bannedModules: # can be null Module.Name: severity: Error | Warning why: string with ban reason importRules: # can be null DataModuleName: severity: Error | Warning rules: - qualification: Required | Forbidden | null aliases: # Either `exactly`, so alias can't be omitted exactly: - Module.Alias - Alias # or just list, so alias can be omitted - Module.Alias - Alias # or null importedNames: # Either whitelist, so import should be # accompanied with explicit import list whitelist: - pattern (:|>) - type (+) - foo # or blacklist, so import should be # accompanied with explicit hiding list with all these names # or explicit import list shouldn't contain any of these names blacklist: - pattern (:|>) - type (+) - foo # or null 

Here is example:

qualificationStyle: Post bannedModules: # Forbids Data.Map at all Data.Map: severity: Error why: Use 'Data.Map.Strict' importRules: # Either # import Data.Text (Text) # or # import Data.Text qualified as Text Data.Text: severity: Warning rules: - qualification: Required aliases: exactly: - Text - qualification: Forbidden importedNames: whitelist: - Text 

Derived plugin

It can be useful if you have a lot of projects with one style. So you haven't to copy paste config but just use style as library

1. Create library package
2. Add to deps import-style-plugin
3. Create module YourPlugin.hs (or something like that, it's unimportant)
4. Put there

   module YourPlugin where import ImportStylePlugin.Derived qualified as Derived import ImportStylePlugin.Config as Cfg -- variable name `plugin` IS important -- Configure your style with Haskell types from `ImportStylePlugin.Config` plugin = Derived.plugin ImportsStyle { qualificationStyle = ... , bannedModules = ... , importRules = ... } 

5. Plug in

    build-depends: ..., your-import-style-plugin, ... ghc-options: -fplugin YourPlugin 

Tips

Custom warning

Since ghc-9.8 the plugin introduces custom warning x-import-style. So if you set -Werror but still want to style warnings be warnings use ghc option -Wwarn=x-import-style. You also can disable at all warnings with -Wno-x-import-style