!badge
!npm
!npm

eslint-plugin-fp-ts

A collection of ESLint rules for fp-ts

Installation

Assuming ESlint is installed locally in your
project:

``sh


npm

npm install --save-dev eslint-plugin-fp-ts

yarn

yarn add --dev eslint-plugin-fp-ts
`

Then enable the plugin in your eslint.config.mjs file

`js
import {defineConfig} from 'eslint/config'
import fptsPlugin from 'eslint-plugin-fp-ts'

export default defineConfig(
{
plugins: {
'fp-ts': fptsPlugin,
}
}
)
`

and enable the rules you want, for example

`js
export default defineConfig(
{
plugins: {
'fp-ts': fptsPlugin,
},

rules: {
"fp-ts/no-lib-imports": "error"
}
}
)
`

If you want to enable rules that require type information (see the table below),
then you will also need to add some extra info:

`js
export default defineConfig(
{
plugins: {
'fp-ts': fptsPlugin,
},

languageOptions: {
parserOptions: {
projectService: true,
tsconfigRootDir: import.meta.dirname
}
},

rules: {
"fp-ts/no-discarded-pure-expression": "error",
}
}
)
`

If your project is a multi-package monorepo, you can follow the instructions
here.

> ⚠️ Note that you will need to make the ESLint config file a .js file, due to
> the need of setting tsconfigRootDir to __dirname. This is necessary to
> make both editor integrations and the CLI work with the correct path. More
> info here: https://github.com/typescript-eslint/typescript-eslint/issues/251

List of supported rules

| Rule | Description | Fixable | Requires type-checking |
| -------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------ | :-----: | :--------------------: |
| fp-ts/no-lib-imports | Disallow imports from fp-ts/lib/ | 🔧 | |
| fp-ts/no-pipeable | Disallow imports from the pipeable module | 🔧 | |
| fp-ts/no-module-imports | Disallow imports from fp-ts modules | 🔧 | |
| fp-ts/no-redundant-flow | Remove redundant uses of flow | 🔧 | |
| fp-ts/prefer-traverse | Replace map + sequence with traverse | 💡 | |
| fp-ts/prefer-chain | Replace map + flatten with chain | 💡 | |
| fp-ts/prefer-bimap | Replace map + mapLeft with bimap | 💡 | |
| fp-ts/no-discarded-pure-expression | Disallow expressions returning pure data types (like Task or IO) in statement position | 💡 | 🦄 |

$3

🔧 = auto-fixable via --fix (or via the appropriate editor configuration)

💡 = provides in-editor suggestions that need to be applied manually

Configurations

$3

The plugin defines a recommended configuration with some reasonable defaults.

To use it, add it to the extends clause of your eslint.config.mjs file:

`js
export default defineConfig(
{
plugins: {
'fp-ts': fptsPlugin,
},

extends: ["plugin:fp-ts/recommended"]
}
)
`

The rules included in this configuration are:

- fp-ts/no-lib-imports
- fp-ts/no-pipeable

$3

We also provide a recommended-requiring-type-checking which includes
recommended rules which require type information.

This configuration needs to be included _in addition_ to the recommended one:

`js
export default defineConfig(
{
plugins: {
'fp-ts': fptsPlugin,
},

extends: [
"fp-ts/recommended",
"fp-ts/recommended-requiring-type-checking"
]
}
)
`

> 👉 You can read more about linting with type information, including
> performance considerations
> here

$3

The plugin also defines an all configuration which includes every available
rule.

To use it, add it to the extends clause of your eslint.config.mjs file:

`js
export default defineConfig(
{
plugins: {
'fp-ts': fptsPlugin,
},

extends: ["fp-ts/all",]
}
)
``