Registry / testing / eslint-plugin-fp-ts

eslint-plugin-fp-ts

library0.5.0jsnpmunverified

An ESLint plugin providing fp-ts-specific lint rules, including auto-fixable rules to detect deprecated imports (no-lib-imports, no-pipeable, no-module-imports) and to reduce redundant functional patterns (no-redundant-flow, prefer-traverse, prefer-chain, prefer-bimap), plus a rule to catch discarded pure expressions (no-discarded-pure-expression). Current stable version v0.5.0 requires ESLint ^9.0 and ships TypeScript definitions. The plugin has migrated to the new flat config format and now only supports ESLint v9, dropping support for v8. It relies on typescript-eslint for rules that need type checking.

testing

npm install eslint-plugin-fp-ts

github ↗package ↗

INSTALL

IMPORT

SIG · ESLINT-PLUGIN-FP-T

eslint-plugin-fp-ts

testingjavascriptv0.5.0

Install

—

Import

—

Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

default

✓ import fptsPlugin from 'eslint-plugin-fp-ts'

✗ const fptsPlugin = require('eslint-plugin-fp-ts')

The plugin is ESM-only since v0.5.0; require() will fail. Must use import for flat config.

no-lib-imports

✓ import { noLibImports } from 'eslint-plugin-fp-ts/rules/no-lib-imports'

✗ import { 'no-lib-imports' } from 'eslint-plugin-fp-ts'

Individual rules can be imported from 'eslint-plugin-fp-ts/rules/<rule-name>', but the plugin object is the simplest approach.

defineConfig

✓ import { defineConfig } from 'eslint/config'

✗ import { defineConfig } from 'eslint'

defineConfig is exported from 'eslint/config' in ESLint v9, not from the main 'eslint' package.

types

✓ import type { Plugin } from 'eslint'

✗ import { Plugin } from 'eslint'

Type imports should use import type to avoid runtime side effects.

Flat config example enabling 'no-lib-imports', 'no-redundant-flow', and 'no-discarded-pure-expression' rules with parser options for type checking.

import { defineConfig } from 'eslint/config'; import fptsPlugin from 'eslint-plugin-fp-ts'; export default defineConfig({ plugins: { 'fp-ts': fptsPlugin, }, languageOptions: { parserOptions: { projectService: true, tsconfigRootDir: import.meta.dirname, }, }, rules: { 'fp-ts/no-lib-imports': 'error', 'fp-ts/no-redundant-flow': 'error', 'fp-ts/no-discarded-pure-expression': 'warn', }, });

Debug

Known issues

breakingPlugin v0.5.0 drops support for ESLint v8; only ESLint v9 flat config is supported.

fix

Upgrade ESLint to ^9.0 and migrate to flat config (eslint.config.mjs).

affects: >=0.5.0

breakingPlugin v0.4.0 migrated to ESLint v9 and dropped CommonJS support; require() will fail.

fix

Use ESM imports and flat config or downgrade to v0.3.x if using eslintrc and CJS.

affects: >=0.4.0 <0.5.0

breakingPlugin v0.3.0 upgraded to ESLint v8, dropping ESLint v7 support.

fix

Upgrade ESLint to ^8.0 or use v0.2.x for ESLint v7.

affects: >=0.3.0 <0.4.0

gotchaRules that require type-checking (e.g., no-discarded-pure-expression) will not work without configuring parserOptions.projectService or project.

fix

Set parserOptions.projectService: true (or project) and tsconfigRootDir in languageOptions.

affects: >=0.2.0

deprecatedImporting from 'fp-ts/lib/' is deprecated; use 'fp-ts/<module>' instead.

fix

Use rule 'fp-ts/no-lib-imports' to enforce the new import style.

affects: >=0.0.0

Errors

Common errors & fixes

Error [ERR_REQUIRE_ESM]: require() of ES Module

Using require() to load the plugin when the package is ESM-only.

fix

Use import syntax: import fptsPlugin from 'eslint-plugin-fp-ts';

Configuration for rule "fp-ts/no-discarded-pure-expression" is invalid: has no properties.

Missing parser options for type-checking rules.

fix

Add languageOptions.parserOptions.projectService: true to your flat config.

ESLint couldn't find the plugin "eslint-plugin-fp-ts".

Plugin not installed or incorrectly referenced in config.

fix

Ensure eslint-plugin-fp-ts is installed and imported as shown in the quickstart.

Upgrade

Version history

0.5.0latest on npm

Audit

Dependencies

eslintrequiredpeer dependency; plugin is a set of ESLint rules that must be used with ESLint v9 or later

@typescript-eslint/parseroptionalrequired for rules that need type information (e.g., no-discarded-pure-expression)

Agent activity

4 hits · last 30 days

node

Resources

githubhttps://github.com/buildo/eslint-plugin-fp-ts ↗

packagehttps://www.npmjs.com/package/eslint-plugin-fp-ts ↗