migrating-from-tslint.md

Migrating from TSLint

TSLint is now deprecate. This guide is intended to help those who are using tslint-immutable to migrate their settings and projects to use eslint-plugin-functional.

Configuration File

The ESLint version of tslint.json (the configuration file) is .eslintrc. See ESLint's docs for more information on this file.

Out of the box, ESLint does not understand TypeScript. To get ESLint to understand it we need to change the default parser to one that understands it. This is where @typescript-eslint comes in. In the config file, we can specify the parser to be used with the "parser" key. Any extra parser configuration can then be specified under the "parserOptions" key. In order for the parser to have access to type information, it needs access to your tsconfig.json; you'll need to specify this under "parserOptions" -> "project".

Example config

{
  "root": true,
  "parser": "@typescript-eslint/parser",
  "parserOptions": {
    "ecmaVersion": 10,
    "project": "./tsconfig.json",
    "sourceType": "module"
  },
  "plugins": [
    "functional"
  ],
  "env": {
    "es6": true
  },
  "extends": [
    "plugin:functional/recommended"
  ],
  "rules": {
    // These rules will be applied to all linted file.
  },
  "overrides": [
    {
      "files": ["*.ts", "*.tsx"],
      "rules": {
        // These rules will only be applied to ts file.
      }
    }
  ]
}

Rules

Below is a table mapping the eslint-plugin-functional rules to their tslint-immutable equivalents.

eslint-plugin-functional Rule	Equivalent tslint-immutable Rules
functional/prefer-readonly-type	readonly-keyword & readonly-array
functional/no-let	no-let
functional/immutable-data	no-object-mutation, no-array-mutation & no-delete
functional/no-method-signature	no-method-signature
functional/no-this-expression	no-this
functional/no-class	no-class
functional/no-mixed-type	no-mixed-interface
functional/no-expression-statement	no-expression-statement
functional/no-conditional-statement	no-if-statement
functional/no-loop-statement	no-loop-statement
functional/no-return-void	-
functional/no-throw-statement	no-throw
functional/no-try-statement	no-try
functional/no-promise-reject	no-reject
functional/functional-parameters	-