.eslintrc

{
  "extends": [
    "eslint:recommended",
    "plugin:@typescript-eslint/recommended",
    "plugin:jsdoc/recommended-typescript-error",
    "plugin:jest/recommended",
    "plugin:prettier/recommended" // MUST BE LAST!
  ],
  "plugins": [
    "@typescript-eslint",
    "simple-import-sort",
    "jest",
    "unicorn"
  ],

  "parser": "@typescript-eslint/parser",
  "parserOptions": {
    "project": "./tsconfig.json",
    "sourceType": "module"
  },
  "ignorePatterns": ["dist/**"],

  "env": {
    "jest/globals": true
  },

  "rules": {
    // ***** Files *****
    "unicorn/no-empty-file": "error",
    "unicorn/filename-case": ["error", {
      "case": "camelCase"
    }],

    // ***** Imports *****
    "unicorn/prefer-node-protocol": "error",
    "simple-import-sort/exports": "error",
    "simple-import-sort/imports": "error",

    // ***** JSDoc *****
    "jsdoc/require-jsdoc": ["error", {
      // Require on public parts of classes
      "checkConstructors": false,
      "contexts": [
        "ClassDeclaration",
        // TODO(cemmer): require private methods as well
        "MethodDefinition[accessibility!=private][key.name!=/^(get|set|with)[A-Z][a-zA-Z]+/]"
      ]
    }],
    "jsdoc/require-param": "off",
    "jsdoc/require-returns": "off",
    "jsdoc/no-blank-blocks": "error",

    // ***** Types *****
    "unicorn/no-null": "error",

    // ***** Promises *****
    // Disallow awaiting a value that is not a Thenable.
    "@typescript-eslint/await-thenable": "error",
    // Disallow async functions which have no `await` expression.
    "@typescript-eslint/require-await": "error",
    // Enforce consistent returning of awaited values.
    "@typescript-eslint/return-await": "error",
    // Require any function or method that returns a Promise to be marked async.
    "@typescript-eslint/promise-function-async": ["error"],

    // ***** Classes *****
    "@typescript-eslint/prefer-readonly": "error",
    "unicorn/new-for-builtins": "error",
    "unicorn/no-static-only-class": "error",

    // ***** Functions *****
    // Require explicit return types on functions and class methods.
    "@typescript-eslint/explicit-function-return-type": "error",
    "unicorn/prefer-default-parameters": "error",

    // ***** Errors *****
    "unicorn/catch-error-name": "error",
    "unicorn/prefer-optional-catch-binding": "error",

    // ***** Operands *****
    "@typescript-eslint/prefer-nullish-coalescing": "error",

    // ***** Conditionals *****
    // Don't allow unnecessary conditional checks, such as when a value is always true, which can also help catch cases
    // such as accidentally checking `if([]){}` vs. `if([].length){}`
    "@typescript-eslint/strict-boolean-expressions": ["error", {
      "allowAny": true,
      "allowNullableBoolean": true,
      "allowNullableString": true
    }],
    // Don't allow truthy or falsey conditionals on array lengths
    "unicorn/explicit-length-check": "error",

    // ***** Loops *****
    "unicorn/no-for-loop": "error",

    // ***** Objects *****
    "@typescript-eslint/no-unused-vars": ["error", {
      // Allow the use of destructuring to remove keys from an object
      "ignoreRestSiblings": true
    }],

    // ***** Arrays *****
    "no-restricted-syntax": ["error", {
      "selector": "CallExpression[callee.property.name='push'] > SpreadElement",
      "message": "Array#push(...Array) can cause 'call stack size exceeded' runtime errors when pushing many values, prefer 'Array = [...Array, ...Array]'"
    }],
    "unicorn/no-new-array": "error",
    // TypeScript doesn't do a good job of reporting indexed values as potentially undefined, such as `[1,2,3][999]`
    "unicorn/prefer-at": "error",
    // Try to enforce early terminations of loops, rather than statements such as `.find(x=>x)[0]`
    "unicorn/prefer-array-find": ["error", {"checkFromLast": false}],
    "unicorn/prefer-array-flat": "error",
    "unicorn/prefer-array-flat-map": "error",
    "unicorn/prefer-includes": "error",
    "unicorn/prefer-object-from-entries": "error",

    // ***** Numbers *****
    "unicorn/no-zero-fractions": "error",
    "unicorn/numeric-separators-style": "error",
    "unicorn/prefer-number-properties": "error",

    // ***** Strings *****
    "unicorn/prefer-code-point": "error",

    // ********** Recommended Overrides **********

    // ***** eslint:recommended *****
    // Referencing ASCII characters <32 is entirely legitimate
    "no-control-regex": "off",

    // ***** plugin:@typescript-eslint/recommended *****
    // There are a few places where this needs to be allowed, but only a few, so warn on them
    "@typescript-eslint/no-floating-promises": "warn",
    // There are a few places where this needs to be allowed, but only a few, so warn on them
    "@typescript-eslint/no-unused-expressions": "warn",

    // ***** airbnb-base, airbnb-typescript/base *****
    "no-await-in-loop": "off",
    "no-bitwise": "off",

    // ***** plugin:jest/recommended *****
    // A lot of test files define their own expect functions
    "jest/expect-expect": "off"
  },

  "overrides": [
    {
      "files": [
        "test/**/*.ts",
        // TODO(cemmer)
        "src/polyfill/**/*.ts",
        "src/types/files/**/*.ts",
        "src/types/patches/**/*.ts"
      ],
      "rules": {
        "jsdoc/require-jsdoc": "off"
      }
    }
  ]
}