index.js

'use strict';
module.exports = {
	parser: require.resolve('@typescript-eslint/parser'),
	parserOptions: {
		warnOnUnsupportedTypeScriptVersion: false,
		sourceType: 'module',
		jsx: true,
		project: 'tsconfig.json'
	},
	plugins: [
		'@typescript-eslint'
	],
	settings: {
		'import/resolver': {
			node: {
				extensions: [
					'.js',
					'.jsx',
					'.ts',
					'.tsx'
				]
			}
		},
		'import/parsers': {
			'@typescript-eslint/parser': [
				'.ts',
				'.tsx'
			]
		}
	},
	rules: {
		'@typescript-eslint/adjacent-overload-signatures': 'error',
		'@typescript-eslint/array-type': [
			'error',
			{
				default: 'array-simple'
			}
		],
		'@typescript-eslint/await-thenable': 'error',
		'@typescript-eslint/ban-types': [
			'error',
			{
				types: {
					String: {
						message: 'Use `string` instead.',
						fixWith: 'string'
					},
					Number: {
						message: 'Use `number` instead.',
						fixWith: 'number'
					},
					Boolean: {
						message: 'Use `boolean` instead.',
						fixWith: 'boolean'
					},
					Symbol: {
						message: 'Use `symbol` instead.',
						fixWith: 'symbol'
					},
					Object: {
						message: 'The `Object` type is mostly the same as `unknown`. You probably want `Record<string, unknown>` instead. See https://github.com/typescript-eslint/typescript-eslint/pull/848',
						fixWith: 'Record<string, unknown>'
					},
					'{}': {
						message: 'The `{}` type is mostly the same as `unknown`. You probably want `Record<string, unknown>` instead.',
						fixWith: 'Record<string, unknown>'
					},
					object: {
						message: 'The `object` type is hard to use. Use `Record<string, unknown>` instead. See: https://github.com/typescript-eslint/typescript-eslint/pull/848',
						fixWith: 'Record<string, unknown>'
					},
					Function: 'Use a specific function type instead, like `() => void`.',

					// TODO: Enforce `undefined` over `null` here too?

					Omit: 'Prefer the `Except` type in the `type-fest` package instead as it\'s stricter.',
				}
			}
		],
		'brace-style': 'off',
		'@typescript-eslint/brace-style': [
			'error',
			'1tbs',
			{
				allowSingleLine: false
			}
		],
		'comma-spacing': 'off',
		'@typescript-eslint/comma-spacing': [
			'error',
			{
				before: false,
				after: true
			}
		],
		'default-param-last': 'off',
		'@typescript-eslint/default-param-last': 'error',
		'@typescript-eslint/consistent-type-assertions': [
			'error',
			{
				assertionStyle: 'as',
				objectLiteralTypeAssertions: 'allow-as-parameter'
			}
		],

		// Disabled because it's not fully usable yet:
		// https://github.com/typescript-eslint/typescript-eslint/issues/142
		// '@typescript-eslint/consistent-type-definitions': [
		// 	'error',
		// 	'type'
		// ],

		'@typescript-eslint/explicit-function-return-type': [
			'error',
			{
				allowExpressions: true,
				allowTypedFunctionExpressions: true
			}
		],

		// Disabled for now as it has too many false-positives.
		// '@typescript-eslint/explicit-module-boundary-types': [
		// 	'error',
		// 	{
		// 		allowTypedFunctionExpressions: true,
		// 		allowHigherOrderFunctions: true,
		// 		allowDirectConstAssertionInArrowFunctions: true
		// 	}
		// ],

		'func-call-spacing': 'off',
		'@typescript-eslint/func-call-spacing': [
			'error',
			'never'
		],
		indent: 'off',
		'@typescript-eslint/indent': [
			'error',
			'tab',
			{
				SwitchCase: 1
			}
		],
		'@typescript-eslint/member-delimiter-style': [
			'error',
			{
				multiline: {
					delimiter: 'semi',
					requireLast: true
				},
				singleline: {
					delimiter: 'semi',
					requireLast: false
				}
			}
		],
		'@typescript-eslint/member-ordering': 'error',
		// We use `@typescript-eslint/naming-convention` in favor of `camelcase`.
		camelcase: 'off',
		// DON't push this until typescript-eslint 2.17 is out. And test it on Got and RG.
		// TODO: Prevent `_` prefix on private fields when TypeScript 3.8 is out.
		'@typescript-eslint/naming-convention': [
			'error',
			{
				selector: 'default',
				format: [
					'strictCamelCase'
				],
				leadingUnderscore: 'allow',
				trailingUnderscore: 'allow'
			},
			{
				selector: 'typeLike',
				format: [
					'StrictPascalCase'
				]
			},
			{
				selector: 'variable',
				types: [
					'boolean'
				],
				format: [
					'StrictPascalCase'
				],
				prefix: [
					'is',
					'has',
					'can',
					'should',
					'will',
					'did'
				]
			},
			{
				// Interface name should not be prefixed with `I`.
				selector: 'interface',
				filter: /^(?!I)[A-Z]/.source,
				format: [
					'StrictPascalCase'
				]
			},
			{
				// Type parameter name should either be `T` or a descriptive name.
				selector: 'typeParameter',
				filter: /^T$|^[A-Z][a-zA-Z]+$/.source,
				format: [
					'StrictPascalCase'
				]
			}
		],
		'no-array-constructor': 'off',
		'@typescript-eslint/no-array-constructor': 'error',
		'@typescript-eslint/no-dynamic-delete': 'error',
		'no-empty-function': 'off',
		'@typescript-eslint/no-empty-function': 'error',
		'@typescript-eslint/no-empty-interface': [
			'error',
			{
				allowSingleExtends: true
			}
		],

		// TODO: Try to enable this again in 2021.
		// Disabled for now. This is a great rule. It's just that TypeScript is not good enough yet to not use `any` in many places.
		// For example: https://github.com/sindresorhus/refined-github/pull/2391#discussion_r318995182
		// '@typescript-eslint/no-explicit-any': [
		// 	'error',
		// 	{
		// 		fixToUnknown: true,
		// 		ignoreRestArgs: true
		// 	}
		// ],

		'@typescript-eslint/no-extra-non-null-assertion': 'error',

		// Disabled because it's buggy. It transforms `...(personalToken ? {Authorization: `token ${personalToken}`} : {})` into `...personalToken ? {Authorization: `token ${personalToken}`} : {}` which is not valid.
		// TODO: Report this issue.
		'no-extra-parens': 'off',
		// '@typescript-eslint/no-extra-parens': [
		// 	'error',
		// 	'all',
		// 	{
		// 		conditionalAssign: false,
		// 		nestedBinaryExpressions: false,
		// 		ignoreJSX: 'multi-line'
		// 	}
		// ],

		'no-extra-semi': 'off',
		'@typescript-eslint/no-extra-semi': 'error',
		'@typescript-eslint/no-extraneous-class': [
			'error',
			{
				allowConstructorOnly: false,
				allowEmpty: false,
				allowStaticOnly: false,
				allowWithDecorator: true
			}
		],

		// Disabled because of https://github.com/typescript-eslint/typescript-eslint/issues/647
		// '@typescript-eslint/no-floating-promises': 'error',

		'@typescript-eslint/no-for-in-array': 'error',
		'@typescript-eslint/no-inferrable-types': 'error',
		'@typescript-eslint/no-misused-new': 'error',
		'@typescript-eslint/no-misused-promises': [
			'error',
			{
				checksConditionals: true,

				// TODO: I really want this to be `true`, but it makes it inconvenient to use
				// async functions as event handlers... I need to find a good way to handle that.
				// https://github.com/sindresorhus/refined-github/pull/2391#discussion_r318990466
				checksVoidReturn: false
			}
		],

		// TODO: Enable this again when I target ESM output in all my TypeScript projects
		// '@typescript-eslint/no-namespace': 'error',

		'@typescript-eslint/no-non-null-asserted-optional-chain': 'error',

		// Disabled until this is resolved:
		// https://github.com/typescript-eslint/typescript-eslint/issues/202
		// '@typescript-eslint/no-non-null-assertion': 'error',

		// TODO: Enable this again when I target ESM output in all my TypeScript projects
		// '@typescript-eslint/no-require-imports': 'error',

		'@typescript-eslint/no-this-alias': [
			'error',
			{
				allowDestructuring: true
			}
		],
		'no-throw-literal': 'off',
		'@typescript-eslint/no-throw-literal': 'error',

		// TODO: Reconsider enabling this again in 2020.
		// Disable because it has too many false-positives: https://github.com/typescript-eslint/typescript-eslint/search?q=no-unnecessary-condition+is%3Aissue&state=open&type=Issues
		// '@typescript-eslint/no-unnecessary-condition': [
		// 	'error',
		// 	{
		// 		ignoreRhs: true,
		// 		checkArrayPredicates: true
		// 	}
		// ],

		'@typescript-eslint/no-unnecessary-qualifier': 'error',
		'@typescript-eslint/no-unnecessary-type-arguments': 'error',
		'@typescript-eslint/no-unnecessary-type-assertion': 'error',
		'no-unused-expressions': 'off',
		'@typescript-eslint/no-unused-expressions': 'error',
		'no-unused-vars': 'off',
		'@typescript-eslint/no-unused-vars': [
			'error',
			{
				vars: 'all',
				args: 'after-used',
				ignoreRestSiblings: true,
				argsIgnorePattern: /^_/.source,
				caughtErrors: 'all',
				caughtErrorsIgnorePattern: /^_$/.source
			}
		],

		// Disabled for now as it's marked as experimental.
		// '@typescript-eslint/no-unused-vars-experimental': 'error',

		'no-useless-constructor': 'off',
		'@typescript-eslint/no-useless-constructor': 'error',
		'@typescript-eslint/no-var-requires': 'error',
		'@typescript-eslint/prefer-for-of': 'error',
		'@typescript-eslint/prefer-function-type': 'error',
		'@typescript-eslint/prefer-includes': 'error',
		'@typescript-eslint/prefer-namespace-keyword': 'error',
		'@typescript-eslint/prefer-nullish-coalescing': 'error',
		'@typescript-eslint/prefer-optional-chain': 'error',
		'@typescript-eslint/prefer-readonly': 'error',
		'@typescript-eslint/prefer-string-starts-ends-with': 'error',
		'@typescript-eslint/promise-function-async': [
			'error',
			{
				allowAny: true
			}
		],
		quotes: 'off',
		'@typescript-eslint/quotes': [
			'error',
			'single'
		],
		'@typescript-eslint/restrict-plus-operands': 'error',
		'@typescript-eslint/restrict-template-expressions': [
			'error',
			{
				allowNumber: true
			}
		],
		'@typescript-eslint/return-await': 'error',
		'@typescript-eslint/require-array-sort-compare': 'error',

		// Disabled for now. It's too buggy. It fails to detect when try/catch is used, await inside blocks, etc. It's also common to have async functions without await for various reasons.
		// 'require-await': 'off',
		// '@typescript-eslint/require-await': 'error',

		'space-before-function-paren': 'off',
		'@typescript-eslint/space-before-function-paren': [
			'error',
			{
				anonymous: 'always',
				named: 'never',
				asyncArrow: 'always'
			}
		],
		semi: 'off',
		'@typescript-eslint/semi': [
			'error',
			'always'
		],

		// TODO: Reconsider enabling it again in 2021.
		// Disabled for now as it's too strict.
		// Relevant discussion: https://github.com/sindresorhus/refined-github/pull/2521#discussion_r343013852
		// '@typescript-eslint/strict-boolean-expressions': [
		// 	'error',
		// 	{
		// 		allowNullable: true,
		// 		allowSafe: true
		// 	}
		// ],

		'@typescript-eslint/triple-slash-reference': [
			'error',
			{
				path: 'never',

				// Cannot enable this until `@types/node` no longer has the `NodeJS` global
				// types: 'never'
			}
		],
		'@typescript-eslint/type-annotation-spacing': 'error',

		// Disabled as it crashes on most code
		// '@typescript-eslint/unbound-method': [
		// 	'error',
		// 	{
		// 		ignoreStatic: true
		// 	}
		// ],

		'@typescript-eslint/prefer-regexp-exec': 'error',
		'@typescript-eslint/unified-signatures': 'error',

		// TypeScript supports these features
		'no-useless-catch': 'error',

		// The rule is deprecated in ESLint and it doesn't fully make sense for TypeScript.
		// TODO: Remove this when the rule is removed from XO.
		'valid-jsdoc': 'off',

		// Disabled because of https://github.com/typescript-eslint/typescript-eslint/issues/60
		'no-redeclare': 'off',
	}
};