.eslintrc.js

module.exports = {
	root: true,
	extends: ['prettier'],
	parser: 'babel-eslint',
	parserOptions: {
		sourceType: 'module',
	},

	// TODO restore non-prettier stuff that we may still want.
	//
	env: {
		browser: true,
		node: true,
		es6: true,
	},
	// required to lint *.vue files
	plugins: [
		'json', // TODO JOE not working, doesn't seem to do anything with JSON files
		'promise', // https://github.com/xjamundx/eslint-plugin-promise
		'html',
	],
	// add your custom rules here
	rules: {
		// allow debugger during development
		'no-debugger': process.env.NODE_ENV && process.env.NODE_ENV.startsWith('dev') ? 0 : 2,

		'prefer-const': 'error',
		'one-var': ['off'],
		'no-var': 'error',
		'no-return-assign': ['error', 'except-parens'],
		'brace-style': ['error', '1tbs', {allowSingleLine: false}],
		'quote-props': ['error', 'as-needed'],
		curly: ['off', 'multi-or-nest', 'consistent'],

		'padding-line-between-statements': [
			'off',
			//
			// {
			//   blankLine: 'always',
			//   prev: '*',
			//   next: ['block', 'const', 'let', 'var', 'import', 'export'],
			// },
			// {
			//   blankLine: 'always',
			//   next: '*',
			//   prev: ['block', 'const', 'let', 'var', 'import', 'export'],
			// },
			//
			// { blankLine: 'never', prev: 'const', next: 'const' },
			// { blankLine: 'never', prev: 'let', next: 'let' },
			// { blankLine: 'never', prev: 'var', next: 'var' },
			// { blankLine: 'never', prev: 'import', next: 'import' },
			// { blankLine: 'never', prev: 'export', next: 'export' },
			//
			// {
			//   blankLine: 'always',
			//   prev: '*',
			//   next: [
			//     'multiline-block-like',
			//     'multiline-expression',
			//     'class',
			//     'function',
			//   ],
			// },
			// {
			//   blankLine: 'always',
			//   next: '*',
			//   prev: [
			//     'multiline-block-like',
			//     'multiline-expression',
			//     'class',
			//     'function',
			//   ],
			// },
		],

		// from https://github.com/xjamundx/eslint-plugin-promise
		'promise/always-return': 'off',
		'promise/no-return-wrap': 'error',
		'promise/param-names': 'error',
		'promise/catch-or-return': 'error',
		'promise/no-new-statics': 'error',
		'promise/no-return-in-finally': 'error',
	},

	settings: {
		// from https://www.npmjs.com/package/eslint-plugin-html
		//
		// Linting the JavaScript inside the HTML files works without the
		// following settings enabled, just by having "html" plugin enabled
		// above.
		//
		// Not sure why these have to be inside "settings". See
		// https://github.com/BenoitZugmeyer/eslint-plugin-html/issues/104
		//
		// TODO Not sure how these work, I seem to get errors no matter what
		// indentation I try. See
		// https://github.com/BenoitZugmeyer/eslint-plugin-html/issues/105
		//
		// 'html/html-extensions': ['.html'],
		// 'html/indent': '+2',
		// 'html/report-bad-indent': 'error',
	},

	overrides: [
		{
			files: ['*.ts', '*.tsx'],
			parser: 'typescript-eslint-parser',
			parserOptions: {
				ecmaFeatures: {
					jsx: true,
				},
			},

			// TODO restore non-prettier stuff that we may still want.
			//
			plugins: ['typescript'],
			rules: {
				// these are off because TypeScript handles these, and ESLint otherwise gets false positives on these.
				// See: https://github.com/eslint/typescript-eslint-parser/issues/208
				'no-undef': 0,
				'no-unused-vars': 0,

				// typescript-specific rules
				'typescript/adjacent-overload-signatures': 'error', // — Require that member overloads be consecutive
				'typescript/class-name-casing': 'error', // — Require PascalCased class and interface names (class-name from TSLint)
				'typescript/explicit-function-return-type': [
					'error',
					{
						allowExpressions: true,
					},
				], // — Require explicit return types on functions and class methods
				// 'typescript/explicit-member-accessibility': , // — Require explicit accessibility modifiers on class properties and methods (member-access from TSLint)
				// 'typescript/interface-name-prefix': , // — Require that interface names be prefixed with I (interface-name from TSLint)
				'typescript/member-delimiter-style': [
					'off',
					{
						// — Require a specific member delimiter style for interfaces and type literals
						delimiter: 'none',
						requireLast: true,
						ignoreSingleLine: true,
					},
				],
				// 'typescript/member-naming': , // — Enforces naming conventions for class members by visibility.
				// 'typescript/member-ordering': , // — Require a consistent member declaration order (member-ordering from TSLint)
				'typescript/no-angle-bracket-type-assertion': 'error', // — Enforces the use of as Type assertions instead of <Type> assertions (no-angle-bracket-type-assertion from TSLint)
				'typescript/no-array-constructor': 'error', // — Disallow generic Array constructors
				// 'typescript/no-empty-interface': , // — Disallow the declaration of empty interfaces (no-empty-interface from TSLint)
				'typescript/no-explicit-any': 'off', // — Disallow usage of the any type (no-any from TSLint)
				'typescript/no-inferrable-types': 'off', // — Disallows explicit type declarations for variables or parameters initialized to a number, string, or boolean. (no-inferrable-types from TSLint)
				'typescript/no-namespace': 'error', // — Disallow the use of custom TypeScript modules and namespaces
				// 'typescript/no-non-null-assertion': , // — Disallows non-null assertions using the ! postfix operator (no-non-null-assertion from TSLint)
				// 'typescript/no-parameter-properties': , // — Disallow the use of parameter properties in class constructors. (no-parameter-properties from TSLint)
				'typescript/no-triple-slash-reference': 'error', // — Disallow /// <reference path="" /> comments (no-reference from TSLint)
				// 'typescript/no-type-alias': , // — Disallow the use of type aliases (interface-over-type-literal from TSLint)
				'typescript/no-unused-vars': 'error', // — Prevent TypeScript-specific constructs from being erroneously flagged as unused
				// 'typescript/no-use-before-define': , // — Disallow the use of variables before they are defined
				'typescript/no-var-requires': 'off', // — Disallows the use of require statements except in import statements (no-var-requires from TSLint)
				// 'typescript/prefer-namespace-keyword': , // — Require the use of the namespace keyword instead of the module keyword to declare custom TypeScript modules. (no-internal-module from TSLint)
				'typescript/type-annotation-spacing': ['off', {}], // — Require consistent spacing around type annotations
			},
		},
	],
}