Add eslint config

Signed-off-by: Knut Ahlers <knut@ahlers.me>

.eslintrc.js

@@ -0,0 +1,122 @@
+/*
+ * Hack to automatically load globally installed eslint modules
+ * on Archlinux systems placed in /usr/lib/node_modules
+ *
+ * Source: https://github.com/eslint/eslint/issues/11914#issuecomment-569108633
+ */
+
+const Module = require('module')
+
+const hacks = [
+  'babel-eslint',
+  'eslint-plugin-vue',
+]
+
+const ModuleFindPath = Module._findPath
+Module._findPath = (request, paths, isMain) => {
+  const r = ModuleFindPath(request, paths, isMain)
+  if (!r && hacks.includes(request)) {
+    return require.resolve(`/usr/lib/node_modules/${request}`)
+  }
+  return r
+}
+
+// https://eslint.org/docs/user-guide/configuring
+
+module.exports = {
+  env: {
+    browser: true,
+    node: true,
+  },
+
+  extends: [
+    'plugin:vue/strongly-recommended',
+    // https://github.com/standard/standard/blob/master/docs/RULES-en.md
+    'eslint:recommended',
+  ],
+
+  globals: {
+    process: true,
+  },
+
+  parserOptions: {
+    ecmaVersion: 2020,
+    parser: 'babel-eslint',
+  },
+
+  plugins: [
+    // required to lint *.vue files
+    'vue',
+  ],
+
+  root: true,
+
+  // add your custom rules here
+  rules: {
+    'array-bracket-newline': ['error', { multiline: true }],
+    'array-bracket-spacing': ['error'],
+    'arrow-body-style': ['error', 'as-needed'],
+    'arrow-parens': ['error', 'as-needed'],
+    'arrow-spacing': ['error', { after: true, before: true }],
+    'block-spacing': ['error'],
+    'brace-style': ['error', '1tbs'],
+    'comma-dangle': ['error', 'always-multiline'], // Apply Contentflow rules
+    'comma-spacing': ['error'],
+    'comma-style': ['error', 'last'],
+    'curly': ['error'],
+    'dot-location': ['error', 'property'],
+    'dot-notation': ['error'],
+    'eol-last': ['error', 'always'],
+    'eqeqeq': ['error', 'always', { null: 'ignore' }],
+    'func-call-spacing': ['error', 'never'],
+    'function-paren-newline': ['error', 'multiline'],
+    'generator-star-spacing': ['off'], // allow async-await
+    'implicit-arrow-linebreak': ['error'],
+    'indent': ['error', 2],
+    'key-spacing': ['error', { afterColon: true, beforeColon: false, mode: 'strict' }],
+    'keyword-spacing': ['error'],
+    'linebreak-style': ['error', 'unix'],
+    'lines-between-class-members': ['error'],
+    'multiline-comment-style': ['warn'],
+    'newline-per-chained-call': ['error'],
+    'no-console': ['off'],
+    'no-debugger': process.env.NODE_ENV === 'production' ? 'error' : 'off', // allow debugger during development
+    'no-duplicate-imports': ['error'],
+    'no-else-return': ['error'],
+    'no-extra-parens': ['error'],
+    'no-implicit-coercion': ['error'],
+    'no-lonely-if': ['error'],
+    'no-multi-spaces': ['error'],
+    'no-multiple-empty-lines': ['warn', { max: 2, maxBOF: 0, maxEOF: 0 }],
+    'no-trailing-spaces': ['error'],
+    'no-unneeded-ternary': ['error'],
+    'no-useless-return': ['error'],
+    'no-var': ['error'],
+    'no-whitespace-before-property': ['error'],
+    'object-curly-newline': ['error', { consistent: true }],
+    'object-curly-spacing': ['error', 'always'],
+    'object-shorthand': ['error'],
+    'padded-blocks': ['error', 'never'],
+    'prefer-arrow-callback': ['error'],
+    'prefer-const': ['error'],
+    'prefer-object-spread': ['error'],
+    'prefer-rest-params': ['error'],
+    'prefer-template': ['error'],
+    'quote-props': ['error', 'consistent-as-needed', { keywords: false }],
+    'quotes': ['error', 'single', { allowTemplateLiterals: true }],
+    'semi': ['error', 'never'],
+    'sort-imports': ['error', { ignoreCase: true, ignoreDeclarationSort: false, ignoreMemberSort: false }],
+    'sort-keys': ['error', 'asc', { caseSensitive: true, natural: false }],
+    'space-before-blocks': ['error', 'always'],
+    'space-before-function-paren': ['error', 'never'],
+    'space-in-parens': ['error', 'never'],
+    'space-infix-ops': ['error'],
+    'space-unary-ops': ['error', { nonwords: false, words: true }],
+    'spaced-comment': ['warn', 'always'],
+    'switch-colon-spacing': ['error'],
+    'template-curly-spacing': ['error', 'never'],
+    'unicode-bom': ['error', 'never'],
+    'wrap-iife': ['error'],
+    'yoda': ['error'],
+  },
+}