eslint.config.mjs

import tsESLintParser from '@typescript-eslint/parser'
import tsESLintPlugin from '@typescript-eslint/eslint-plugin'
import stylisticTSLint from '@stylistic/eslint-plugin'
import vueParser from 'vue-eslint-parser'
import pluginVue from 'eslint-plugin-vue'

export default [
  {
    // With the new flat configs, we unfortunately have to ignore everything
    // manually that we don't want linted.
    ignores: [
      '**/*.mjs',
      '*.js',
      'scripts/**/*.js',
      'resources/**/*.js',
      '.webpack/**/*.js'
    ]
  },
  // This extends the following configs:
  {
    plugins: {
      '@typescript-eslint': tsESLintPlugin
    },
    rules: {
      ...tsESLintPlugin.configs.recommended.rules
    }
  },
  // flat/recommended === vue3-recommended
  ...pluginVue.configs['flat/recommended'],
  // Our manual extensions:
  {
    files: ['source/**/*.{ts,vue,js}'],
    plugins: {
      // The keys here must correspond to the plugin namespaces referred below
      '@typescript-eslint': tsESLintPlugin,
      '@stylistic': stylisticTSLint,
      vue: pluginVue
    },
    languageOptions: {
      parserOptions: {
        parser: tsESLintParser,
        project: './tsconfig.json',
        extraFileExtensions: ['.vue'],
        ecmaVersion: 2018
      },
      parser: vueParser
    },
    rules: {
      ////////////////////////// STYLISTIC RULES ///////////////////////////////

      // Disallow semicolons except where absolutely necessary
      '@stylistic/semi': [ 'error', 'never' ],
      // Require multi-line arrays to have brackets on their own line
      '@stylistic/array-bracket-newline': [ 'error', 'consistent' ],
      '@stylistic/array-bracket-spacing': [
        'error',
        'always',
        { objectsInArrays: false, singleValue: false }
      ],
      '@stylistic/arrow-spacing': [ 'error' ],
      '@stylistic/brace-style': [ 'error', '1tbs', { allowSingleLine: true }],
      '@stylistic/dot-location': [ 'error', 'property' ],
      '@stylistic/eol-last': [ 'error', 'always' ],
      '@stylistic/indent': [ 'error', 2 ],
      // Enforce single quotes across the codebase except where backticks are
      // necessary (-> template strings) or it would avoid escaping (-> "'...'")
      '@stylistic/quotes': [ 'error', 'single', { avoidEscape: true } ],
      // Enforce proper spacing in objects ({ a: 1 } instead of {a:1})
      '@stylistic/object-curly-spacing': [ 'error', 'always' ],
      '@stylistic/space-before-function-paren': [ 'error', 'always' ],

      /////////////////////// END STYLISTIC RULES //////////////////////////////

      ////////////////////////// TYPESCRIPT RULES //////////////////////////////

      // Enforce using the `type` keyword to import names when only used as
      // types. This is especially necessary when cross-importing interfaces and
      // APIs for use in IPC calls between renderers and main. Most modules rely
      // on APIs that only either exist in the main process (e.g., Electron
      // imports) or the renderer (e.g., certain locale-dependent APIs).
      // Importing interfaces from the respective other domain without the
      // `type` keyword causes webpack to fully transclude the entire module in
      // the corresponding part of the code, resulting in runtime errors.
      // However, when we only need types and interfaces, using the `type`
      // keyword ensures that the corresponding import is only used by
      // TypeScript for checking types, but the import will be removed before
      // webpack sees it, meaning that webpack won't cross-pollute the various
      // parts of the app. This is also the reason for the `fixStyle` option
      // below, making this accidental leakage less likely.
      '@typescript-eslint/consistent-type-imports': [ 'error', {
        prefer: 'type-imports', fixStyle: 'separate-type-imports'
      } ],

      // Currently, there are about 260 uses of `any`. NOTE January 19, 2026:
      // Moved from "off" to "warn" to start making the type system more strict.
      '@typescript-eslint/no-explicit-any': 'warn',
      // Avoid the use of `delete`
      '@typescript-eslint/no-dynamic-delete': 'error',
      // Disallow unused variables, except for when they are named "event",
      // start with an underscore, are errors in try-catch blocks, or
      // destructured arrays.
      '@typescript-eslint/no-unused-expressions': 'error',
      '@typescript-eslint/no-unused-vars': [
        'error',
        {
          // See https://typescript-eslint.io/rules/no-unused-vars/
          // Allow ignoring function arguments by prefixing it with _
          // Also, we often have unused event-arguments in event handler
          // functions because they are detached from the addEventListener calls
          // and this helps faster parsing what a listener is for.
          argsIgnorePattern: '^(?:_|event)',
          // Don't report unused errors in try-catch blocks
          caughtErrors: 'none',
          // Always allow array destructuring with unused elements
          destructuredArrayIgnorePattern: '.*'
        }
      ],

      // Sometimes, it makes sense to return a void to save a line of code, so we
      // keep this rule off.
      '@typescript-eslint/no-confusing-void-expression': 'off',

      // If we activate this rule, we have about 500 errors that there are no
      // spaces around | operators. Hasn't been a problem until now, won't be
      // one in the future.
      '@typescript-eslint/space-infix-ops': 'off',
      '@typescript-eslint/no-base-to-string': [
        'error',
        {
          ignoredTypeNames: ['Text']
        }
      ],
      '@typescript-eslint/no-non-null-assertion': 'off',
      // DEBUG: Turn a few errors into warnings after upgrading ESLint to >6.x
      // This rule is difficult to disable right now; it interferes with the
      // "no-null-assertion" rule, and it won't be an easy fix. We'll have to
      // think about it.
      '@typescript-eslint/non-nullable-type-assertion-style': 1,
      '@typescript-eslint/no-unnecessary-boolean-literal-compare': 'error',
      '@typescript-eslint/strict-boolean-expressions': 'error',
      // The following rule basically disallows use of `any`
      '@typescript-eslint/no-unsafe-argument': 1,
      // Mark forgotten awaits as errors
      '@typescript-eslint/no-floating-promises': 'error',

      /////////////////////// END TYPESCRIPT RULES /////////////////////////////

      /////////////////////// ESLINT DEFAULT RULES /////////////////////////////

      'curly': [ 'error', 'all' ],

      // The following rule-changes to JSStandard Coding Style are tradition,
      // as they were included with the default configuration of Atom's ESLint
      // plugin, so we'll keep them here for the time being.
      'prefer-const': 'off',

      ///////////////////// END ESLINT DEFAULT RULES ///////////////////////////

      //////////////////////////// VUE RULES ///////////////////////////////////

      // Here follow vue-styles. While the short form is recommended
      // I tend to value verbose code. At least for now, discussion is
      // well received.
      'vue/v-bind-style': [ 'error', 'longform' ],
      'vue/v-on-style': [ 'error', 'longform' ],
      // Let the implementation decide if self-closing is wanted or not.
      'vue/html-self-closing': [
        'warn',
        {
          html: {
            void: 'any',
            normal: 'any',
            component: 'any'
          },
          svg: 'any',
          math: 'any'
        }
      ],
      // Allow up to three attributes per line so that the contributor can
      // decide if the attributes are too long for the 80 character column
      'vue/max-attributes-per-line': [
        'error',
        {
          singleline: 3,
          multiline: 3
        }
      ],
      // We allow the use of v-html directives, because we sanitize any user
      // provided HTML to only contain safe tags. The only stuff we currently
      // put in there is translation strings, which we sanitise in the trans()
      // function. NOTE to keep this on my mind!
      'vue/no-v-html': 'error'

      ////////////////////////// END VUE RULES /////////////////////////////////
    }
  }
]