Infrastructure: Upgrade to ESLint 9 (#3011)

Bumps:
* eslint from 8.57.0 to 9.4.0
* eslint-plugin-ava from 14.0.0 to 15.0.0

Adds:
* globals 15.1.0

Removes:
* eslint-plugin-prettier

.link-checker.js

@@ -7,7 +7,8 @@ const HTMLParser = require('node-html-parser');
 // returns undefined.
 const getAttributeValue = (obj, attribute) => {
   if (typeof obj !== 'object' || obj === null) return undefined;
-  if (obj.hasOwnProperty(attribute)) return obj[attribute];
+  if (Object.prototype.hasOwnProperty.call(obj, attribute))
+    return obj[attribute];
 
   if (Array.isArray(obj)) {
     for (const element of obj) {

content/patterns/grid/examples/js/dataGrid.js

@@ -194,9 +194,10 @@ aria.Grid.prototype.isValidCell = function (row, col) {
  *  Returns whether or not the cell has been hidden.
  */
 aria.Grid.prototype.isHidden = function (row, col) {
+  // prettier-ignore
   var cell = this.gridNode
-    .querySelectorAll(aria.GridSelector.ROW)
-    [row].querySelectorAll(aria.GridSelector.CELL)[col];
+    .querySelectorAll(aria.GridSelector.ROW)[row]
+    .querySelectorAll(aria.GridSelector.CELL)[col];
   return aria.Utils.hasClass(cell, aria.CSSClass.HIDDEN);
 };
 

eslint.config.mjs

@@ -0,0 +1,124 @@
+import globals from 'globals';
+
+import js from '@eslint/js';
+import babelParser from '@babel/eslint-parser';
+
+import jsdoc from 'eslint-plugin-jsdoc';
+import html from 'eslint-plugin-html';
+import ava from 'eslint-plugin-ava';
+
+export default [
+  // Replaces .eslintignore
+  {
+    ignores: [
+      '**/*.min.js',
+      'common/',
+      'content/patterns/landmarks/examples/js/visua11y.js', // cspell:ignore visua
+      'content/shared/js/highlight.pack.js',
+      'content/shared/js/skipto.js',
+    ],
+  },
+  js.configs.recommended,
+  {
+    files: ['**/*.js'],
+
+    languageOptions: {
+      ecmaVersion: 2021,
+      parserOptions: {
+        ecmaFeatures: {
+          impliedStrict: false,
+        },
+      },
+      globals: {
+        ...globals.browser,
+      },
+      sourceType: 'script',
+    },
+
+    linterOptions: {
+      reportUnusedDisableDirectives: 'error',
+    },
+
+    plugins: {
+      jsdoc: jsdoc,
+    },
+
+    rules: {
+      ...jsdoc.configs.recommended.rules,
+      'jsdoc/no-undefined-types': 'off',
+      'jsdoc/require-jsdoc': 'off',
+      'jsdoc/require-param-description': 'off',
+      'jsdoc/require-param-type': 'off',
+      'jsdoc/require-returns-description': 'off',
+      'jsdoc/tag-lines': ['warn', 'any', { startLines: 1 }],
+      'no-console': 'error',
+      // https://eslint.org/docs/latest/use/migrate-to-9.0.0#no-unused-vars, but can be fixed
+      'no-unused-vars': ['error', { caughtErrors: 'none' }],
+      strict: [2, 'global'],
+    },
+  },
+  {
+    files: ['test/**/*.js'],
+
+    languageOptions: {
+      ecmaVersion: 'latest',
+      sourceType: 'commonjs',
+      globals: {
+        ...globals.node,
+      },
+    },
+
+    plugins: {
+      ava: ava,
+    },
+
+    rules: {
+      ...ava.configs.recommended.rules,
+      'no-restricted-properties': [
+        2,
+        {
+          property: 'findElements',
+          message: 'Please use t.context.queryElements().',
+        },
+      ],
+      strict: 'off',
+    },
+  },
+  {
+    files: ['scripts/*.js', '.link-checker.js'],
+
+    languageOptions: {
+      parser: babelParser,
+      ecmaVersion: 'latest',
+      parserOptions: {
+        requireConfigFile: false,
+      },
+      globals: {
+        ...globals.node,
+      },
+    },
+
+    rules: {
+      'no-console': 'off',
+      strict: 'off',
+    },
+  },
+  {
+    files: ['**/*.html'],
+
+    languageOptions: {
+      globals: {
+        sourceCode: true,
+      },
+    },
+
+    plugins: {
+      html: html,
+    },
+  },
+  {
+    files: ['**/*.mjs'],
+
+    languageOptions: { sourceType: 'module' },
+  },
+];