chore: bump ESLint stack to v15 and migrate to flat config

eslint.config.mjs

@@ -0,0 +1,109 @@
+import base, { createConfig } from '@metamask/eslint-config';
+import jest from '@metamask/eslint-config-jest';
+import nodejs from '@metamask/eslint-config-nodejs';
+import typescript from '@metamask/eslint-config-typescript';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const tsconfigRootDir = path.dirname(fileURLToPath(import.meta.url));
+
+const config = createConfig([
+  ...base,
+  {
+    ignores: ['coverage/**', 'dist/**', 'docs/**', '.yarn/**'],
+  },
+  {
+    linterOptions: {
+      reportUnusedDisableDirectives: 'error',
+    },
+  },
+  {
+    rules: {
+      // Handled by Oxfmt.
+      'prettier/prettier': 'off',
+      'import-x/order': 'off',
+    },
+  },
+  {
+    files: ['**/*.{js,cjs,mjs}', '**/*.test.{js,ts}', '**/tests/**/*.{js,ts}'],
+    extends: [nodejs],
+  },
+  {
+    files: ['**/*.{js,cjs}'],
+    languageOptions: {
+      sourceType: 'script',
+      ecmaVersion: 2020,
+    },
+  },
+  {
+    files: ['**/*.mjs'],
+    languageOptions: {
+      sourceType: 'module',
+    },
+  },
+  {
+    files: ['**/*.ts'],
+    extends: [typescript],
+    languageOptions: {
+      parserOptions: {
+        tsconfigRootDir,
+      },
+    },
+  },
+  {
+    files: ['**/*.test.{js,ts}', '**/tests/**/*.{js,ts}'],
+    extends: [jest],
+  },
+  // Project-wide rule overrides. These go after every `extends` so they win.
+  {
+    rules: {
+      // TODO: Re-enable these rules.
+      // They were not enforced under the legacy eslint-config v12, and fixing
+      // roughly 150 JSDoc blocks is out of scope for a config migration.
+      // `require-jsdoc` in particular must stay off while suppressed: its
+      // autofixer inserts empty `/** */` blocks and mangles surrounding code.
+      // Core disables it for the same reason.
+      'jsdoc/require-jsdoc': 'off',
+      'jsdoc/require-param-description': 'off',
+      'jsdoc/require-returns': 'off',
+      'jsdoc/tag-lines': 'off',
+    },
+  },
+  {
+    files: ['**/*.ts'],
+    rules: {
+      // TODO: Re-enable these rules.
+      // Newly surfaced by eslint-config v15; not enforced under v12.
+      '@typescript-eslint/explicit-function-return-type': 'off',
+      '@typescript-eslint/prefer-nullish-coalescing': 'off',
+    },
+  },
+  {
+    settings: {
+      // `uuid` ships an exports map that the TypeScript resolver cannot read,
+      // so `import-x` sees no named exports and false positives on `uuid.v4`.
+      'import-x/ignore': ['uuid'],
+    },
+  },
+  {
+    files: ['**/*.test-d.ts'],
+    rules: {
+      // In `tsd` type tests the assertions carry the meaning of the test, so
+      // the autofixer actively destroys them. Stripping `as any` from
+      // `expectAssignable<Json>(null as any)`, for instance, deletes the very
+      // thing that assertion exists to prove.
+      '@typescript-eslint/no-unnecessary-type-assertion': 'off',
+    },
+  },
+  {
+    files: ['**/*.test.{js,ts}'],
+    rules: {
+      // These tests deliberately reach for `crypto` and `crypto.webcrypto`,
+      // and polyfill the global when running on Node 18. Flagging them as
+      // unsupported defeats the purpose of the polyfill they are testing.
+      'n/no-unsupported-features/node-builtins': 'off',
+    },
+  },
+]);
+
+export default config;

package.json

@@ -52,7 +52,7 @@
     "lint:changelog": "auto-changelog validate --prettier",
     "lint:constraints": "yarn constraints",
     "lint:dependencies": "depcheck && yarn dedupe",
-    "lint:eslint": "eslint . --cache --ext js,ts",
+    "lint:eslint": "eslint . --cache",
     "lint:fix": "yarn lint:eslint --fix && yarn lint:constraints --fix && yarn lint:misc --write && yarn lint:dependencies && yarn lint:changelog",
     "lint:misc": "oxfmt --ignore-path .gitignore",
     "prepack": "./scripts/prepack.sh",
@@ -78,28 +78,28 @@
   "devDependencies": {
     "@lavamoat/allow-scripts": "^3.0.4",
     "@lavamoat/preinstall-always-fail": "^1.0.0",
-    "@metamask/auto-changelog": "^3.1.0",
-    "@metamask/eslint-config": "^12.0.0",
-    "@metamask/eslint-config-jest": "^12.0.0",
-    "@metamask/eslint-config-nodejs": "^12.0.0",
-    "@metamask/eslint-config-typescript": "^12.0.0",
+    "@metamask/auto-changelog": "^6.1.0",
+    "@metamask/eslint-config": "^15.0.0",
+    "@metamask/eslint-config-jest": "^15.0.0",
+    "@metamask/eslint-config-nodejs": "^15.0.0",
+    "@metamask/eslint-config-typescript": "^15.0.0",
     "@ts-bridge/cli": "^0.1.2",
     "@ts-bridge/shims": "^0.1.1",
     "@types/jest": "^28.1.7",
     "@types/jest-when": "^3.5.3",
     "@types/node": "~18.18.14",
+    "@types/semver": "^7",
     "@types/uuid": "^9.0.8",
-    "@typescript-eslint/eslint-plugin": "^5.43.0",
-    "@typescript-eslint/parser": "^5.43.0",
     "depcheck": "^1.4.7",
-    "eslint": "^8.44.0",
+    "eslint": "^9.39.1",
     "eslint-config-prettier": "^9.1.0",
-    "eslint-plugin-import": "^2.27.5",
-    "eslint-plugin-jest": "^27.2.2",
-    "eslint-plugin-jsdoc": "^39.9.1",
-    "eslint-plugin-n": "^15.7.0",
+    "eslint-import-resolver-typescript": "^3.6.3",
+    "eslint-plugin-import-x": "^4.3.0",
+    "eslint-plugin-jest": "^28.8.3",
+    "eslint-plugin-jsdoc": "^50.2.4",
+    "eslint-plugin-n": "^17.10.3",
     "eslint-plugin-prettier": "^5.2.1",
-    "eslint-plugin-promise": "^6.1.1",
+    "eslint-plugin-promise": "^7.1.0",
     "jest": "^29.2.2",
     "jest-it-up": "^2.0.2",
     "jest-when": "^3.6.0",
@@ -111,6 +111,7 @@
     "tsd": "^0.29.0",
     "typedoc": "^0.23.15",
     "typescript": "~5.3.3",
+    "typescript-eslint": "^8.48.0",
     "web3": "^4.16.0"
   },
   "resolutions": {
@@ -125,7 +126,8 @@
   "packageManager": "yarn@4.16.0",
   "lavamoat": {
     "allowScripts": {
-      "@lavamoat/preinstall-always-fail": false
+      "@lavamoat/preinstall-always-fail": false,
+      "eslint-plugin-import-x>unrs-resolver": false
     }
   }
 }