eng, upgrade to eslint 9 (#3041)

Author: weidongxu-microsoft

typespec-extension/.eslintignore

@@ -0,0 +1,109 @@
+// @ts-check
+import eslint from "@eslint/js";
+import unicorn from "eslint-plugin-unicorn";
+import tsEslint from "typescript-eslint";
+
+/** Config that will apply to all files */
+const allFilesConfig = tsEslint.config({
+  plugins: {
+    unicorn,
+  },
+  rules: {
+    /**
+     * Typescript plugin overrides
+     */
+    "@typescript-eslint/no-non-null-assertion": "off",
+    "@typescript-eslint/no-explicit-any": "off",
+    "@typescript-eslint/no-inferrable-types": "off",
+    "@typescript-eslint/no-empty-function": "off",
+    "@typescript-eslint/no-empty-interface": "off",
+    "@typescript-eslint/no-empty-object-type": "off",
+    "@typescript-eslint/no-unused-vars": [
+      "warn",
+      {
+        varsIgnorePattern: "^_",
+        argsIgnorePattern: ".*",
+        ignoreRestSiblings: true,
+        caughtErrorsIgnorePattern: ".*",
+      },
+    ],
+
+    // This rule is bugged https://github.com/typescript-eslint/typescript-eslint/issues/6538
+    "@typescript-eslint/no-misused-promises": "off",
+    "@typescript-eslint/no-unused-expressions": [
+      "warn",
+      { allowShortCircuit: true, allowTernary: true },
+    ],
+
+    /**
+     * Unicorn
+     */
+    "unicorn/filename-case": ["error", { case: "kebabCase" }],
+
+    /**
+     * Core
+     */
+    "no-inner-declarations": "off",
+    "no-empty": "off",
+    "no-constant-condition": "off",
+    "no-case-declarations": "off",
+    "no-ex-assign": "off",
+    "no-undef": "off",
+    "prefer-const": [
+      "warn",
+      {
+        destructuring: "all",
+      },
+    ],
+    eqeqeq: ["warn", "always", { null: "ignore" }],
+
+    // Do not want console.log left from debugging or using console.log for logging. Use the program logger.
+    "no-console": "warn",
+
+    // Symbols should have a description so it can be serialized.
+    "symbol-description": "warn",
+  },
+});
+
+/** Config that will apply to all typescript files only
+ * @param {string} root
+ */
+export function getTypeScriptProjectRules(root) {
+  return tsEslint.config({
+    files: [
+      "**/src/**/*.ts",
+    ],
+    plugins: {},
+    languageOptions: {
+      parserOptions: {
+        projectService: {
+          allowDefaultProject: ["vitest.config.ts"],
+        },
+        tsconfigRootDir: root,
+      },
+    },
+    rules: {
+      // Only put rules here that need typescript project information
+      "@typescript-eslint/no-floating-promises": "error",
+      "@typescript-eslint/no-deprecated": "warn",
+    },
+  });
+}
+
+export const TypeSpecCommonEslintConfigs = [
+  eslint.configs.recommended,
+  ...tsEslint.configs.recommended,
+  ...allFilesConfig,
+];
+
+export default tsEslint.config(
+  {
+    ignores: [
+      "**/dist/**/*",
+      "**/temp/**/*",
+      "generator/**/*",
+    ],
+  },
+  ...TypeSpecCommonEslintConfigs,
+  ...getTypeScriptProjectRules(import.meta.dirname),
+);