Fix error when parsing ignored files with @babel/eslint-parser (#13338)

* fix(babel-eslint-parser): prevent typeerror in maybeParse
* fix(babel-eslint-parser): prevent other typeerrors in convert modules
* test(babel-eslint-parser): test maybeParse when file is ignored
* refactor(babel-eslint-parser): use fallback options instead of typeerror protections

Co-authored-by: devfservant <43757707+devfservant@users.noreply.github.com>
Co-authored-by: François Servant <francois.servant.e@thalesdigital.io>

eslint/babel-eslint-parser/src/worker/configuration.cjs

@@ -58,15 +58,37 @@ function validateResolvedConfig(config, options) {
   }
 }
 
+function getDefaultParserOptions(options) {
+  return {
+    plugins: [],
+    ...options,
+    babelrc: false,
+    configFile: false,
+    browserslistConfigFile: false,
+    ignore: null,
+    only: null,
+  };
+}
+
 module.exports = function normalizeBabelParseConfig(options) {
   const parseOptions = normalizeParserOptions(options);
 
   if (process.env.BABEL_8_BREAKING) {
     return babel
       .loadPartialConfigAsync(parseOptions)
-      .then(config => validateResolvedConfig(config, options) || parseOptions);
+      .then(config => validateConfigWithFallback(config));
   } else {
     const config = babel.loadPartialConfigSync(parseOptions);
-    return validateResolvedConfig(config, options) || parseOptions;
+    return validateConfigWithFallback(config);
+  }
+
+  function validateConfigWithFallback(inputConfig) {
+    const result = validateResolvedConfig(inputConfig, options);
+    if (result) {
+      return result;
+    } else {
+      // Fallback when `loadPartialConfig` returns `null` (e.g.: when the file is ignored)
+      return getDefaultParserOptions(parseOptions);
+    }
   }
 };

eslint/babel-eslint-parser/test/index.js

@@ -5,9 +5,11 @@ import { fileURLToPath } from "url";
 import { createRequire } from "module";
 import { parseForESLint } from "../lib/index.cjs";
 
+const dirname = path.dirname(fileURLToPath(import.meta.url));
+
 const BABEL_OPTIONS = {
   configFile: path.resolve(
-    path.dirname(fileURLToPath(import.meta.url)),
+    dirname,
     "../../babel-eslint-shared-fixtures/config/babel.config.js",
   ),
 };
@@ -75,7 +77,7 @@ describe("Babel and Espree", () => {
     expect(babelAST).toEqual(espreeAST);
   }
 
-  beforeAll(async () => {
+  beforeAll(() => {
     const require = createRequire(import.meta.url);
 
     // Use the version of Espree that is a dependency of
@@ -88,7 +90,7 @@ describe("Babel and Espree", () => {
   });
 
   describe("compatibility", () => {
-    it("should allow ast.analyze to be called without options", function () {
+    it("should allow ast.analyze to be called without options", () => {
       const ast = parseForESLint("`test`", {
         eslintScopeManager: true,
         eslintVisitorKeys: true,
@@ -98,6 +100,16 @@ describe("Babel and Espree", () => {
         escope.analyze(ast);
       }).not.toThrow(new TypeError("Should allow no options argument."));
     });
+
+    it("should not crash when `loadPartialConfigSync` returns `null`", () => {
+      const thunk = () =>
+        parseForESLint("`test`", {
+          eslintScopeManager: true,
+          eslintVisitorKeys: true,
+          babelOptions: { filename: "test.js", ignore: [/./] },
+        });
+      expect(thunk).not.toThrow();
+    });
   });
 
   describe("templates", () => {