Run tests in a native Node.js ESM environment (#13966)

packages/babel-parser/test/estree-throws.js

@@ -6,8 +6,7 @@ import { fileURLToPath } from "url";
 runFixtureTestsWithoutExactASTMatch(
   path.join(path.dirname(fileURLToPath(import.meta.url)), "fixtures"),
   (input, options = {}) => {
-    options.plugins = options.plugins || [];
-    options.plugins.push("estree");
-    return parse(input, options);
+    const plugins = options.plugins || [];
+    return parse(input, { ...options, plugins: plugins.concat("estree") });
   },
 );

packages/babel-parser/test/helpers/runFixtureTests.js

@@ -218,7 +218,7 @@ function runTest(test, parseFunction, compareErrorsOnly = false) {
       return save(test, ast);
     }
 
-    if (ast.errors?.length) {
+    if (ast.errors && ast.errors.length) {
       throw new Error(
         `Expected non-recoverable error message: ${
           opts.throws

packages/babel-parser/test/package.json

@@ -0,0 +1 @@
+{ "type": "module" }