Fix parserOverride support in @babel/eslint-parser

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

@@ -15,7 +15,8 @@ module.exports = function maybeParse(code, options) {
       { dirname: __dirname, type: "plugin" },
     );
   }
-  options.plugins.push(extractParserOptionsConfigItem);
+  const { plugins } = options;
+  options.plugins = plugins.concat(extractParserOptionsConfigItem);
 
   try {
     return {
@@ -28,8 +29,10 @@ module.exports = function maybeParse(code, options) {
     }
   }
 
-  let ast;
+  // There was already a parserOverride, so remove our plugin.
+  options.plugins = plugins;
 
+  let ast;
   try {
     ast = babel.parseSync(code, options);
   } catch (err) {

eslint/babel-eslint-tests/test/fixtures/parser-override/babel.config.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["./plugin.js"]
+}

eslint/babel-eslint-tests/test/fixtures/parser-override/plugin.js

@@ -0,0 +1,9 @@
+const parser = require("@babel/parser");
+
+module.exports = function () {
+  return {
+    parserOverride(code, opts) {
+      return parser.parse(`foo;`, opts);
+    },
+  };
+};

eslint/babel-eslint-tests/test/integration/parser-override.js

@@ -0,0 +1,51 @@
+import path from "path";
+import { fileURLToPath } from "url";
+import { createRequire } from "module";
+import * as babelESLint from "@babel/eslint-parser";
+
+describe("parserOverride", () => {
+  const expectedAST = {
+    type: "Program",
+    body: [
+      {
+        type: "ExpressionStatement",
+        expression: {
+          type: "Identifier",
+          name: "foo",
+        },
+      },
+    ],
+  };
+
+  it("works when parsing in the main thread", () => {
+    const { ast } = babelESLint.parseForESLint(`27`, {
+      filename: "input.js",
+      babelOptions: {
+        configFile: path.resolve(
+          path.dirname(fileURLToPath(import.meta.url)),
+          "../fixtures/parser-override/babel.config.json",
+        ),
+      },
+    });
+
+    expect(ast).toMatchObject(expectedAST);
+  });
+
+  const babel7node12 = parseInt(process.versions.node) < 12 ? it.skip : it;
+  babel7node12("works when parsing in a worker", async () => {
+    const require = createRequire(import.meta.url);
+    const babelESLintWorker = require("@babel/eslint-parser/experimental-worker");
+
+    const { ast } = babelESLintWorker.parseForESLint(`27`, {
+      filename: "input.js",
+      babelOptions: {
+        configFile: path.resolve(
+          path.dirname(fileURLToPath(import.meta.url)),
+          "../fixtures/parser-override/babel.config.json",
+        ),
+      },
+    });
+
+    expect(ast).toMatchObject(expectedAST);
+  });
+});