[eslint] Allow "latest" as ecmaVersion (#13638)

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

@@ -11,7 +11,7 @@ exports.normalizeESLintConfig = function (options) {
 
   return {
     babelOptions: { cwd: process.cwd(), ...babelOptions },
-    ecmaVersion,
+    ecmaVersion: ecmaVersion === "latest" ? 1e8 : ecmaVersion,
     sourceType,
     allowImportExportEverywhere,
     requireConfigFile,

eslint/babel-eslint-tests/test/integration/eslint/config.js

@@ -21,4 +21,23 @@ describe("ESLint config", () => {
     });
     expect(messages.length).toEqual(0);
   });
+
+  it('should allow ecmaVersion to be "latest"', () => {
+    const linter = new eslint.Linter();
+    linter.defineParser("@babel/eslint-parser", parser);
+    // ImportDeclarations result in a parser error if ecmaVersion < 2015 and sourceType != "module".
+    const messages = linter.verify('import { hello } from "greetings"', {
+      parser: "@babel/eslint-parser",
+      parserOptions: {
+        ecmaVersion: "latest",
+        babelOptions: {
+          configFile: path.resolve(
+            path.dirname(fileURLToPath(import.meta.url)),
+            "../../../../babel-eslint-shared-fixtures/config/babel.config.js",
+          ),
+        },
+      },
+    });
+    expect(messages.length).toEqual(0);
+  });
 });