Add requireConfigFile option

README.md

@@ -53,6 +53,7 @@ With the parser set, your configuration can be configured as described in the [C
 
 Additional configuration options can be set in your ESLint configuration under the `parserOptions` key. Please note that the `ecmaFeatures` config property may still be required for ESLint to work properly with features not in ECMAScript 5 by default.
 
+- `requireConfigFile` (default `true`) can be set to `false` to allow babel-eslint to run on files that do not have a Babel configuration associated with them. This can be useful for linting files that are not transformed by Babel (such as configuration files), though using [glob-based configuration](https://eslint.org/docs/user-guide/configuring#configuration-based-on-glob-patterns) to use the default parser for these files is recommended. Note that when no configuration file is found that babel-eslint will not parse any experimental syntax.
 - `sourceType` can be set to `"module"`(default) or `"script"` if your code isn't using ECMAScript modules.
 - `allowImportExportEverywhere` (default `false`) can be set to `true` to allow import and export declarations to appear anywhere a statement is allowed if your build environment supports that. Otherwise import and export declarations can only appear at a program's top level.
 - `ecmaFeatures.globalReturn` (default `false`) allow return statements in the global scope when used with `sourceType: "script"`.

lib/analyze-scope.js

@@ -323,7 +323,7 @@ module.exports = function(ast, parserOptions) {
         parserOptions.ecmaFeatures.globalReturn) === true,
     impliedStrict: false,
     sourceType: ast.sourceType,
-    ecmaVersion: parserOptions.ecmaVersion || 2018,
+    ecmaVersion: parserOptions.ecmaVersion,
     fallback,
   };
 

lib/index.js

@@ -16,7 +16,7 @@ exports.parse = function(code, options) {
   return exports.parseForESLint(code, options).ast;
 };
 
-exports.parseForESLint = function(code, options) {
+exports.parseForESLint = function(code, options = {}) {
   if (!IS_RUNNING_SUPPORTED_VERSION) {
     throw new Error(
       `babel-eslint@${
@@ -25,7 +25,6 @@ exports.parseForESLint = function(code, options) {
     );
   }
 
-  options = options || {};
   options.babelOptions = options.babelOptions || {};
   options.ecmaVersion = options.ecmaVersion || 2018;
   options.sourceType = options.sourceType || "module";

lib/parse.js

@@ -1,10 +1,15 @@
 "use strict";
 
 const babylonToEspree = require("./babylon-to-espree");
-const { parseSync: parse, tokTypes: tt, traverse } = require("@babel/core");
+const {
+  parseSync: parse,
+  tokTypes: tt,
+  traverse,
+  loadPartialConfig,
+} = require("@babel/core");
 
 module.exports = function(code, options) {
-  const opts = {
+  let opts = {
     sourceType: options.sourceType,
     filename: options.filePath,
     cwd: options.babelOptions.cwd,
@@ -35,7 +40,24 @@ module.exports = function(code, options) {
     },
   };
 
+  if (options.requireConfigFile !== false) {
+    const config = loadPartialConfig(opts);
+
+    if (config !== null) {
+      if (!config.hasFilesystemConfig()) {
+        throw new Error(
+          `No Babel config file detected for ${
+            config.options.filename
+          }. Either disable config file checking with requireConfigFile: false, or configure Babel so that it can find the config files.`
+        );
+      }
+
+      opts = config.options;
+    }
+  }
+
   let ast;
+
   try {
     ast = parse(code, opts);
   } catch (err) {