fix: Fix support for custom extensions from babel (#39)

src/index.js

@@ -30,13 +30,6 @@ function getPlugins(file, target) {
   }
 }
 
-function opts(file, config) {
-  return {
-    ...config,
-    basedir: path.dirname(file),
-  };
-}
-
 exports.interfaceVersion = 2;
 
 /**
@@ -60,15 +53,29 @@ exports.resolve = (source, file, options) => {
       cwd: plugin[1] && plugin[1].cwd ? plugin[1].cwd : config.cwd,
       root: config.root.concat(plugin[1] && plugin[1].root ? plugin[1].root : []),
       alias: Object.assign(config.alias, plugin[1] ? plugin[1].alias : {}),
+      extensions: plugin[1] && plugin[1].extensions ? plugin[1].extensions : config.extensions,
     }), { root: [], alias: {}, cwd: projectRootDir });
 
     const manipulatedOpts = babelModuleResolver.manipulatePluginOptions(pluginOpts);
+
     const src = babelModuleResolver.mapModule(
       source, file, manipulatedOpts, path.resolve(manipulatedOpts.cwd),
     );
+
+    const extensions = options.extensions ||
+      manipulatedOpts.extensions ||
+      babelModuleResolver.defaultExtensions;
+
     return {
       found: true,
-      path: resolve.sync(src || source, opts(file, options)),
+      path: resolve.sync(
+        src || source,
+        {
+          ...options,
+          extensions,
+          basedir: path.dirname(file),
+        },
+      ),
     };
   } catch (e) {
     return { found: false };

test/.babelrc

@@ -5,7 +5,8 @@
       "alias": {
         "components": "./test/examples/components",
         "underscore": "npm:lodash"
-      }
+      },
+      "extensions": [".js", ".customExt"]
     }]
   ],
   "env": {

test/index.test.js

@@ -40,6 +40,14 @@ describe('eslint-import-resolver-module-resolver', () => {
       });
   });
 
+  it('should return `true` when the file uses a custom extension from the babel plugin', () => {
+    expect(resolverPlugin.resolve('components/customFile', path.resolve('./test/examples/components/c1.js'), opts))
+      .toEqual({
+        found: true,
+        path: path.resolve(__dirname, './examples/components/customFile.customExt'),
+      });
+  });
+
   it('should return `true` when no mapping is required', () => {
     expect(resolverPlugin.resolve('./sub/sub/c2', path.resolve('./test/examples/components/c1'), opts))
       .toEqual({