MAGETWO-88336: [Backport] JS merging fails when JS bundling is enabled and bundle folder contains any other files

Author: Yevhen Miroshnychenko

app/code/Magento/RequireJs/Model/FileManager.php

@@ -164,6 +164,9 @@ public function createBundleJsPool()
             }
 
             foreach ($libDir->read($bundleDir) as $bundleFile) {
+                if (pathinfo($bundleFile, PATHINFO_EXTENSION) !== 'js') {
+                    continue;
+                }
                 $relPath = $libDir->getRelativePath($bundleFile);
                 $bundles[] = $this->assetRepo->createArbitrary($relPath, '');
             }

app/code/Magento/RequireJs/Test/Unit/Model/FileManagerTest.php

@@ -150,7 +150,7 @@ public function testCreateBundleJsPool()
             ->expects($this->once())
             ->method('read')
             ->with('path/to/bundle/dir/js/bundle')
-            ->willReturn(['bundle1.js', 'bundle2.js']);
+            ->willReturn(['bundle1.js', 'bundle2.js', 'some_file.not_js']);
         $dirRead
             ->expects($this->exactly(2))
             ->method('getRelativePath')