Issue #3163663 by mpp, chrisolof, alexpott, quietone: Too many open files...

Issue #3163663 by mpp, chrisolof, alexpott, quietone: Too many open files issue with migrating multiple files using "download" process plugin

core/modules/migrate/src/Plugin/migrate/process/Download.php

@@ -155,6 +155,10 @@ public function transform($value, MigrateExecutableInterface $migrate_executable
       throw new MigrateException("{$e->getMessage()} ($source)");
     }
 
+    if (is_resource($destination_stream)) {
+      fclose($destination_stream);
+    }
+
     return $final_destination;
   }
 

core/modules/migrate/tests/src/Kernel/process/DownloadTest.php

@@ -34,7 +34,7 @@ protected function setUp(): void {
    * Tests a download that overwrites an existing local file.
    */
   public function testOverwritingDownload() {
-    // Create a pre-existing file at the destination, to test overwrite behavior.
+    // Create a pre-existing file at the destination.
     $destination_uri = $this->createUri('existing_file.txt');
 
     // Test destructive download.
@@ -47,7 +47,7 @@ public function testOverwritingDownload() {
    * Tests a download that renames the downloaded file if there's a collision.
    */
   public function testNonDestructiveDownload() {
-    // Create a pre-existing file at the destination, to test overwrite behavior.
+    // Create a pre-existing file at the destination.
     $destination_uri = $this->createUri('another_existing_file.txt');
 
     // Test non-destructive download.
@@ -60,7 +60,7 @@ public function testNonDestructiveDownload() {
    * Tests that an exception is thrown if the destination URI is not writable.
    */
   public function testWriteProtectedDestination() {
-    // Create a pre-existing file at the destination, to test overwrite behavior.
+    // Create a pre-existing file at the destination.
     $destination_uri = $this->createUri('not-writable.txt');
 
     // Make the destination non-writable.
@@ -115,7 +115,13 @@ protected function doTransform($destination_uri, $configuration = []) {
       'http://drupal.org/favicon.ico',
       $destination_uri,
     ];
-    return $plugin->transform($value, $executable, $row, 'foo');
+
+    // Assert that number of stream resources in use is the same before and
+    // after the download.
+    $initial_count = count(get_resources('stream'));
+    $return = $plugin->transform($value, $executable, $row, 'foo');
+    $this->assertCount($initial_count, get_resources('stream'));
+    return $return;
   }
 
 }