Do not close the underlying file from compression plugins (#6239)

docs/topics/feed-exports.rst

@@ -390,7 +390,13 @@ Each plugin is a class that must implement the following methods:
 
 .. method:: close(self)
 
-    Close the target file object.
+    Clean up the plugin.
+
+    For example, you might want to close a file wrapper that you might have
+    used to compress data written into the file received in the ``__init__``
+    method.
+
+    .. warning:: Do not close the file from the ``__init__`` method.
 
 To pass a parameter to your plugin, use :ref:`feed options <feed-options>`. You
 can then access those parameters from the ``__init__`` method of your plugin.

scrapy/extensions/postprocessing.py

@@ -42,7 +42,6 @@ def write(self, data: bytes) -> int:
 
     def close(self) -> None:
         self.gzipfile.close()
-        self.file.close()
 
 
 class Bz2Plugin:
@@ -69,7 +68,6 @@ def write(self, data: bytes) -> int:
 
     def close(self) -> None:
         self.bz2file.close()
-        self.file.close()
 
 
 class LZMAPlugin:
@@ -111,7 +109,6 @@ def write(self, data: bytes) -> int:
 
     def close(self) -> None:
         self.lzmafile.close()
-        self.file.close()
 
 
 # io.IOBase is subclassed here, so that exporters can use the PostProcessingManager

tests/test_feedexport.py

@@ -1731,6 +1731,7 @@ def open(self, spider):
 
             def store(self, file):
                 Storage.store_file = file
+                Storage.file_was_closed = file.closed
                 file.close()
 
         settings = {
@@ -1746,6 +1747,7 @@ def store(self, file):
         }
         yield self.exported_no_data(settings)
         self.assertIs(Storage.open_file, Storage.store_file)
+        self.assertFalse(Storage.file_was_closed)
 
 
 class FeedPostProcessedExportsTest(FeedExportTestBase):