Fix I/O operation on closed file error in Response classes

examples/response_closed.py

@@ -0,0 +1,42 @@
+#!/usr/bin/env python3
+"""Example demonstrating Response with closed buffer scenario."""
+from sys import path as python_path
+
+import os
+
+EXAMPLES_PATH = os.path.dirname(__file__)
+python_path.insert(0, os.path.abspath(
+    os.path.join(EXAMPLES_PATH, os.path.pardir)))
+
+# pylint: disable=wrong-import-position
+from poorwsgi import Application  # noqa
+from poorwsgi.response import Response  # noqa
+
+app = application = Application("response_closed")
+
+
+@app.route("/test")
+def handler(_):
+    """Simple test handler that returns a Response."""
+    res = Response("Test data")
+    # After response is sent, the buffer will be closed by WSGI server
+    # Accessing res.data after that should be handled gracefully
+    return res
+
+
+@app.route("/test-after-response")
+def handler_after_response(_):
+    """Handler that tries to access response data after creation."""
+    res = Response("Test data")
+    # Try to access data property immediately (should work)
+    data = res.data
+    # Just verify it works, don't log
+    assert data == b"Test data"
+    return res
+
+
+if __name__ == "__main__":
+    from wsgiref.simple_server import make_server
+    print("Starting server on http://localhost:8080")
+    httpd = make_server("localhost", 8080, app)
+    httpd.serve_forever()

poorwsgi/response.py

@@ -356,6 +356,10 @@ def __init__(self, data: Union[str, bytes] = b'',
 
     @property
     def data(self):
+        if self.__buffer.closed:  # pylint: disable=using-constant-test
+            log.warning("Attempt to access data from closed buffer. "
+                        "Response has likely been sent already.")
+            return b''
         self.__buffer.seek(0)
         return self.__buffer.read()
 
@@ -367,6 +371,10 @@ def write(self, data: Union[str, bytes]):
         self.__buffer.write(data)
 
     def __end_of_response__(self):
+        if self.__buffer.closed:  # pylint: disable=using-constant-test
+            log.error("Buffer is closed in __end_of_response__. "
+                      "This should not happen.")
+            return IBytesIO(b'')
         self.__buffer.seek(self._start)
         if self._end:
             return IBytesIO(self.__buffer.read(self._end - self._start + 1))
@@ -502,6 +510,10 @@ def data(self):
 
         This property works only if file_obj is seekable.
         """
+        if self.__file.closed:
+            log.warning("Attempt to access data from closed file. "
+                        "Response has likely been sent already.")
+            return b''
         if self.__file.seekable():
             self.__file.seek(self.__pos)
             return self.__file.read()
@@ -515,6 +527,10 @@ def __end_of_response__(self):
         This method was called from Application object at the end of request
         for returning right value to wsgi server.
         """
+        if self.__file.closed:
+            log.error("File is closed in __end_of_response__. "
+                      "This should not happen.")
+            return IBytesIO(b'')
         if self.__file.seekable():
             self.__file.seek(self._start)
             if self._end:

tests_integrity/test_response_closed.py

@@ -0,0 +1,33 @@
+"""Integrity test for closed buffer handling."""
+from os.path import dirname, join, pardir
+
+from pytest import fixture
+
+from .support import check_url, start_server
+
+# pylint: disable=missing-function-docstring
+# pylint: disable=redefined-outer-name
+
+
+@fixture(scope="module")
+def url(request):
+    """URL (server fixture in fact)."""
+    process = start_server(
+        request,
+        join(dirname(__file__), pardir, 'examples/response_closed.py'))
+
+    yield "http://localhost:8080"  # server is running
+    process.kill()
+    process.wait()
+
+
+class TestResponseClosed:
+    """Test for Response with closed buffer handling."""
+
+    def test_simple_response(self, url):
+        """Test that a simple response works normally."""
+        check_url(url+"/test")
+
+    def test_response_data_access(self, url):
+        """Test that accessing data property before sending works."""
+        check_url(url+"/test-after-response")