Break up a circular dependency on shutdown

CHANGES

@@ -14,6 +14,12 @@ Relase date to be decided, codename to be chosen.
   URL rules specific to a given HTTP method.
 - Logger now only returns the debug log setting if it was not set
   explicitly.
+- Unregister a circular dependency between the WSGI environment and
+  the request object when shutting down the request.  This means that
+  environ ``werkzeug.request`` will be `None` after the response was
+  returned to the WSGI server but has the advantage that the garbage
+  collector is not needed on CPython to tear down the request unless
+  the user created circular dependencies themselves.
 
 Version 0.8.1
 -------------

flask/ctx.py

@@ -150,6 +150,10 @@ def pop(self):
         assert rv is self, 'Popped wrong request context.  (%r instead of %r)' \
             % (rv, self)
 
+        # get rid of circular dependencies at the end of the request
+        # so that we don't require the GC to be active.
+        rv.request.environ['werkzeug.request'] = None
+
     def __enter__(self):
         self.push()
         return self

flask/testsuite/regression.py

@@ -0,0 +1,83 @@
+# -*- coding: utf-8 -*-
+"""
+    flask.testsuite.regression
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+    Tests regressions.
+
+    :copyright: (c) 2011 by Armin Ronacher.
+    :license: BSD, see LICENSE for more details.
+"""
+
+from __future__ import with_statement
+
+import gc
+import sys
+import flask
+import threading
+import unittest
+from werkzeug.test import run_wsgi_app, create_environ
+from flask.testsuite import FlaskTestCase
+
+
+_gc_lock = threading.Lock()
+
+
+class _NoLeakAsserter(object):
+
+    def __init__(self, testcase):
+        self.testcase = testcase
+
+    def __enter__(self):
+        gc.disable()
+        _gc_lock.acquire()
+        loc = flask._request_ctx_stack._local
+
+        # Force Python to track this dictionary at all times.
+        # This is necessary since Python only starts tracking
+        # dicts if they contain mutable objects.  It's a horrible,
+        # horrible hack but makes this kinda testable.
+        loc.__storage__['FOOO'] = [1, 2, 3]
+
+        gc.collect()
+        self.old_objects = len(gc.get_objects())
+
+    def __exit__(self, exc_type, exc_value, tb):
+        if not hasattr(sys, 'getrefcount'):
+            gc.collect()
+        new_objects = len(gc.get_objects())
+        if new_objects > self.old_objects:
+            self.testcase.fail('Example code leaked')
+        _gc_lock.release()
+        gc.enable()
+
+
+class MemoryTestCase(FlaskTestCase):
+
+    def assert_no_leak(self):
+        return _NoLeakAsserter(self)
+
+    def test_memory_consumption(self):
+        app = flask.Flask(__name__)
+        @app.route('/')
+        def index():
+            return flask.render_template('simple_template.html', whiskey=42)
+
+        def fire():
+            with app.test_client() as c:
+                rv = c.get('/')
+                self.assert_equal(rv.status_code, 200)
+                self.assert_equal(rv.data, '<h1>42</h1>')
+
+        # Trigger caches
+        fire()
+
+        with self.assert_no_leak():
+            for x in xrange(10):
+                fire()
+
+
+def suite():
+    suite = unittest.TestSuite()
+    suite.addTest(unittest.makeSuite(MemoryTestCase))
+    return suite