Fixed #21740 -- Stopped using mutable default arguments in test client

Thanks Denver Coneybeare for the report and initial patch, and
Atala for another patch.

django/test/client.py

@@ -276,29 +276,29 @@ class RequestFactory(object):
             path = path.encode('utf-8').decode('iso-8859-1')
         return path
 
-    def get(self, path, data={}, secure=False, **extra):
+    def get(self, path, data=None, secure=False, **extra):
         "Construct a GET request."
 
         r = {
-            'QUERY_STRING': urlencode(data, doseq=True),
+            'QUERY_STRING': urlencode(data or {}, doseq=True),
         }
         r.update(extra)
         return self.generic('GET', path, secure=secure, **r)
 
-    def post(self, path, data={}, content_type=MULTIPART_CONTENT,
+    def post(self, path, data=None, content_type=MULTIPART_CONTENT,
              secure=False, **extra):
         "Construct a POST request."
 
-        post_data = self._encode_data(data, content_type)
+        post_data = self._encode_data(data or {}, content_type)
 
         return self.generic('POST', path, post_data, content_type,
                             secure=secure, **extra)
 
-    def head(self, path, data={}, secure=False, **extra):
+    def head(self, path, data=None, secure=False, **extra):
         "Construct a HEAD request."
 
         r = {
-            'QUERY_STRING': urlencode(data, doseq=True),
+            'QUERY_STRING': urlencode(data or {}, doseq=True),
         }
         r.update(extra)
         return self.generic('HEAD', path, secure=secure, **r)
@@ -460,7 +460,7 @@ class Client(RequestFactory):
             signals.template_rendered.disconnect(dispatch_uid=signal_uid)
             got_request_exception.disconnect(dispatch_uid="request-exception")
 
-    def get(self, path, data={}, follow=False, secure=False, **extra):
+    def get(self, path, data=None, follow=False, secure=False, **extra):
         """
         Requests a response from the server using GET.
         """
@@ -470,7 +470,7 @@ class Client(RequestFactory):
             response = self._handle_redirects(response, **extra)
         return response
 
-    def post(self, path, data={}, content_type=MULTIPART_CONTENT,
+    def post(self, path, data=None, content_type=MULTIPART_CONTENT,
              follow=False, secure=False, **extra):
         """
         Requests a response from the server using POST.
@@ -482,7 +482,7 @@ class Client(RequestFactory):
             response = self._handle_redirects(response, **extra)
         return response
 
-    def head(self, path, data={}, follow=False, secure=False, **extra):
+    def head(self, path, data=None, follow=False, secure=False, **extra):
         """
         Request a response from the server using HEAD.
         """

docs/topics/testing/tools.txt

@@ -129,7 +129,7 @@ Use the ``django.test.Client`` class to make requests.
     Once you have a ``Client`` instance, you can call any of the following
     methods:
 
-    .. method:: Client.get(path, data={}, follow=False, secure=False, **extra)
+    .. method:: Client.get(path, data=None, follow=False, secure=False, **extra)
 
         .. versionadded:: 1.7
 
@@ -192,7 +192,7 @@ Use the ``django.test.Client`` class to make requests.
         If you set ``secure`` to ``True`` the client will emulate an HTTPS
         request.
 
-    .. method:: Client.post(path, data={}, content_type=MULTIPART_CONTENT, follow=False, secure=False, **extra)
+    .. method:: Client.post(path, data=None, content_type=MULTIPART_CONTENT, follow=False, secure=False, **extra)
 
         Makes a POST request on the provided ``path`` and returns a
         ``Response`` object, which is documented below.
@@ -269,7 +269,7 @@ Use the ``django.test.Client`` class to make requests.
         If you set ``secure`` to ``True`` the client will emulate an HTTPS
         request.
 
-    .. method:: Client.head(path, data={}, follow=False, secure=False, **extra)
+    .. method:: Client.head(path, data=None, follow=False, secure=False, **extra)
 
         Makes a HEAD request on the provided ``path`` and returns a
         ``Response`` object. This method works just like :meth:`Client.get`,