Converted sql_queries into a lazily evaluated list.

Fixed #23364. Thanks Markush2010 for the report.

django/core/context_processors.py

@@ -35,12 +35,16 @@ def csrf(request):
 
 
 def debug(request):
-    "Returns context variables helpful for debugging."
+    """
+    Returns context variables helpful for debugging.
+    """
     context_extras = {}
     if settings.DEBUG and request.META.get('REMOTE_ADDR') in settings.INTERNAL_IPS:
         context_extras['debug'] = True
         from django.db import connection
-        context_extras['sql_queries'] = connection.queries
+        # Return a lazy reference that computes connection.queries on access,
+        # to ensure it contains queries triggered after this function runs.
+        context_extras['sql_queries'] = lazy(lambda: connection.queries, list)
     return context_extras
 
 

docs/ref/templates/api.txt

@@ -555,7 +555,8 @@ If :setting:`TEMPLATE_CONTEXT_PROCESSORS` contains this processor, every
   you're in :setting:`DEBUG` mode.
 * ``sql_queries`` -- A list of ``{'sql': ..., 'time': ...}`` dictionaries,
   representing every SQL query that has happened so far during the request
-  and how long it took. The list is in order by query.
+  and how long it took. The list is in order by query and lazily generated
+  on access.
 
 django.core.context_processors.i18n
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

tests/context_processors/models.py

@@ -0,0 +1,5 @@
+from django.db import models
+
+
+class DebugObject(models.Model):
+    pass

tests/context_processors/templates/context_processors/debug.html

@@ -0,0 +1,15 @@
+{% if debug == True %}
+
+Have debug
+
+First query list: {{ sql_queries|length }}
+
+{% for obj in debug_objects.all %}{{ obj }}{% endfor %}
+
+Second query list: {{ sql_queries|length }}
+
+{% for obj in debug_objects.all %}{{ obj }}{% endfor %}
+
+Third query list: {{ sql_queries|length }}
+
+{% endif %}

tests/context_processors/tests.py

@@ -33,3 +33,33 @@ class RequestContextProcessorTests(TestCase):
         self.assertContains(response, url)
         response = self.client.post(url, {'path': '/blah/'})
         self.assertContains(response, url)
+
+
+@override_settings(ROOT_URLCONF='context_processors.urls', DEBUG=True, INTERNAL_IPS=('127.0.0.1',))
+class DebugContextProcessorTests(TestCase):
+    """
+    Tests for the ``django.core.context_processors.debug`` processor.
+    """
+
+    def test_debug(self):
+        url = '/debug/'
+        # We should have the debug flag in the template.
+        response = self.client.get(url)
+        self.assertContains(response, 'Have debug')
+
+        # And now we should not
+        with override_settings(DEBUG=False):
+            response = self.client.get(url)
+            self.assertNotContains(response, 'Have debug')
+
+    def test_sql_queries(self):
+        """
+        Test whether sql_queries represents the actual amount
+        of queries executed. (#23364)
+        """
+        url = '/debug/'
+        response = self.client.get(url)
+        self.assertContains(response, 'First query list: 0')
+        self.assertContains(response, 'Second query list: 1')
+        # Check we have not actually memoized connection.queries
+        self.assertContains(response, 'Third query list: 2')

tests/context_processors/urls.py

@@ -5,4 +5,5 @@ from . import views
 
 urlpatterns = [
     url(r'^request_attrs/$', views.request_processor),
+    url(r'^debug/$', views.debug_processor),
 ]

tests/context_processors/views.py

@@ -2,7 +2,18 @@ from django.core import context_processors
 from django.shortcuts import render_to_response
 from django.template.context import RequestContext
 
+from .models import DebugObject
+
 
 def request_processor(request):
-    return render_to_response('context_processors/request_attrs.html',
+    return render_to_response(
+        'context_processors/request_attrs.html',
         RequestContext(request, {}, processors=[context_processors.request]))
+
+
+def debug_processor(request):
+    return render_to_response(
+        'context_processors/debug.html',
+        RequestContext(request, {
+            'debug_objects': DebugObject.objects,
+        }, processors=[context_processors.debug]))