Fixed #27175 -- Deprecated silencing exceptions from the {% include %} template tag.

Thanks Tim Graham for the review.

django/template/loader_tags.py

@@ -1,8 +1,10 @@
 import logging
 import posixpath
+import warnings
 from collections import defaultdict
 
 from django.utils import six
+from django.utils.deprecation import RemovedInDjango21Warning
 from django.utils.safestring import mark_safe
 
 from .base import (
@@ -208,10 +210,17 @@ class IncludeNode(Node):
                 return template.render(context.new(values))
             with context.push(**values):
                 return template.render(context)
-        except Exception:
+        except Exception as e:
             if context.template.engine.debug:
                 raise
             template_name = getattr(context, 'template_name', None) or 'unknown'
+            warnings.warn(
+                "Rendering {%% include '%s' %%} raised %s. In Django 2.1, "
+                "this exception will be raised rather than silenced and "
+                "rendered as an empty string." %
+                (template_name, e.__class__.__name__),
+                RemovedInDjango21Warning,
+            )
             logger.warning(
                 "Exception raised while rendering {%% include %%} for "
                 "template '%s'. Empty string rendered instead.",

docs/internals/deprecation.txt

@@ -33,6 +33,9 @@ details on these changes.
 * The ``host`` parameter of ``django.utils.http.is_safe_url()`` will be
   removed.
 
+* Silencing of exceptions raised while rendering the ``{% include %}`` template
+  tag will be removed.
+
 .. _deprecation-removed-in-2.0:
 
 2.0

docs/ref/templates/builtins.txt

@@ -731,6 +731,11 @@ is turned off, ``{% include %}`` logs a warning to the ``django.template``
 logger with the exception that happens while rendering the included template
 and returns an empty string.
 
+.. deprecated:: 1.11
+
+    Silencing exceptions raised while rendering the ``{% include %}`` template
+    tag is deprecated. In Django 2.1, the exception will be raised.
+
 .. note::
     The :ttag:`include` tag should be considered as an implementation of
     "render this subtemplate and include the HTML", not as "parse this

docs/releases/1.11.txt

@@ -528,3 +528,8 @@ Miscellaneous
 
 * The ``host`` parameter of ``django.utils.http.is_safe_url()`` is deprecated
   in favor of the new ``allowed_hosts`` parameter.
+
+* Silencing exceptions raised while rendering the
+  :ttag:`{% include %} <include>` template tag is deprecated as the behavior is
+  often more confusing than helpful. In Django 2.1, the exception will be
+  raised.

tests/template_tests/syntax_tests/test_include.py

@@ -1,7 +1,10 @@
+import warnings
+
 from django.template import (
     Context, Engine, TemplateDoesNotExist, TemplateSyntaxError,
 )
-from django.test import SimpleTestCase
+from django.test import SimpleTestCase, ignore_warnings
+from django.utils.deprecation import RemovedInDjango21Warning
 
 from ..utils import setup
 from .test_basic import basic_templates
@@ -41,9 +44,20 @@ class IncludeTagTests(SimpleTestCase):
             with self.assertRaises(TemplateDoesNotExist):
                 template.render(Context({}))
         else:
-            output = template.render(Context({}))
+            with warnings.catch_warnings(record=True) as warns:
+                warnings.simplefilter('always')
+                output = template.render(Context({}))
+
             self.assertEqual(output, "ab")
 
+            self.assertEqual(len(warns), 1)
+            self.assertEqual(
+                str(warns[0].message),
+                "Rendering {% include 'include04' %} raised "
+                "TemplateDoesNotExist. In Django 2.1, this exception will be "
+                "raised rather than silenced and rendered as an empty string.",
+            )
+
     @setup({
         'include 05': 'template with a space',
         'include06': '{% include "include 05"%}',
@@ -169,7 +183,8 @@ class IncludeTagTests(SimpleTestCase):
             with self.assertRaises(RuntimeError):
                 template.render(Context())
         else:
-            self.assertEqual(template.render(Context()), '')
+            with ignore_warnings(category=RemovedInDjango21Warning):
+                self.assertEqual(template.render(Context()), '')
 
     @setup({'include-error08': '{% include "include-fail2" %}'}, include_fail_templates)
     def test_include_error08(self):
@@ -179,7 +194,8 @@ class IncludeTagTests(SimpleTestCase):
             with self.assertRaises(TemplateSyntaxError):
                 template.render(Context())
         else:
-            self.assertEqual(template.render(Context()), '')
+            with ignore_warnings(category=RemovedInDjango21Warning):
+                self.assertEqual(template.render(Context()), '')
 
     @setup({'include-error09': '{% include failed_include %}'}, include_fail_templates)
     def test_include_error09(self):
@@ -190,7 +206,8 @@ class IncludeTagTests(SimpleTestCase):
             with self.assertRaises(RuntimeError):
                 template.render(context)
         else:
-            self.assertEqual(template.render(context), '')
+            with ignore_warnings(category=RemovedInDjango21Warning):
+                self.assertEqual(template.render(context), '')
 
     @setup({'include-error10': '{% include failed_include %}'}, include_fail_templates)
     def test_include_error10(self):
@@ -201,7 +218,8 @@ class IncludeTagTests(SimpleTestCase):
             with self.assertRaises(TemplateSyntaxError):
                 template.render(context)
         else:
-            self.assertEqual(template.render(context), '')
+            with ignore_warnings(category=RemovedInDjango21Warning):
+                self.assertEqual(template.render(context), '')
 
 
 class IncludeTests(SimpleTestCase):

tests/template_tests/test_logging.py

@@ -3,7 +3,8 @@ from __future__ import unicode_literals
 import logging
 
 from django.template import Context, Engine, Variable, VariableDoesNotExist
-from django.test import SimpleTestCase
+from django.test import SimpleTestCase, ignore_warnings
+from django.utils.deprecation import RemovedInDjango21Warning
 
 
 class TestHandler(logging.Handler):
@@ -104,7 +105,8 @@ class IncludeNodeLoggingTests(BaseTemplateLoggingTestCase):
     def test_logs_exceptions_during_rendering_with_debug_disabled(self):
         template = self.engine.from_string('{% include "child" %}')
         template.name = 'template_name'
-        self.assertEqual(template.render(self.ctx), '')
+        with ignore_warnings(category=RemovedInDjango21Warning):
+            self.assertEqual(template.render(self.ctx), '')
         self.assertEqual(
             self.test_handler.log_record.getMessage(),
             "Exception raised while rendering {% include %} for template "
@@ -115,7 +117,8 @@ class IncludeNodeLoggingTests(BaseTemplateLoggingTestCase):
 
     def test_logs_exceptions_during_rendering_with_no_template_name(self):
         template = self.engine.from_string('{% include "child" %}')
-        self.assertEqual(template.render(self.ctx), '')
+        with ignore_warnings(category=RemovedInDjango21Warning):
+            self.assertEqual(template.render(self.ctx), '')
         self.assertEqual(
             self.test_handler.log_record.getMessage(),
             "Exception raised while rendering {% include %} for template "