Fixed #13334: Restored ability to load template tags from eggs. Again thanks Ramiro and metzen for pointers on how to find out if a module loaded from an egg has a particular submodule, and Russ for review.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12986 bcc190cf-cafb-0310-a4f2-bffc1f526a37

3 files changed, 53 insertions, 10 deletions

diff --git a/django/template/__init__.py b/django/template/__init__.py
index 00949d6e59..c3167861fd 100644
--- a/django/template/__init__.py
+++ b/django/template/__init__.py
@@ -63,6 +63,7 @@ from django.utils.translation import ugettext as _
 from django.utils.safestring import SafeData, EscapeData, mark_safe, mark_for_escaping
 from django.utils.formats import localize
 from django.utils.html import escape
+from django.utils.module_loading import module_has_submodule
 
 __all__ = ('Template', 'Context', 'RequestContext', 'compile_string')
 
@@ -980,19 +981,18 @@ def import_library(taglib_module):
     Verifies that the library contains a 'register' attribute, and
     returns that attribute as the representation of the library
     """
-    # We need to be able to tell the difference between a tag library that
-    # doesn't exist, and a tag library with errors in it.
-    # find_module() finds, but doesn't actually load the module requested.
-    # If it raises ImportError, it means the module doesn't exist.
-    # If you then use load_module(), any ImportError is guaranteed to be
-    # an actual import problem with the module.
     app_path, taglib = taglib_module.rsplit('.',1)
     app_module = import_module(app_path)
     try:
-        imp.find_module(taglib, app_module.__path__)
-    except ImportError,e:
-        return None
-    mod = import_module(taglib_module)
+        mod = import_module(taglib_module)
+    except ImportError, e:
+        # If the ImportError is because the taglib submodule does not exist, that's not
+        # an error that should be raised. If the submodule exists and raised an ImportError
+        # on the attempt to load it, that we want to raise.
+        if not module_has_submodule(app_module, taglib):
+            return None
+        else:
+            raise InvalidTemplateLibrary("ImportError raised loading %s: %s" % (taglib_module, e))
     try:
         return mod.register
     except AttributeError:
diff --git a/tests/regressiontests/templates/eggs/tagsegg.egg b/tests/regressiontests/templates/eggs/tagsegg.egg
new file mode 100755
index 0000000000..3941914b81
--- /dev/null
+++ b/tests/regressiontests/templates/eggs/tagsegg.egg
diff --git a/tests/regressiontests/templates/tests.py b/tests/regressiontests/templates/tests.py
index 372d2ab1c2..33d0650c7c 100644
--- a/tests/regressiontests/templates/tests.py
+++ b/tests/regressiontests/templates/tests.py
@@ -1287,5 +1287,48 @@ class Templates(unittest.TestCase):
             'autoescape-filtertag01': ("{{ first }}{% filter safe %}{{ first }} x<y{% endfilter %}", {"first": "<a>"}, template.TemplateSyntaxError),
         }
 
+
+class TemplateTagLoading(unittest.TestCase):
+
+    def setUp(self):
+        self.old_path = sys.path
+        self.old_apps = settings.INSTALLED_APPS
+        self.egg_dir = '%s/eggs' % os.path.dirname(__file__)
+        self.old_tag_modules = template.templatetags_modules
+        template.templatetags_modules = []
+
+    def tearDown(self):
+        settings.INSTALLED_APPS = self.old_apps
+        sys.path = self.old_path
+        template.templatetags_modules = self.old_tag_modules
+
+    def test_load_error(self):
+        ttext = "{% load broken_tag %}"
+        self.assertRaises(template.TemplateSyntaxError, template.Template, ttext)
+        try:
+            template.Template(ttext)
+        except template.TemplateSyntaxError, e:
+            self.assertTrue('ImportError' in e.args[0])
+            self.assertTrue('Xtemplate' in e.args[0])
+
+    def test_load_error_egg(self):
+        ttext = "{% load broken_egg %}"
+        egg_name = '%s/tagsegg.egg' % self.egg_dir
+        sys.path.append(egg_name)
+        settings.INSTALLED_APPS = ('tagsegg',)
+        self.assertRaises(template.TemplateSyntaxError, template.Template, ttext)
+        try:
+            template.Template(ttext)
+        except template.TemplateSyntaxError, e:
+            self.assertTrue('ImportError' in e.args[0])
+            self.assertTrue('Xtemplate' in e.args[0])
+
+    def test_load_working_egg(self):
+        ttext = "{% load working_egg %}"
+        egg_name = '%s/tagsegg.egg' % self.egg_dir
+        sys.path.append(egg_name)
+        settings.INSTALLED_APPS = ('tagsegg',)
+        t = template.Template(ttext)
+
 if __name__ == "__main__":
     unittest.main()