Fixed #582 -- Added support for loading templates from Python eggs, and a TEMPLATE_LOADERS setting, which defines which loaders to use. Thanks, Sune

git-svn-id: http://code.djangoproject.com/svn/django/trunk@870 bcc190cf-cafb-0310-a4f2-bffc1f526a37

4 files changed, 79 insertions, 2 deletions

diff --git a/django/conf/global_settings.py b/django/conf/global_settings.py
index ea2fc440de..dde5612038 100644
--- a/django/conf/global_settings.py
+++ b/django/conf/global_settings.py
@@ -61,6 +61,14 @@ TEMPLATE_DIRS = ()
 # Extension on all templates.
 TEMPLATE_FILE_EXTENSION = '.html'
 
+# List of callables that know how to import templates from various sources.
+# See the comments in django/core/template/loader.py for interface
+# documentation.
+TEMPLATE_LOADERS = (
+    'django.core.template.loaders.filesystem.load_template_source',
+#     'django.core.template.loaders.eggs.load_template_source',
+)
+
 # URL prefix for admin media -- CSS, JavaScript and images. Make sure to use a
 # trailing slash.
 # Examples: "http://foo.com/media/", "/media/".
diff --git a/django/core/template/loader.py b/django/core/template/loader.py
index 65a6c735b3..067b3fcfb8 100644
--- a/django/core/template/loader.py
+++ b/django/core/template/loader.py
@@ -1,7 +1,50 @@
-"Wrapper for loading templates from storage of some sort (e.g. files or db)"
+# Wrapper for loading templates from storage of some sort (e.g. filesystem, database).
+#
+# This uses the TEMPLATE_LOADERS setting, which is a list of loaders to use.
+# Each loader is expected to have this interface:
+#
+#    callable(name, dirs=[])
+#
+# name is the template name.
+# dirs is an optional list of directories to search instead of TEMPLATE_DIRS.
+#
+# Each loader should have an "is_usable" attribute set. This is a boolean that
+# specifies whether the loader can be used in this Python installation. Each
+# loader is responsible for setting this when it's initialized.
+#
+# For example, the eggs loader (which is capable of loading templates from
+# Python eggs) sets is_usable to False if the "pkg_resources" module isn't
+# installed, because pkg_resources is necessary to read eggs.
 
+from django.core.exceptions import ImproperlyConfigured
 from django.core.template import Template, Context, Node, TemplateDoesNotExist, TemplateSyntaxError, resolve_variable_with_filters, register_tag
-from django.core.template.loaders.filesystem import load_template_source
+from django.conf.settings import TEMPLATE_LOADERS
+
+template_source_loaders = []
+for path in TEMPLATE_LOADERS:
+    i = path.rfind('.')
+    module, attr = path[:i], path[i+1:]
+    try:
+        mod = __import__(module, globals(), locals(), [attr])
+    except ImportError, e:
+        raise ImproperlyConfigured, 'Error importing template source loader %s: "%s"' % (module, e)
+    try:
+        func = getattr(mod, attr)
+    except AttributeError:
+        raise ImproperlyConfigured, 'Module "%s" does not define a "%s" callable template source loader' % (module, attr)
+    if not func.is_usable:
+        import warnings
+        warnings.warn("Your TEMPLATE_LOADERS setting includes %r, but your Python installation doesn't support that type of template loading. Consider removing that line from TEMPLATE_LOADERS." % path)
+    else:
+        template_source_loaders.append(func)
+
+def load_template_source(name, dirs=None):
+    for loader in template_source_loaders:
+        try:
+            return loader(name, dirs)
+        except template.TemplateDoesNotExist:
+            pass
+    raise template.TemplateDoesNotExist, name
 
 class ExtendsError(Exception):
     pass
diff --git a/django/core/template/loaders/eggs.py b/django/core/template/loaders/eggs.py
new file mode 100644
index 0000000000..b1e221ee1c
--- /dev/null
+++ b/django/core/template/loaders/eggs.py
@@ -0,0 +1,25 @@
+# Wrapper for loading templates from eggs via pkg_resources.resource_string.
+
+try:
+    from pkg_resources import resource_string
+except ImportError:
+    resource_string = None
+
+from django.core.template import TemplateDoesNotExist
+from django.conf.settings import INSTALLED_APPS, TEMPLATE_FILE_EXTENSION
+
+def load_template_source(name, dirs=None):
+    """
+    Loads templates from Python eggs via pkg_resource.resource_string.
+
+    For every installed app, it tries to get the resource (app, name).
+    """
+    if resource_string is not None:
+        pkg_name = 'templates/' + name + TEMPLATE_FILE_EXTENSION
+        for app in INSTALLED_APPS:
+            try:
+                return resource_string(app, pkg_name)
+            except:
+                pass
+    raise TemplateDoesNotExist, name
+load_template_source.is_usable = resource_string is not None
diff --git a/django/core/template/loaders/filesystem.py b/django/core/template/loaders/filesystem.py
index 849f62b94e..1d42c6d841 100644
--- a/django/core/template/loaders/filesystem.py
+++ b/django/core/template/loaders/filesystem.py
@@ -19,3 +19,4 @@ def load_template_source(template_name, template_dirs=None):
     else:
         error_msg = "Your TEMPLATE_DIRS settings is empty. Change it to point to at least one template directory."
     raise TemplateDoesNotExist, error_msg
+load_template_source.is_usable = True