Fixed django#6262 -- Added a cached template loader, and modified exi…

…sting template loaders and tag to be cacheable. Thanks to Mike Malone for the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@11862 bcc190cf-cafb-0310-a4f2-bffc1f526a37

AUTHORS

@@ -288,6 +288,7 @@ answer newbie questions, and generally made Django that much better:
     Martin Mahner <http://www.mahner.org/>
     Matt McClanahan <http://mmcc.cx/>
     Frantisek Malina <vizualbod@vizualbod.com>
+    Mike Malone <mjmalone@gmail.com>
     Martin Maney <http://www.chipy.org/Martin_Maney>
     masonsimon+django@gmail.com
     Manuzhai

django/conf/global_settings.py

@@ -158,9 +158,9 @@
 # See the comments in django/core/template/loader.py for interface
 # documentation.
 TEMPLATE_LOADERS = (
-    'django.template.loaders.filesystem.load_template_source',
-    'django.template.loaders.app_directories.load_template_source',
-#     'django.template.loaders.eggs.load_template_source',
+    'django.template.loaders.filesystem.Loader',
+    'django.template.loaders.app_directories.Loader',
+#     'django.template.loaders.eggs.Loader',
 )
 
 # List of processors used by RequestContext to populate the context.

django/conf/project_template/settings.py

@@ -52,9 +52,9 @@
 
 # List of callables that know how to import templates from various sources.
 TEMPLATE_LOADERS = (
-    'django.template.loaders.filesystem.load_template_source',
-    'django.template.loaders.app_directories.load_template_source',
-#     'django.template.loaders.eggs.load_template_source',
+    'django.template.loaders.filesystem.Loader',
+    'django.template.loaders.app_directories.Loader',
+#     'django.template.loaders.eggs.Loader',
 )
 
 MIDDLEWARE_CLASSES = (

django/template/__init__.py

@@ -173,9 +173,16 @@ def __iter__(self):
             for subnode in node:
                 yield subnode
 
+    def _render(self, context):
+        return self.nodelist.render(context)
+
     def render(self, context):
         "Display stage -- can be called many times"
-        return self.nodelist.render(context)
+        context.render_context.push()
+        try:
+            return self._render(context)
+        finally:
+            context.render_context.pop()
 
 def compile_string(template_string, origin):
     "Compiles template_string into NodeList ready for rendering"

django/template/context.py

@@ -12,67 +12,101 @@ class ContextPopException(Exception):
     "pop() has been called more times than push()"
     pass
 
-class Context(object):
-    "A stack container for variable context"
-    def __init__(self, dict_=None, autoescape=True, current_app=None):
+class BaseContext(object):
+    def __init__(self, dict_=None):
         dict_ = dict_ or {}
         self.dicts = [dict_]
-        self.autoescape = autoescape
-        self.current_app = current_app
 
     def __repr__(self):
         return repr(self.dicts)
 
     def __iter__(self):
-        for d in self.dicts:
+        for d in reversed(self.dicts):
             yield d
 
     def push(self):
         d = {}
-        self.dicts = [d] + self.dicts
+        self.dicts.append(d)
         return d
 
     def pop(self):
         if len(self.dicts) == 1:
             raise ContextPopException
-        return self.dicts.pop(0)
+        return self.dicts.pop()
 
     def __setitem__(self, key, value):
         "Set a variable in the current context"
-        self.dicts[0][key] = value
+        self.dicts[-1][key] = value
 
     def __getitem__(self, key):
         "Get a variable's value, starting at the current context and going upward"
-        for d in self.dicts:
+        for d in reversed(self.dicts):
             if key in d:
                 return d[key]
         raise KeyError(key)
 
     def __delitem__(self, key):
         "Delete a variable from the current context"
-        del self.dicts[0][key]
+        del self.dicts[-1][key]
 
     def has_key(self, key):
         for d in self.dicts:
             if key in d:
                 return True
         return False
 
-    __contains__ = has_key
+    def __contains__(self, key):
+        return self.has_key(key)
 
     def get(self, key, otherwise=None):
-        for d in self.dicts:
+        for d in reversed(self.dicts):
             if key in d:
                 return d[key]
         return otherwise
 
+class Context(BaseContext):
+    "A stack container for variable context"
+    def __init__(self, dict_=None, autoescape=True, current_app=None):
+        self.autoescape = autoescape
+        self.current_app = current_app
+        self.render_context = RenderContext()
+        super(Context, self).__init__(dict_)
+
     def update(self, other_dict):
         "Like dict.update(). Pushes an entire dictionary's keys and values onto the context."
         if not hasattr(other_dict, '__getitem__'):
             raise TypeError('other_dict must be a mapping (dictionary-like) object.')
-        self.dicts = [other_dict] + self.dicts
+        self.dicts.append(other_dict)
         return other_dict
 
+class RenderContext(BaseContext):
+    """
+    A stack container for storing Template state.
+
+    RenderContext simplifies the implementation of template Nodes by providing a
+    safe place to store state between invocations of a node's `render` method.
+
+    The RenderContext also provides scoping rules that are more sensible for
+    'template local' variables. The render context stack is pushed before each
+    template is rendered, creating a fresh scope with nothing in it. Name
+    resolution fails if a variable is not found at the top of the RequestContext
+    stack. Thus, variables are local to a specific template and don't affect the
+    rendering of other templates as they would if they were stored in the normal
+    template context.
+    """
+    def __iter__(self):
+        for d in self.dicts[-1]:
+            yield d
+
+    def has_key(self, key):
+        return key in self.dicts[-1]
+
+    def get(self, key, otherwise=None):
+        d = self.dicts[-1]
+        if key in d:
+            return d[key]
+        return otherwise
+
 # This is a function rather than module-level procedural code because we only
 # want it to execute if somebody uses RequestContext.
 def get_standard_processors():

django/template/defaulttags.py

@@ -57,11 +57,14 @@ def render(self, context):
 
 class CycleNode(Node):
     def __init__(self, cyclevars, variable_name=None):
-        self.cycle_iter = itertools_cycle(cyclevars)
+        self.cyclevars = cyclevars
         self.variable_name = variable_name
 
     def render(self, context):
-        value = self.cycle_iter.next().resolve(context)
+        if self not in context.render_context:
+            context.render_context[self] = itertools_cycle(self.cyclevars)
+        cycle_iter = context.render_context[self]
+        value = cycle_iter.next().resolve(context)
         if self.variable_name:
             context[self.variable_name] = value
         return value

django/template/loader.py

@@ -27,6 +27,36 @@
 
 template_source_loaders = None
 
+class BaseLoader(object):
+    is_usable = False
+
+    def __init__(self, *args, **kwargs):
+        pass
+
+    def __call__(self, template_name, template_dirs=None):
+        return self.load_template(template_name, template_dirs)
+
+    def load_template(self, template_name, template_dirs=None):
+        source, origin = self.load_template_source(template_name, template_dirs)
+        template = get_template_from_string(source, name=template_name)
+        return template, origin
+
+    def load_template_source(self, template_name, template_dirs=None):
+        """
+        Returns a tuple containing the source and origin for the given template
+        name.
+
+        """
+        raise NotImplementedError
+
+    def reset(self):
+        """
+        Resets any state maintained by the loader instance (e.g., cached
+        templates or cached loader modules).
+
+        """
+        pass
+
 class LoaderOrigin(Origin):
     def __init__(self, display_name, loader, name, dirs):
         super(LoaderOrigin, self).__init__(display_name)
@@ -41,29 +71,50 @@ def make_origin(display_name, loader, name, dirs):
     else:
         return None
 
-def find_template_source(name, dirs=None):
+def find_template_loader(loader):
+    if hasattr(loader, '__iter__'):
+        loader, args = loader[0], loader[1:]
+    else:
+        args = []
+    if isinstance(loader, basestring):
+        module, attr = loader.rsplit('.', 1)
+        try:
+            mod = import_module(module)
+        except ImportError:
+            raise ImproperlyConfigured('Error importing template source loader %s: "%s"' % (loader, e))
+        try:
+            TemplateLoader = getattr(mod, attr)
+        except AttributeError, e:
+            raise ImproperlyConfigured('Error importing template source loader %s: "%s"' % (loader, e))
+
+        if hasattr(TemplateLoader, 'load_template_source'):
+            func = TemplateLoader(*args)
+        else:
+            # Try loading module the old way - string is full path to callable
+            if args:
+                raise ImproperlyConfigured("Error importing template source loader %s - can't pass arguments to function-based loader." % loader)
+            func = TemplateLoader
+
+        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." % loader)
+            return None
+        else:
+            return func
+    else:
+        raise ImproperlyConfigured('Loader does not define a "load_template" callable template source loader')
+
+def find_template(name, dirs=None):
     # Calculate template_source_loaders the first time the function is executed
     # because putting this logic in the module-level namespace may cause
     # circular import errors. See Django ticket #1292.
     global template_source_loaders
     if template_source_loaders is None:
         loaders = []
-        for path in settings.TEMPLATE_LOADERS:
-            i = path.rfind('.')
-            module, attr = path[:i], path[i+1:]
-            try:
-                mod = import_module(module)
-            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:
-                loaders.append(func)
+        for loader_name in settings.TEMPLATE_LOADERS:
+            loader = find_template_loader(loader_name)
+            if loader is not None:
+                loaders.append(loader)
         template_source_loaders = tuple(loaders)
     for loader in template_source_loaders:
         try:
@@ -73,13 +124,27 @@ def find_template_source(name, dirs=None):
             pass
     raise TemplateDoesNotExist, name
 
+def find_template_source(name, dirs=None):
+    # For backward compatibility
+    import warnings
+    warnings.warn(
+        "`django.template.loaders.find_template_source` is deprecated; use `django.template.loaders.find_template` instead.",
+        PendingDeprecationWarning
+    )
+    template, origin = find_template(name, dirs)
+    if hasattr(template, 'render'):
+        raise Exception("Found a compiled template that is incompatible with the deprecated `django.template.loaders.find_template_source` function.")
+    return template, origin
+
 def get_template(template_name):
     """
     Returns a compiled Template object for the given template name,
     handling template inheritance recursively.
     """
-    source, origin = find_template_source(template_name)
-    template = get_template_from_string(source, origin, template_name)
+    template, origin = find_template(template_name)
+    if not hasattr(template, 'render'):
+        # template needs to be compiled
+        template = get_template_from_string(template, origin, template_name)
     return template
 
 def get_template_from_string(source, origin=None, name=None):