MERGED MAGIC-REMOVAL BRANCH TO TRUNK. This change is highly backwards-incompatible. Please read http://code.djangoproject.com/wiki/RemovingTheMagic for upgrade instructions.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@2809 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/template/context.py

@@ -0,0 +1,97 @@
+from django.conf import settings
+from django.core.exceptions import ImproperlyConfigured
+
+_standard_context_processors = None
+
+class ContextPopException(Exception):
+    "pop() has been called more times than push()"
+    pass
+
+class Context:
+    "A stack container for variable context"
+    def __init__(self, dict_=None):
+        dict_ = dict_ or {}
+        self.dicts = [dict_]
+
+    def __repr__(self):
+        return repr(self.dicts)
+
+    def __iter__(self):
+        for d in self.dicts:
+            yield d
+
+    def push(self):
+        self.dicts = [{}] + self.dicts
+
+    def pop(self):
+        if len(self.dicts) == 1:
+            raise ContextPopException
+        del self.dicts[0]
+
+    def __setitem__(self, key, value):
+        "Set a variable in the current context"
+        self.dicts[0][key] = value
+
+    def __getitem__(self, key):
+        "Get a variable's value, starting at the current context and going upward"
+        for d in self.dicts:
+            if d.has_key(key):
+                return d[key]
+        return settings.TEMPLATE_STRING_IF_INVALID
+
+    def __delitem__(self, key):
+        "Delete a variable from the current context"
+        del self.dicts[0][key]
+
+    def has_key(self, key):
+        for d in self.dicts:
+            if d.has_key(key):
+                return True
+        return False
+
+    def get(self, key, otherwise):
+        for d in self.dicts:
+            if d.has_key(key):
+                return d[key]
+        return otherwise
+
+    def update(self, other_dict):
+        "Like dict.update(). Pushes an entire dictionary's keys and values onto the context."
+        self.dicts = [other_dict] + self.dicts
+
+# 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():
+    global _standard_context_processors
+    if _standard_context_processors is None:
+        processors = []
+        for path in settings.TEMPLATE_CONTEXT_PROCESSORS:
+            i = path.rfind('.')
+            module, attr = path[:i], path[i+1:]
+            try:
+                mod = __import__(module, '', '', [attr])
+            except ImportError, e:
+                raise ImproperlyConfigured, 'Error importing request processor module %s: "%s"' % (module, e)
+            try:
+                func = getattr(mod, attr)
+            except AttributeError:
+                raise ImproperlyConfigured, 'Module "%s" does not define a "%s" callable request processor' % (module, attr)
+            processors.append(func)
+        _standard_context_processors = tuple(processors)
+    return _standard_context_processors
+
+class RequestContext(Context):
+    """
+    This subclass of template.Context automatically populates itself using
+    the processors defined in TEMPLATE_CONTEXT_PROCESSORS.
+    Additional processors can be specified as a list of callables
+    using the "processors" keyword argument.
+    """
+    def __init__(self, request, dict=None, processors=None):
+        Context.__init__(self, dict)
+        if processors is None:
+            processors = ()
+        else:
+            processors = tuple(processors)
+        for processor in get_standard_processors() + processors:
+            self.update(processor(request))