web/lib/django/template/loader.py
changeset 38 77b6da96e6f1
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/web/lib/django/template/loader.py	Wed Jun 02 18:57:35 2010 +0200
@@ -0,0 +1,198 @@
+# 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.
+#
+# The loader should return a tuple of (template_source, path). The path returned
+# might be shown to the user for debugging purposes, so it should identify where
+# the template was loaded from.
+#
+# A loader may return an already-compiled template instead of the actual
+# template source. In that case the path returned should be None, since the
+# path information is associated with the template during the compilation,
+# which has already been done.
+#
+# 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.template import Origin, Template, Context, TemplateDoesNotExist, add_to_builtins
+from django.utils.importlib import import_module
+from django.conf import settings
+
+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, display_name = self.load_template_source(template_name, template_dirs)
+        origin = make_origin(display_name, self.load_template_source, template_name, template_dirs)
+        try:
+            template = get_template_from_string(source, origin, template_name)
+            return template, None
+        except TemplateDoesNotExist:
+            # If compiling the template we found raises TemplateDoesNotExist, back off to
+            # returning the source and display name for the template we were asked to load.
+            # This allows for correct identification (later) of the actual template that does
+            # not exist.
+            return source, display_name
+
+    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)
+        self.loader, self.loadname, self.dirs = loader, name, dirs
+
+    def reload(self):
+        return self.loader(self.loadname, self.dirs)[0]
+
+def make_origin(display_name, loader, name, dirs):
+    if settings.TEMPLATE_DEBUG and display_name:
+        return LoaderOrigin(display_name, loader, name, dirs)
+    else:
+        return None
+
+def find_template_loader(loader):
+    if isinstance(loader, (tuple, list)):
+        loader, args = loader[0], loader[1:]
+    else:
+        args = []
+    if isinstance(loader, basestring):
+        module, attr = loader.rsplit('.', 1)
+        try:
+            mod = import_module(module)
+        except ImportError, e:
+            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 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:
+            source, display_name = loader(name, dirs)
+            return (source, make_origin(display_name, loader, name, dirs))
+        except TemplateDoesNotExist:
+            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.
+    """
+    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):
+    """
+    Returns a compiled Template object for the given template code,
+    handling template inheritance recursively.
+    """
+    return Template(source, origin, name)
+
+def render_to_string(template_name, dictionary=None, context_instance=None):
+    """
+    Loads the given template_name and renders it with the given dictionary as
+    context. The template_name may be a string to load a single template using
+    get_template, or it may be a tuple to use select_template to find one of
+    the templates in the list. Returns a string.
+    """
+    dictionary = dictionary or {}
+    if isinstance(template_name, (list, tuple)):
+        t = select_template(template_name)
+    else:
+        t = get_template(template_name)
+    if context_instance:
+        context_instance.update(dictionary)
+    else:
+        context_instance = Context(dictionary)
+    return t.render(context_instance)
+
+def select_template(template_name_list):
+    "Given a list of template names, returns the first that can be loaded."
+    for template_name in template_name_list:
+        try:
+            return get_template(template_name)
+        except TemplateDoesNotExist:
+            continue
+    # If we get here, none of the templates could be loaded
+    raise TemplateDoesNotExist(', '.join(template_name_list))
+
+add_to_builtins('django.template.loader_tags')