1 """

     2 Wrapper class that takes a list of template loaders as an argument and attempts

     3 to load templates from them in order, caching the result.

     4 """

     5 

     6 from django.template import TemplateDoesNotExist

     7 from django.template.loader import BaseLoader, get_template_from_string, find_template_loader, make_origin

     8 from django.utils.importlib import import_module

     9 from django.core.exceptions import ImproperlyConfigured

    10 

    11 class Loader(BaseLoader):

    12     is_usable = True

    13 

    14     def __init__(self, loaders):

    15         self.template_cache = {}

    16         self._loaders = loaders

    17         self._cached_loaders = []

    18 

    19     @property

    20     def loaders(self):

    21         # Resolve loaders on demand to avoid circular imports

    22         if not self._cached_loaders:

    23             for loader in self._loaders:

    24                 self._cached_loaders.append(find_template_loader(loader))

    25         return self._cached_loaders

    26 

    27     def find_template(self, name, dirs=None):

    28         for loader in self.loaders:

    29             try:

    30                 template, display_name = loader(name, dirs)

    31                 return (template, make_origin(display_name, loader, name, dirs))

    32             except TemplateDoesNotExist:

    33                 pass

    34         raise TemplateDoesNotExist(name)

    35 

    36     def load_template(self, template_name, template_dirs=None):

    37         if template_name not in self.template_cache:

    38             template, origin = self.find_template(template_name, template_dirs)

    39             if not hasattr(template, 'render'):

    40                 try:

    41                     template = get_template_from_string(template, origin, template_name)

    42                 except TemplateDoesNotExist:

    43                     # If compiling the template we found raises TemplateDoesNotExist, 

    44                     # back off to returning the source and display name for the template 

    45                     # we were asked to load. This allows for correct identification (later) 

    46                     # of the actual template that does not exist.

    47                     return template, origin

    48             self.template_cache[template_name] = template

    49         return self.template_cache[template_name], None

    50 

    51     def reset(self):

    52         "Empty the template cache."

    53         self.template_cache.clear()