A Stab at Chameleon Integration in Morepath

gistfile1.py

import inspect
import morepath
import os


class ChameleonApp(morepath.App):

    @morepath.reify
    def chameleon_template_paths(self):
        """ Returns *absolute* paths to chameleon templates.

        The expected result is an iterable with one absolute path string per
        iteration, i.e. a list of directories. The directories are searched in
        order for the name of the template.

        Alternatively, a morepath app inheriting from ChameleonApp may be
        returned, which will result in the paths of that application being
        expanded.

        This is useful if one app with templates should be considered for
        the template lookup. For examle::

        @MyApp.setting(section='chameleon', name='search_paths')
        def get_search_paths():
            return ['templates']

        Will be expanded to::

        [
            'path to MyAppClass/templates'
        ]

        And::

        @MyDifferentApp.setting(section='chameleon', name='search_paths')
        def get_search_paths():
            return ['templates', MyApp]

        Will be expanded to:
        [
            'path to MyDifferentClass/templates',
            'path to MyAppClass/templates'
        ]

        """
        def expand_paths(paths):
            for ix, item in enumerate(paths):
                # if the returned item is
                if inspect.isclass(item):
                    for path in item().chameleon_template_paths:
                        yield path
                elif not item.startswith('/'):
                    yield os.path.join(
                        os.path.dirname(inspect.getfile(self.__class__)), item)
                else:
                    yield item

        return list(
            expand_paths(self.registry.settings.chameleon.search_paths))

    @morepath.reify
    def chameleon_templates(self):
        """ Returns an instanace of the chameleon.PageTemplateLoader with
        the template paths set to `chameleon_template_paths`

        """

        if self.registry.settings.chameleon.auto_reload:
            # this will result in a warning from chameleon at the moment:
            # https://github.com/malthe/chameleon/issues/183
            os.environ['CHAMELEON_RELOAD'] = 'true'

        # Only import after setting the environment variable, or it won't
        # be recognized.
        import chameleon
        return chameleon.PageTemplateLoader(self.chameleon_template_paths)


@ChameleonApp.setting(section="chameleon", name="search_paths")
def get_search_paths():
    """ Returns the chameleon search paths for the app. """
    raise NotImplementedError


@ChameleonApp.setting(section="chameleon", name="auto_reload")
def get_debug():
    """ Returns True if the template files should be automatically reloaded.

    """

    # TODO configure this for deployment
    return True


def render_chameleon(content, request):
    """ Renders the content with a chameleon template.
    The content is a dictionary of template variables used in the template.

    """
    template = request.app.chameleon_templates[content.pop('template')]
    rendered = template(**content)

    return morepath.request.Response(rendered, content_type='text/html')


@ChameleonApp.directive('chameleon')
class ChameleonDirective(morepath.directive.ViewDirective):
    """ Chameleon template view directive. Use like a morepath view::

    @MyApp.chameleon(model=Root, path='')
    def root(self, request, form=None):
        return {
            'template': 'blogpost.pt',
            'title': 'My Blog Post'
        }

    """
    def __init__(self, app, model, render=None, permission=None,
                 internal=False, **predicates):
        """ Register Chameleon view. """

        render = render or render_chameleon
        super(ChameleonDirective, self).__init__(
            app, model, render, permission, internal, **predicates)

    def group_key(self):
        return morepath.directive.ViewDirective