Class Extension

tools/inspector_protocol/jinja2/ext.py:43–129

Extensions can be used to add extra functionality to the Jinja template system at the parser level. Custom extensions are bound to an environment but may not store environment specific data on `self`. The reason for this is that an extension can be bound to another environment (for

class Extension(with_metaclass(ExtensionRegistry, object)):
    """Extensions can be used to add extra functionality to the Jinja template
    system at the parser level.  Custom extensions are bound to an environment
    but may not store environment specific data on `self`.  The reason for
    this is that an extension can be bound to another environment (for
    overlays) by creating a copy and reassigning the `environment` attribute.

    As extensions are created by the environment they cannot accept any
    arguments for configuration.  One may want to work around that by using
    a factory function, but that is not possible as extensions are identified
    by their import name.  The correct way to configure the extension is
    storing the configuration values on the environment.  Because this way the
    environment ends up acting as central configuration storage the
    attributes may clash which is why extensions have to ensure that the names
    they choose for configuration are not too generic.  ``prefix`` for example
    is a terrible name, ``fragment_cache_prefix`` on the other hand is a good
    name as includes the name of the extension (fragment cache).
    """

    #: if this extension parses this is the list of tags it's listening to.
    tags = set()

    #: the priority of that extension.  This is especially useful for
    #: extensions that preprocess values.  A lower value means higher
    #: priority.
    #:
    #: .. versionadded:: 2.4
    priority = 100

    def __init__(self, environment):
        self.environment = environment

    def bind(self, environment):
        """Create a copy of this extension bound to another environment."""
        rv = object.__new__(self.__class__)
        rv.__dict__.update(self.__dict__)
        rv.environment = environment
        return rv

    def preprocess(self, source, name, filename=None):
        """This method is called before the actual lexing and can be used to
        preprocess the source.  The `filename` is optional.  The return value
        must be the preprocessed source.
        """
        return source

    def filter_stream(self, stream):
        """It's passed a :class:`~jinja2.lexer.TokenStream` that can be used
        to filter tokens returned.  This method has to return an iterable of
        :class:`~jinja2.lexer.Token`\\s, but it doesn't have to return a
        :class:`~jinja2.lexer.TokenStream`.

        In the `ext` folder of the Jinja2 source distribution there is a file
        called `inlinegettext.py` which implements a filter that utilizes this
        method.
        """
        return stream