Class Context

tools/inspector_protocol/jinja2/runtime.py:133–313

The template context holds the variables of a template. It stores the values passed to the template and also the names the template exports. Creating instances is neither supported nor useful as it's created automatically at various stages of the template evaluation and should not b

class Context(with_metaclass(ContextMeta)):
    """The template context holds the variables of a template.  It stores the
    values passed to the template and also the names the template exports.
    Creating instances is neither supported nor useful as it's created
    automatically at various stages of the template evaluation and should not
    be created by hand.

    The context is immutable.  Modifications on :attr:`parent` **must not**
    happen and modifications on :attr:`vars` are allowed from generated
    template code only.  Template filters and global functions marked as
    :func:`contextfunction`\\s get the active context passed as first argument
    and are allowed to access the context read-only.

    The template context supports read only dict operations (`get`,
    `keys`, `values`, `items`, `iterkeys`, `itervalues`, `iteritems`,
    `__getitem__`, `__contains__`).  Additionally there is a :meth:`resolve`
    method that doesn't fail with a `KeyError` but returns an
    :class:`Undefined` object for missing variables.
    """
    # XXX: we want to eventually make this be a deprecation warning and
    # remove it.
    _legacy_resolve_mode = False
    _fast_resolve_mode = False

    def __init__(self, environment, parent, name, blocks):
        self.parent = parent
        self.vars = {}
        self.environment = environment
        self.eval_ctx = EvalContext(self.environment, name)
        self.exported_vars = set()
        self.name = name

        # create the initial mapping of blocks.  Whenever template inheritance
        # takes place the runtime will update this mapping with the new blocks
        # from the template.
        self.blocks = dict((k, [v]) for k, v in iteritems(blocks))

        # In case we detect the fast resolve mode we can set up an alias
        # here that bypasses the legacy code logic.
        if self._fast_resolve_mode:
            self.resolve_or_missing = MethodType(resolve_or_missing, self)

    def super(self, name, current):
        """Render a parent block."""
        try:
            blocks = self.blocks[name]
            index = blocks.index(current) + 1
            blocks[index]
        except LookupError:
            return self.environment.undefined('there is no parent block '
                                              'called %r.' % name,
                                              name='super')
        return BlockReference(name, self, blocks, index)

    def get(self, key, default=None):
        """Returns an item from the template context, if it doesn't exist
        `default` is returned.
        """