airflow/templates.py

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import jinja2.sandbox


class SandboxedEnvironment(jinja2.sandbox.SandboxedEnvironment):
    """SandboxedEnvironment for Airflow task templates."""

    def is_safe_attribute(self, obj, attr, value):
        """
        Allow access to ``_`` prefix vars (but not ``__``).

        Unlike the stock SandboxedEnvironment, we allow access to "private" attributes (ones starting with
        ``_``) whilst still blocking internal or truely private attributes (``__`` prefixed ones).
        """
        return not jinja2.sandbox.is_internal_attribute(obj, attr)