Property Template::is_up_to_date breaks type hint contract

[Raiko Wielk]

environment.py::Template::is_up_to_date (https://github.com/pallets/jinja/blob/main/src/jinja2/environment.py#L1496) tries to call self._uptodate even if this correctly is a boolean and not callable, disallowing to correctly implement BaseLoader::get_source with an alway up_to_date get_source like here: https://github.com/peering-manager/peering-manager/blob/main/peering_manager/jinja2/loaders.py#L48

Overwrite a BaseLoaders get_source method returning a bool as last value as type hints allow and include template twice with cache enabled like here: https://github.com/peering-manager/peering-manager/blob/main/peering_manager/jinja2/loaders.py#L6

Untested example code snippet:

from jinja2 import BaseLoader


class MyLoader(BaseLoader):
    def get_source(self, environment, template):
        source = ...
        return source, template, True  # true should be allowed but jinja does not handle it here correctly according to type hints
...
---
...
{% include myTemp %}
{% include myTemp %}

Example trace

Traceback (most recent call last):
  File "/opt/peering-manager/peering_manager/jinja2/__init__.py", line 30, in render_jinja2
    return jinja2_template.render(**context)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/peering-manager/.venv/lib/python3.11/site-packages/jinja2/environment.py", line 1301, in render
    self.environment.handle_exception()
  File "/opt/peering-manager/.venv/lib/python3.11/site-packages/jinja2/environment.py", line 936, in handle_exception
    raise rewrite_traceback_stack(source=source)
  File "<template>", line 5, in top-level template code
  File "/opt/peering-manager/.venv/lib/python3.11/site-packages/jinja2/environment.py", line 1494, in is_up_to_date
    return self._uptodate()
           ^^^^^^^^^^^^^^^^
TypeError: 'bool' object is not callable
```

<!--
Describe the expected behavior that should have happened but didn't.
-->

Respect bools value and do not call it.

Environment:

- Python version: Python 3.11.5
- Jinja version: Jinja2==3.1.2

MR incoming...

[David Lord]

_uptodate has behaved the same way for 16 years, see the blame view on that line you identified: https://github.com/pallets/jinja/blame/main/src/jinja2/environment.py#L1496 It must be None or a callable, None indicates it's always up to date.

[Raiko Wielk]

Sorry, just misread the typehints, thanks for your quick response.

Just in case anyone stumbles into this via googe or so:

peering-manager/peering-manager#783

fixes this in this case at the right location which is not jinja here, my bad.