Passing Jinja2 context to callable instance as first argument when the callable instance has __getattr__ method since Jinja2 2.11.0

[Jun Omae]

From comment:78:ticket:12130

The callable instance is Href instance.

See also

• ​https://github.com/pallets/jinja/blob/2.11.0/src/jinja2/runtime.py#L261
• ​https://github.com/pallets/jinja/blob/2.10.3/jinja2/runtime.py#L235

Jinja2 2.11.0

>>> import jinja2, sys
>>> jinja2.__version__
'2.11.0'
>>> from jinja2 import Template
>>> from trac.web.href import Href
>>> href = Href('/trac.cgi')
>>> Template('{{ href() }}').render(href=href)
"/trac.cgi/%3CContext%20%7B'range'%3A%20%3Cclass%20'range'%3E%2C%20'dict'%3A%20%3Cclass%20'dict'%3E%2C%20'lipsum'%3A%20%3Cfunction%20generate_lorem_ipsum%20at%200x7f0386031310%3E%2C%20'cycler'%3A%20%3Cclass%20'jinja2.utils.Cycler'%3E%2C%20'joiner'%3A%20%3Cclass%20'jinja2.utils.Joiner'%3E%2C%20'namespace'%3A%20%3Cclass%20'jinja2.utils.Namespace'%3E%2C%20'href'%3A%20%3CHref%20'/trac.cgi'%3E%7D%20of%20None%3E"
>>> class Foo(object):
...     def __getattr__(self, name):
...         sys.stderr.write('__getattr__({!r})\n'.format(name))
...         return self
...     def __call__(self, *args, **kwargs):
...         sys.stderr.write('__call__(args={!r}, kwargs={!r})\n'.format(args, kwargs))
...
>>> Template('{{ val() }}').render(val=Foo())
__getattr__('contextfunction')
__call__(args=(<Context {'range': <class 'range'>, 'dict': <class 'dict'>, 'lipsum': <function generate_lorem_ipsum at 0x7f0386031310>, 'cycler': <class 'jinja2.utils.Cycler'>, 'joiner': <class 'jinja2.utils.Joiner'>, 'namespace': <class 'jinja2.utils.Namespace'>, 'val': <__main__.Foo object at 0x7f038a15d160>} of None>,), kwargs={})
'None'

Jinja2 2.10.3

>>> import jinja2, sys
>>> jinja2.__version__
'2.10.3'
>>> from jinja2 import Template
>>> from trac.web.href import Href
>>> href = Href('/trac.cgi')
>>> Template('{{ href() }}').render(href=href)
'/trac.cgi'
>>> class Foo(object):
...     def __getattr__(self, name):
...         sys.stderr.write('__getattr__({!r})\n'.format(name))
...         return self
...     def __call__(self, *args, **kwargs):
...         sys.stderr.write('__call__(args={!r}, kwargs={!r})\n'.format(args, kwargs))
...
>>> Template('{{ val() }}').render(val=Foo())
__call__(args=(), kwargs={})
'None'

[Jun Omae]

Ad hoc patch:

trac/web/href.py

@@ -188 +188 @@
         return href
 
     def __getattr__(self, name):
+        if name in ('contextfunction', 'evalcontextfunction',
+                    'environmentfunction'):
+            raise AttributeError
         if name not in self._derived:
             self._derived[name] = lambda *args, **kw: self(name, *args, **kw)
         return self._derived[name]

[Ryan J Ollos]

Looks similar to ​Jinja2 issue #1139. Relevant change is ​70ea1d3e.

It wouldn't be an issue if Jinja2 tested the value: getattr(__obj, "contextfunction", 0) is True rather than just getattr(__obj, "contextfunction", 0).

[Jun Omae]

Proposed changes in [332bf1f51/jomae.git].

[Ryan J Ollos]

Looks good. Nice solution!

[Jun Omae]

Thanks for the review! Committed in [17238] and merged in [17239].