[Django] #33653: no signature found for builtin raised for non-existant items

[Django]

#33653: no signature found for builtin raised for non-existant items
-------------------------------------------+--------------------------
Reporter: Daniel | Owner: nobody
Type: Bug | Status: new
Component: Template system | Version: 3.2
Severity: Normal | Keywords: template
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------------+--------------------------
Found during a 2.2 -> 3.2 upgrade:

**Given a template**:

{{{
{{ foo }}
}}}

where `foo` is non-existant, it returns nothing, empty. (That's good)

{{{
{{ foo.count }}
}}}

also empty (Also good)

{{{
{% include 'second_template.html' with bar=foo %}
}}}

and then in `second_template.html` having:

{{{
{{ foo.count }}
}}}

results in
{{{
File "/Users/daniel/src/django-bug-test/.v/lib/python3.8/site-
packages/django/template/base.py", line 861, in _resolve_lookup
signature = inspect.signature(current)
File "/Users/daniel/.pyenv/versions/3.8.3/lib/python3.8/inspect.py",
line 3093, in signature
return Signature.from_callable(obj, follow_wrapped=follow_wrapped)
File "/Users/daniel/.pyenv/versions/3.8.3/lib/python3.8/inspect.py",
line 2842, in from_callable
return _signature_from_callable(obj, sigcls=cls,
File "/Users/daniel/.pyenv/versions/3.8.3/lib/python3.8/inspect.py",
line 2296, in _signature_from_callable
return _signature_from_builtin(sigcls, obj,
File "/Users/daniel/.pyenv/versions/3.8.3/lib/python3.8/inspect.py",
line 2107, in _signature_from_builtin
raise ValueError("no signature found for builtin {!r}".format(func))

Exception Type: ValueError at /
Exception Value: no signature found for builtin <built-in method count of
str object at 0x1100ff2f0>
}}}

On django 2.2, this would not crash, but resulted in empty (as I
expected).

this seems to fix it for me:
{{{
diff --git a/django/template/base.py b/django/template/base.py
index a1ab437eca..f95aec5a90 100644
--- a/django/template/base.py
+++ b/django/template/base.py
@@ -913,15 +913,19 @@ def _resolve_lookup(self, context):
try: # method call (assuming no args required)
current = current()
except TypeError:
- signature = inspect.signature(current)
try:
- signature.bind()
- except TypeError: # arguments *were*
required
- current = (
-
context.template.engine.string_if_invalid
- ) # invalid method call
+ signature = inspect.signature(current)
+ except ValueError: # python builtins might
not have signature
+ current =
context.template.engine.string_if_invalid
else:
- raise
+ try:
+ signature.bind()
+ except TypeError: # arguments *were*
required
+ current = (
+
context.template.engine.string_if_invalid
+ ) # invalid method call
+ else:
+ raise
except Exception as e:
template_name = getattr(context, "template_name", None) or
"unknown"
logger.debug(
}}}

--
Ticket URL: <https://code.djangoproject.com/ticket/33653>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.

[Django]

#33653: no signature found for builtin raised for non-existant items

---------------------------------+--------------------------------------

Reporter: Daniel | Owner: nobody
Type: Bug | Status: new
Component: Template system | Version: 3.2

Severity: Normal | Resolution:

Keywords: template | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0

---------------------------------+--------------------------------------
Description changed by Daniel:

Old description:

New description:

Found during a 2.2 -> 3.2 upgrade:

**Given a template**:

{{{
{{ foo }}
}}}

where `foo` is non-existant, it returns nothing, empty. (That's good)

{{{
{{ foo.count }}
}}}

also empty (Also good)

{{{
{% include 'second_template.html' with bar=foo %}
}}}

and then in `second_template.html` having:

{{{
{{ bar.count }}
}}}

--

--
Ticket URL: <https://code.djangoproject.com/ticket/33653#comment:1>

[Django]

#33653: no signature found for builtin raised for non-existant items
---------------------------------+--------------------------------------
Reporter: Daniel | Owner: nobody
Type: Bug | Status: new
Component: Template system | Version: 3.2
Severity: Normal | Resolution:
Keywords: template | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
---------------------------------+--------------------------------------

Comment (by jerch):

Isn't a bug, that the template resolver tries to step into
`''.<some_builtin_method>` here? Maybe the `for bit in self.lookups:`
descent could exit as soon as `current` drops to an empty string?

--
Ticket URL: <https://code.djangoproject.com/ticket/33653#comment:2>