#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:
> 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(
> }}}
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 }}
}}}
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#comment:1>
Django <https://code.djangoproject.com/>
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