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Fix is_simple_callable with variable args, kwargs #4622

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Merged
merged 2 commits into from
Oct 25, 2016
Merged

Fix is_simple_callable with variable args, kwargs #4622

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91d6fb1
Add regression test for #4602
Oct 24, 2016
8952096
Check args and kwargs in is_simple_callable
Oct 24, 2016
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9 changes: 7 additions & 2 deletions rest_framework/fields.py
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Original file line number Diff line number Diff line change
Expand Up @@ -54,12 +54,17 @@ def is_simple_callable(obj):
"""
True if the object is a callable that takes no arguments.
"""
if not callable(obj):
if not (inspect.isfunction(obj) or inspect.ismethod(obj)):
return False

sig = inspect.signature(obj)
params = sig.parameters.values()
return all(param.default != param.empty for param in params)
return all(
param.kind == param.VAR_POSITIONAL or
param.kind == param.VAR_KEYWORD or
param.default != param.empty
for param in params
)
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@rpkilby: Can you just explain this call to me, just for my sanity? 🙂

I'm expecting any(iterable) — it looks like bool or bool or generator, so why isn't it this:

>>> a = True
>>> b = True
>>> def c():
...     yield True
...     yield False
>>> all(a or b or c())
TypeError: 'bool' object is not iterable

Sorry for being slow. Thanks!

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@carltongibson carltongibson Oct 26, 2016 •
edited
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OK. 1 second after Comment it becomes clear. ... — even seeing it though, I still struggle to read it right...

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@carltongibson - it probably wouldn't have hurt to have added a second set of parens wrapping the conditions

return all((
        param.kind == param.VAR_POSITIONAL or
        param.kind == param.VAR_KEYWORD or
        param.default != param.empty
    ) for param in params
)

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Yeah, that's kind to of where I came to. (That vs a nested any)

It's fine.


else:
def is_simple_callable(obj):
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23 changes: 23 additions & 0 deletions tests/test_fields.py
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Expand Up @@ -37,6 +37,9 @@ def valid(self):
def valid_kwargs(self, param='value'):
pass

def valid_vargs_kwargs(self, *args, **kwargs):
pass

def invalid(self, param):
pass

Expand All @@ -45,11 +48,13 @@ def invalid(self, param):
# unbound methods
assert not is_simple_callable(Foo.valid)
assert not is_simple_callable(Foo.valid_kwargs)
assert not is_simple_callable(Foo.valid_vargs_kwargs)
assert not is_simple_callable(Foo.invalid)

# bound methods
assert is_simple_callable(Foo().valid)
assert is_simple_callable(Foo().valid_kwargs)
assert is_simple_callable(Foo().valid_vargs_kwargs)
assert not is_simple_callable(Foo().invalid)

def test_function(self):
Expand All @@ -59,13 +64,31 @@ def simple():
def valid(param='value', param2='value'):
pass

def valid_vargs_kwargs(*args, **kwargs):
pass

def invalid(param, param2='value'):
pass

assert is_simple_callable(simple)
assert is_simple_callable(valid)
assert is_simple_callable(valid_vargs_kwargs)
assert not is_simple_callable(invalid)

def test_4602_regression(self):
from django.db import models

class ChoiceModel(models.Model):
choice_field = models.CharField(
max_length=1, default='a',
choices=(('a', 'A'), ('b', 'B')),
)

class Meta:
app_label = 'tests'

assert is_simple_callable(ChoiceModel().get_choice_field_display)

@unittest.skipUnless(typings, 'requires python 3.5')
def test_type_annotation(self):
# The annotation will otherwise raise a syntax error in python < 3.5
Expand Down
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