False positive E1111 assignment-from-no-return

[cdeil]

I'm getting false positives E1111 assignment-from-no-return from pylint for this project: https://github.com/gammapy/gammapy

Here's a minimal example to reproduce:

import numpy as np


class MyArray(np.ndarray):
    pass


a = np.ndarray((2,), buffer=np.array([1, 2, 3]), offset=np.int_().itemsize, dtype=int)
b = a.flatten()
print(b)

c = MyArray((2,), buffer=np.array([1, 2, 3]), offset=np.int_().itemsize, dtype=int)
d = c.flatten()
print(d)

The error reported is this:

$ pylint test.py -E
************* Module test
test.py:8:56: E1120: No value for argument 'value' in constructor call (no-value-for-parameter)
test.py:12:53: E1120: No value for argument 'value' in constructor call (no-value-for-parameter)
test.py:13:0: E1111: Assigning to function call which doesn't return (assignment-from-no-return)

The E1111 is a false positive, c.flatten() does return:

$ python test.py 
[2 3]
[2 3]

This is for current astroid and pylint master, which reports like this:

$ pylint --version
pylint 2.2.0
astroid 2.0.4
Python 3.6.0 | packaged by conda-forge | (default, Feb 10 2017, 07:08:35) 
[GCC 4.2.1 Compatible Apple LLVM 7.3.0 (clang-703.0.31)]

It's weird that the same false positive doesn't appear for the equivalent a.flatten() call.

Also, the message is cryptic:

Assigning to function call which doesn't return

I'm not assigning to a function call.
I'm making a function call c.flatten() and assign the return value to a local variable d.

[PCManticore]

Thanks for reporting the issue!

This is happening because the brain functions we have for numpy don't return anything, which confuses this check. Also agree on the fact that the message is cryptic, going to update it to something easier to understand.

[nils-wisiol]

This happens also with numpy's sign function, as can be seen in this minimal example:

from numpy import sign

x = sign(-1)
print(x)

pylint says test.py:3:0: E1111: Assigning result of a function call, where the function has no return (assignment-from-no-return)

pip freeze:

astroid==2.1.0
isort==4.3.4
lazy-object-proxy==1.3.1
mccabe==0.6.1
numpy==1.16.0
pkg-resources==0.0.0
pylint==2.2.2
six==1.12.0
typed-ast==1.2.0
wrapt==1.11.1

[PCManticore]

This is fixed in the master branch of astroid, just found out it's a duplicate of #2694 which was closed just today.