Inference fails on assert-only function

[jtrakk]

I'm getting started with astroid. I want to find the functions that are called inside the test_sth function.

import astroid

source = """

def check_equal(a, b):
    assert a == b


def test_sth():
    check_equal(10, 11)

"""


def transform_call(node):
    for func in node.infer():
        print(func)


astroid.MANAGER.register_transform(astroid.nodes.Call, transform_call)
tree = astroid.parse(source)

I was expecting it to find the check_equal function. Running with python3.7, astroid 2.2.5, I get this exception:

Traceback

Traceback (most recent call last):
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/astroid/decorators.py", line 131, in raise_if_nothing_inferred
    yield next(generator)
StopIteration: {'node': <Call l.8 at 0x7fb9dcbfd5c0>, 'context': <astroid.context.InferenceContext object at 0x7fb9dcbfa0f8>}

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/user/tmp/inf.py", line 21, in <module>
    tree = astroid.parse(source)
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/astroid/builder.py", line 275, in parse
    return builder.string_build(code, modname=module_name, path=path)
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/astroid/builder.py", line 142, in string_build
    return self._post_build(module, "utf-8")
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/astroid/builder.py", line 160, in _post_build
    module = self._manager.visit_transforms(module)
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/astroid/manager.py", line 69, in visit_transforms
    return self._transform.visit(node)
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/astroid/transforms.py", line 89, in visit
    module.body = [self._visit(child) for child in module.body]
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/astroid/transforms.py", line 89, in <listcomp>
    module.body = [self._visit(child) for child in module.body]
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/astroid/transforms.py", line 54, in _visit
    visited = self._visit_generic(value)
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/astroid/transforms.py", line 61, in _visit_generic
    return [self._visit_generic(child) for child in node]
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/astroid/transforms.py", line 61, in <listcomp>
    return [self._visit_generic(child) for child in node]
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/astroid/transforms.py", line 67, in _visit_generic
    return self._visit(node)
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/astroid/transforms.py", line 54, in _visit
    visited = self._visit_generic(value)
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/astroid/transforms.py", line 67, in _visit_generic
    return self._visit(node)
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/astroid/transforms.py", line 57, in _visit
    return self._transform(node)
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/astroid/transforms.py", line 40, in _transform
    ret = transform_func(node)
  File "/home/user/tmp/inf.py", line 16, in transform_call
    for func in node.infer():
  File "/home/user/.local/pipx/venvs/ipython/lib/python3.7/site-packages/astroid/decorators.py", line 136, in raise_if_nothing_inferred
    raise exceptions.InferenceError(**error.args[0])
astroid.exceptions.InferenceError: Inference failed for <Call l.8 at 0x7fb9dcbfd5c0>.

I'm guessing this may be related to #485, but not sure. Am I doing something wrong or is there a workaround I can use? Thanks!

[PCManticore]

Thanks for the report! You are not doing anything wrong, it's just a bug in the inference engine. We should infer an empty return there, instead of crashing if there is no explicit return in the body of the function. A workaround for now is to modify your code to have a blank return in it or to modify your transform and look for any return statements in the body of the function before triggering the inference code for that function.