Yield type inferred incorrectly in nested Generators

[jolaf]

The following code:

from typing import Generator

from typeguard import TypeChecker

def a() -> Generator[str, None, None]:
    yield "OK"

def b() -> Generator[Generator[str, None, None], None, None]:
    yield a()
    yield a()

with TypeChecker('__main__'):
    for f in b():
        print(next(f))

produces the following output:

$ python3 Test.py 
OK
/usr/local/lib/python3.6/dist-packages/typeguard/__init__.py:932: TypeWarning: [MainThread] return from __main__.b() at Test.py:10: type of yielded value must be str; got generator instead
  warn(TypeWarning(memo, event, frame, exc))
OK

Note that the problem occurs only at the second yield, but not at the first one.

This is an old issue that I'm observing for some time, but I thought it to be a consequence of #77, but #77 is fixed now in v2.5.1, but this issue still persists.

[jolaf]

$ python3 --version
Python 3.6.8

[agronholm]

Using @typechecked instead gives another unexpected error: TypeError: type of value yielded from generator must be collections.abc.Generator; got typeguard.TypeCheckedGenerator instead
I guess I need to implicitly inherit from (or register with collections.abc.Generator) the TypeCheckedGenerator class?

[jolaf]

Note that the problem persists if a() is typed as Iterator[str] instead.

[agronholm]

Note that the problem persists if a() is typed as Iterator[str] instead.

Which seems strange because I didn't register TypeCheckedGenerator as an Iterator either. What am I missing here?

[agronholm]

Oh, sorry, I misread your post.

[agronholm]

What I meant to say is that this works:

from typing import Generator, Iterator

from typeguard import typechecked


@typechecked
def a() -> Iterator[str]:
    yield "OK"


@typechecked
def b() -> Generator[Iterator[str], None, None]:
    yield a()
    yield a()


for f in b():
    print(f.send(None))

[jolaf]

Crashes with import hook as well.

TypeGuardTest.py:

from typeguard.importhook import install_import_hook

install_import_hook('Test')

import Test

Test.py:

from typing import Generator

def a() -> Generator[str, None, None]:
    yield "OK"

def b() -> Generator[Generator[str, None, None], None, None]:
    yield a()
    yield a()

for f in b():
    print(next(f))

$ python3 TypeGuardTest.py 
Traceback (most recent call last):
  File "TypeGuardTest.py", line 5, in <module>
    import Test
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
  File "/usr/local/lib/python3.6/dist-packages/typeguard/importhook.py", line 80, in exec_module
    return super().exec_module(module)
  File "Test.py", line 10, in <module>
    for f in b():
  File "/usr/local/lib/python3.6/dist-packages/typeguard/__init__.py", line 635, in __next__
    return self.send(None)
  File "/usr/local/lib/python3.6/dist-packages/typeguard/__init__.py", line 652, in send
    check_type('value yielded from generator', value, self.__yield_type, memo=self.__memo)
  File "/usr/local/lib/python3.6/dist-packages/typeguard/__init__.py", line 516, in check_type
    check_type(argname, value, origin_type, memo)
  File "/usr/local/lib/python3.6/dist-packages/typeguard/__init__.py", line 544, in check_type
    format(argname, qualified_name(expected_type), qualified_name(value)))
TypeError: type of value yielded from generator must be collections.abc.Generator; got typeguard.TypeCheckedGenerator instead

Note that the crash seems different than the original one.
I'm not sure if it deserves a separate issue.

[jolaf]

This issue seems to be a real blocker for me, preventing me from running my full-scale software under typeguard with import hook. :(

[agronholm]

I've fixed this locally and I will soon push the changes once the tests and everything check out.

[agronholm]

This fixes generators for @typechecked. If it's still broken with the profiler hook, I frankly don't care.

[jolaf]

Okay, but it crashes with import hook too.
#81 (comment)

[agronholm]

Have you tested against the fix I made? The example code in the comment does work for me now.

[jolaf]

Yes, looks fixed, thanks!