test: Correct MyPy typing for subtest decorator #23420

This is the part of the effort to make python typing correct #19389

The typing of the subtest decorator within p2p_segwit.py test file was incorrect.

Since subtest function is defined as a member of the class, it expects self as a first argument, and it is not provided. Hence the typing errors (that are currently suppressed by type: ignore).

(venv) vagrant@ubuntu-focal:/vagrant/test/functional$ mypy p2p_segwit.py 
p2p_segwit.py:298: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:327: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:358: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:447: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:519: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:561: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:659: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:670: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:737: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:826: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:866: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:941: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:977: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:1052: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:1089: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:1136: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:1220: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:1312: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:1406: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:1440: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:1543: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:1729: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:1782: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:1881: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:1983: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
p2p_segwit.py:2027: error: Argument 1 to "subtest" has incompatible type "Callable[[SegWitTest], Any]"; expected "SegWitTest"
Found 26 errors in 1 file (checked 1 source file)

However, the tests are passing, because there is no self argument passed when it is called as a decorator.

There is also suppressed pylint error # noqa: N805 pointing to the same issue.

N805 first argument of a method should be named 'self'

So the solution is to move the subtest definition outside the class, so the self argument is no longer required.

After doing so, both mypy and unittests are successfully passing:

(venv) vagrant@ubuntu-focal:/vagrant/test/functional$ mypy p2p_segwit.py 
Success: no issues found in 1 source file

(venv) vagrant@ubuntu-focal:/vagrant/test/functional$ ./test_runner.py p2p_segwit
Temporary test directory at /tmp/test_runner_₿_🏃_20211103_011449
Running Unit Tests for Test Framework Modules
..........
----------------------------------------------------------------------
Ran 10 tests in 0.546s

OK
Remaining jobs: [p2p_segwit.py]
1/1 - p2p_segwit.py passed, Duration: 81 s                                                                                                                      

TEST          | STATUS    | DURATION

p2p_segwit.py | ✓ Passed  | 81 s

ALL           | ✓ Passed  | 81 s (accumulated) 
Runtime: 81 s

@MarcoFalke Do you still think this should be merged, despite the parent issue has been closed?

@prius yes this should be left open.

Code review ACK 83b32fe599c91fc52d89f4172c0b064d643620d8

I would prefer for the @ to be removed from the commit message and PR title, because otherwise it it will notify the github user subtest every time something is done with the commit.

@laanwj Good catch! Removed @ from everywhere.

Removed @ from everywhere.

It's still in the commit message.

@fanquake Commit message changed to be the same as PR title.

ACK 467fe5779ca85bd8d58fde65948ffc8c35078e60