Refactor Qt brain transforms to handle PyQt and PySide

[emmanuel-ferdman]

Type of Changes

	Type
✓	🐛 Bug fix

Description

This PR rewrites astroid/brain/brain_qt.py to correctly infer Qt signals for both PyQt and PySide, regardless of how the binding exposes them: Function-style signals (descriptor) or Class-style signals. Main changes:

• Reorganized astroid/brain/brain_qt.py to share explicit PyQt/PySide signal templates, restoring connect/disconnect/emit inference for both toolkits. I believe it also improves readability of code.
• Handle function-style vs class-style signals: Some bindings (e.g., PySide ≥ 5.15.2 / PySide6) expose Signal via the descriptor protocol, so it infers as a FunctionDef. The transform now catches that path and attaches the expected members. See Example 1 (subclassed QTimer.timeout) and Example 2 (class-style Signal() instance) below. Other bindings (e.g., PyQt5/6) expose pyqtSignal as a class, so it infers as a ClassDef. We register a matching class transform there as well.
• Enabled the PyQt6 brain tests across every supported Python version (Previously it was only for 3.10).

Please note that I tried to add tests to PySide6 but it looks like PyQt6 and PySide6 cannot coexist in a single Linux process because their wheels bundle different Qt 6 library revisions (similiary to concolution in work made in PR #1654). Due to this limiation, I added pragma: no cover for the PySide code branches.

Previously failing examples - Example 1:

from PySide6.QtCore import QTimer


class CustomTimer(QTimer):
    def __init__(self) -> None:
        super().__init__()
        self.timeout.connect(self.on_timeout)

    def on_timeout(self) -> None:
        pass


def build_timer() -> CustomTimer:
    timer = CustomTimer()
    timer.timeout.disconnect()
    return timer

Used to emit:

input.py:8:8: E1101: Method '<no-name>' has no 'connect' member (no-member)
input.py:16:4: E1101: Method '<no-name>' has no 'disconnect' member (no-member)

Example 2:

from PySide6.QtCore import Signal


sig = Signal()
sig.connect(lambda: None)

Used to emit:

input.py:5:0: E1101: Instance of 'Signal' has no 'connect' member (no-member)

The same pattern affected PyQt5 and PyQt6 as well (with their appropriate API/syntax).

Fixes #2850.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.40%. Comparing base (ab119c2) to head (dc6d093).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2863      +/-   ##
==========================================
+ Coverage   93.35%   93.40%   +0.05%     
==========================================
  Files          92       92              
  Lines       11190    11209      +19     
==========================================
+ Hits        10446    10470      +24     
+ Misses        744      739       -5     

Flag	Coverage Δ
linux	93.27% <100.00%> (+0.05%)	⬆️
pypy	93.40% <100.00%> (+0.05%)	⬆️
windows	93.38% <100.00%> (+0.05%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
astroid/brain/brain_qt.py	100.00% <100.00%> (+17.24%)	⬆️

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[Pierre-Sassoulas]

The test matrix for both pyqt 5 and 6 would better work in a separated repository, but we only have an idea of creating astroid plugin repository at this point. Question for other maintainers : This might be the occasion to do a proof of concept for astroid plugin ?

[Pierre-Sassoulas]

👍

[Pierre-Sassoulas]

Should we add a matrix for pyqt 5 / 6 ?