fix: fix parameter inspection on ensure_thread decorators (alternate) (#185)

* fix: use different approach

* test: apply fixes

* back to signature

* fix get_max_args

* IMPORT THE FUTURE

* try or return None

* check for callable

* Update test_utils.py

Co-authored-by: Grzegorz Bokota <bokota+github@gmail.com>

* style: [pre-commit.ci] auto fixes [...]

---------

Co-authored-by: Grzegorz Bokota <bokota+github@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

tests/test_utils.py

@@ -3,6 +3,7 @@ from unittest.mock import Mock
 from qtpy.QtCore import QObject, Signal
 
 from superqt.utils import signals_blocked
+from superqt.utils._util import get_max_args
 
 
 def test_signal_blocker(qtbot):
@@ -27,3 +28,66 @@ def test_signal_blocker(qtbot):
         qtbot.wait(10)
 
     receiver.assert_not_called()
+
+
+def test_get_max_args_simple():
+    def fun1():
+        pass
+
+    assert get_max_args(fun1) == 0
+
+    def fun2(a):
+        pass
+
+    assert get_max_args(fun2) == 1
+
+    def fun3(a, b=1):
+        pass
+
+    assert get_max_args(fun3) == 2
+
+    def fun4(a, *, b=2):
+        pass
+
+    assert get_max_args(fun4) == 1
+
+    def fun5(a, *b):
+        pass
+
+    assert get_max_args(fun5) is None
+
+    assert get_max_args(print) is None
+
+
+def test_get_max_args_wrapped():
+    from functools import partial, wraps
+
+    def fun1(a, b):
+        pass
+
+    assert get_max_args(partial(fun1, 1)) == 1
+
+    def dec(fun):
+        @wraps(fun)
+        def wrapper(*args, **kwargs):
+            return fun(*args, **kwargs)
+
+        return wrapper
+
+    assert get_max_args(dec(fun1)) == 2
+
+
+def test_get_max_args_methods():
+    class A:
+        def fun1(self):
+            pass
+
+        def fun2(self, a):
+            pass
+
+        def __call__(self, a, b=1):
+            pass
+
+    assert get_max_args(A().fun1) == 0
+    assert get_max_args(A().fun2) == 1
+    assert get_max_args(A()) == 2