feat: add error exceptions_as_dialog context manager to catch and show Exceptions (#191)

* feat: add error messagebox context

* typing

* Update src/superqt/utils/_errormsg_context.py

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

* add tests

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

* docs: add docs

* test button result

* format doc

* docs: update docs

* docs

* add dialog example

* pass flags

* skip mac ci pyside6

---------

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

@@ -1,8 +1,13 @@
+import os
+import sys
 from unittest.mock import Mock
 
-from qtpy.QtCore import QObject, Signal
+import pytest
+import qtpy
+from qtpy.QtCore import QObject, QTimer, Signal
+from qtpy.QtWidgets import QApplication, QErrorMessage, QMessageBox
 
-from superqt.utils import signals_blocked
+from superqt.utils import exceptions_as_dialog, signals_blocked
 from superqt.utils._util import get_max_args
 
 
@@ -91,3 +96,46 @@ def test_get_max_args_methods():
     assert get_max_args(A().fun1) == 0
     assert get_max_args(A().fun2) == 1
     assert get_max_args(A()) == 2
+
+
+MAC_CI_PYSIDE6 = bool(
+    sys.platform == "darwin" and os.getenv("CI") and qtpy.API_NAME == "PySide6"
+)
+
+
+@pytest.mark.skipif(MAC_CI_PYSIDE6, reason="still hangs on mac ci with pyside6")
+def test_exception_context(qtbot, qapp: QApplication) -> None:
+    def accept():
+        for wdg in qapp.topLevelWidgets():
+            if isinstance(wdg, QMessageBox):
+                wdg.button(QMessageBox.StandardButton.Ok).click()
+
+    with exceptions_as_dialog():
+        QTimer.singleShot(0, accept)
+        raise Exception("This will be caught and shown in a QMessageBox")
+
+    with pytest.raises(ZeroDivisionError), exceptions_as_dialog(ValueError):
+        1 / 0  # noqa
+
+    with exceptions_as_dialog(msg_template="Error: {exc_value}"):
+        QTimer.singleShot(0, accept)
+        raise Exception("This message will be used as 'exc_value'")
+
+    err = QErrorMessage()
+    with exceptions_as_dialog(use_error_message=err):
+        QTimer.singleShot(0, err.accept)
+        raise AssertionError("Uncheck the checkbox to ignore this in the future")
+
+    # tb formatting smoke test, and return value checking
+    exc = ValueError("Bad Val")
+    with exceptions_as_dialog(
+        msg_template="{tb}",
+        buttons=QMessageBox.StandardButton.Ok | QMessageBox.StandardButton.Cancel,
+    ) as ctx:
+        qtbot.addWidget(ctx.dialog)
+        QTimer.singleShot(100, accept)
+        raise exc
+
+    assert isinstance(ctx.dialog, QMessageBox)
+    assert ctx.dialog.result() == QMessageBox.StandardButton.Ok
+    assert ctx.exception is exc