Merge pull request #66 from pytest-dev/teardown-exceptions

Capture exceptions during test teardown

Author: nicoddemus

docs/virtual_methods.rst

@@ -16,9 +16,11 @@ naturally in your python code::
             print('mouse released at: %s' % ev.pos())
 
 This works fine, but if python code in Qt virtual methods raise an exception
-``PyQt`` and ``PySide`` will just print the exception traceback to standard
+``PyQt4`` and ``PySide`` will just print the exception traceback to standard
 error, since this method is called deep within Qt's even loop handling and
-exceptions are not allowed at that point.
+exceptions are not allowed at that point. In ``PyQt5.5+``, exceptions in
+virtual methods will by default call ``abort()``, which will crash the
+interpreter.
 
 This might be surprising for python users which are used to exceptions
 being raised at the calling point: for example, the following code will just
@@ -61,4 +63,12 @@ Or even disable it for your entire project in your ``pytest.ini`` file:
     [pytest]
     qt_no_exception_capture = 1
 
-This might be desirable if you plan to install a custom exception hook.
+This might be desirable if you plan to install a custom exception hook.
+
+
+.. note::
+
+    Starting with ``PyQt5.5``, exceptions raised during virtual methods will
+    actually trigger an ``abort()``, crashing the Python interpreter. For this
+    reason, disabling exception capture in ``PyQt5.5+`` is not recommended
+    unless you install your own exception hook.

pytestqt/_tests/test_exceptions.py

@@ -1,6 +1,6 @@
 import pytest
 import sys
-from pytestqt.plugin import format_captured_exceptions
+from pytestqt.plugin import format_captured_exceptions, QT_API
 
 
 pytest_plugins = 'pytester'
@@ -75,8 +75,12 @@ def test_no_capture(testdir, no_capture_by_marker):
         ''')
     testdir.makepyfile('''
         import pytest
+        import sys
         from pytestqt.qt_compat import QWidget, QtCore
 
+        # PyQt 5.5+ will crash if there's no custom exception handler installed
+        sys.excepthook = lambda *args: None
+
         class MyWidget(QWidget):
 
             def mouseReleaseEvent(self, ev):
@@ -88,5 +92,36 @@ def test_widget(qtbot):
             qtbot.addWidget(w)
             qtbot.mouseClick(w, QtCore.Qt.LeftButton)
     '''.format(marker_code=marker_code))
-    res = testdir.inline_run()
-    res.assertoutcome(passed=1)
+    res = testdir.runpytest()
+    res.stdout.fnmatch_lines(['*1 passed*'])
+
+
+def test_exception_capture_on_teardown(testdir):
+    """
+    Exceptions should also be captured during test teardown.
+
+    :type testdir: TmpTestdir
+    """
+    testdir.makepyfile('''
+        import pytest
+        from pytestqt.qt_compat import QWidget, QtCore, QEvent
+
+        class MyWidget(QWidget):
+
+            def event(self, ev):
+                raise RuntimeError('event processed')
+
+        def test_widget(qtbot, qapp):
+            w = MyWidget()
+            # keep a reference to the widget so it will lives after the test
+            # ends. This will in turn trigger its event() during test tear down,
+            # raising the exception during its event processing
+            test_widget.w = w
+            qapp.postEvent(w, QEvent(QEvent.User))
+    ''')
+    res = testdir.runpytest('-s')
+    res.stdout.fnmatch_lines([
+        "*RuntimeError('event processed')*",
+        '*1 error*',
+    ])
+

pytestqt/plugin.py

@@ -544,8 +544,7 @@ def qtbot(qapp, request):
     that they are properly closed after the test ends.
     """
     result = QtBot()
-    no_capture = request.node.get_marker('qt_no_exception_capture') or \
-                 request.config.getini('qt_no_exception_capture')
+    no_capture = _exception_capture_disabled(request.node)
     if no_capture:
         yield result  # pragma: no cover
     else:
@@ -557,6 +556,13 @@ def qtbot(qapp, request):
     result._close()
 
 
+def _exception_capture_disabled(item):
+    """returns if exception capture is disabled for the given test item.
+    """
+    return item.get_marker('qt_no_exception_capture') or \
+           item.config.getini('qt_no_exception_capture')
+
+
 def pytest_addoption(parser):
     parser.addini('qt_no_exception_capture',
                   'disable automatic exception capture')
@@ -581,15 +587,21 @@ def pytest_addoption(parser):
 
 
 @pytest.mark.hookwrapper
-def pytest_runtest_teardown():
+def pytest_runtest_teardown(item):
     """
     Hook called after each test tear down, to process any pending events and
     avoiding leaking events to the next test.
     """
     yield
     app = QApplication.instance()
     if app is not None:
-        app.processEvents()
+        if _exception_capture_disabled(item):
+            app.processEvents()
+        else:
+            with capture_exceptions() as exceptions:
+                app.processEvents()
+            if exceptions:
+                pytest.fail('TEARDOWN ERROR: ' + format_captured_exceptions(exceptions))
 
 
 def pytest_configure(config):