Ensure that widgets can be garbage collected on each platform

changes/2088.misc.rst

@@ -0,0 +1 @@
+Test garbage collection of widgets on all platforms.

testbed/tests/conftest.py

@@ -19,18 +19,18 @@
 
 # Use this for widgets or tests which are not supported on some platforms, but could be
 # supported in the future.
-def skip_on_platforms(*platforms):
+def skip_on_platforms(*platforms, reason=None):
     current_platform = toga.platform.current_platform
     if current_platform in platforms:
-        skip(f"not yet implemented on {current_platform}")
+        skip(reason or f"not yet implemented on {current_platform}")
 
 
 # Use this for widgets or tests which are not supported on some platforms, and will not
 # be supported in the foreseeable future.
-def xfail_on_platforms(*platforms):
+def xfail_on_platforms(*platforms, reason=None):
     current_platform = toga.platform.current_platform
     if current_platform in platforms:
-        skip(f"not applicable on {current_platform}")
+        skip(reason or f"not applicable on {current_platform}")
 
 
 @fixture(autouse=True)

testbed/tests/widgets/conftest.py

@@ -1,10 +1,13 @@
+import gc
+import weakref
 from unittest.mock import Mock
 
 from pytest import fixture
 
 import toga
 from toga.style.pack import TOP
 
+from ..conftest import skip_on_platforms, xfail_on_platforms
 from .probe import get_probe
 
 
@@ -78,3 +81,31 @@ def verify_focus_handlers():
 def verify_vertical_alignment():
     """The widget's default vertical alignment"""
     return TOP
+
+
+def build_cleanup_test(
+    widget_constructor, args=None, kwargs=None, skip_platforms=(), xfail_platforms=()
+):
+    async def test_cleanup():
+        nonlocal args, kwargs
+
+        skip_on_platforms(*skip_platforms)
+        xfail_on_platforms(*xfail_platforms, reason="Leaks memory")
+
+        if args is None:
+            args = ()
+
+        if kwargs is None:
+            kwargs = {}
+
+        widget = widget_constructor(*args, **kwargs)
+        ref = weakref.ref(widget)
+
+        # Args or kwargs may hold a backref to the widget itself, for example if they
+        # are widget content. Ensure that they are deleted before garbage collection.
+        del widget, args, kwargs
+        gc.collect()
+
+        assert ref() is None
+
+    return test_cleanup

testbed/tests/widgets/test_activityindicator.py

@@ -3,6 +3,7 @@
 import toga
 
 from ..conftest import skip_on_platforms
+from .conftest import build_cleanup_test
 from .properties import (  # noqa: F401
     test_enable_noop,
     test_focus_noop,
@@ -15,6 +16,11 @@ async def widget():
     return toga.ActivityIndicator()
 
 
+test_cleanup = build_cleanup_test(
+    toga.ActivityIndicator, skip_platforms=("android", "windows")
+)
+
+
 async def test_start_stop(widget, probe):
     "The activity indicator can be started and stopped"
     # Widget should be initially stopped

testbed/tests/widgets/test_box.py

@@ -3,6 +3,7 @@
 import toga
 from toga.style import Pack
 
+from .conftest import build_cleanup_test
 from .properties import (  # noqa: F401
     test_background_color,
     test_background_color_reset,
@@ -15,3 +16,6 @@
 @pytest.fixture
 async def widget():
     return toga.Box(style=Pack(width=100, height=200))
+
+
+test_cleanup = build_cleanup_test(toga.Box, xfail_platforms=("iOS",))

testbed/tests/widgets/test_button.py

@@ -7,6 +7,7 @@
 
 from ..assertions import assert_color
 from ..data import TEXTS
+from .conftest import build_cleanup_test
 from .properties import (  # noqa: F401
     test_background_color,
     test_background_color_reset,
@@ -31,6 +32,11 @@ async def widget():
     return toga.Button("Hello")
 
 
+test_cleanup = build_cleanup_test(
+    toga.Button, args=("Hello",), skip_platforms=("android",)
+)
+
+
 async def test_text(widget, probe):
     "The text displayed on a button can be changed"
     initial_height = probe.height

testbed/tests/widgets/test_canvas.py

@@ -21,6 +21,7 @@
 from toga.fonts import BOLD
 from toga.style.pack import SYSTEM, Pack
 
+from .conftest import build_cleanup_test
 from .properties import (  # noqa: F401
     test_background_color,
     test_background_color_reset,
@@ -108,6 +109,9 @@ def assert_pixel(image, x, y, color):
     assert image.getpixel((x, y)) == color
 
 
+test_cleanup = build_cleanup_test(toga.Canvas, xfail_platforms=("android",))
+
+
 async def test_resize(widget, probe, on_resize_handler):
     "Resizing the widget causes on-resize events"
     # Make the canvas visible against window background.

testbed/tests/widgets/test_dateinput.py

@@ -6,6 +6,7 @@
 import toga
 
 from ..conftest import skip_on_platforms
+from .conftest import build_cleanup_test
 from .properties import (  # noqa: F401
     test_background_color,
     test_background_color_reset,
@@ -82,6 +83,13 @@ async def widget():
     return toga.DateInput()
 
 
+test_cleanup = build_cleanup_test(
+    toga.DateInput,
+    skip_platforms=("macOS", "iOS", "linux"),
+    xfail_platforms=("android",),
+)
+
+
 async def test_init():
     "Properties can be set in the constructor"
     skip_on_platforms("macOS", "iOS", "linux")

testbed/tests/widgets/test_detailedlist.py

@@ -6,6 +6,7 @@
 from toga.sources import ListSource
 from toga.style.pack import Pack
 
+from .conftest import build_cleanup_test
 from .properties import (  # noqa: F401
     test_enable_noop,
     test_flex_widget_size,
@@ -74,6 +75,11 @@ async def widget(
     )
 
 
+test_cleanup = build_cleanup_test(
+    toga.DetailedList, xfail_platforms=("android", "linux")
+)
+
+
 async def test_scroll(widget, probe):
     """The detailedList can be scrolled"""
 

testbed/tests/widgets/test_divider.py

@@ -4,6 +4,7 @@
 from toga.constants import Direction
 from toga.style.pack import COLUMN, ROW
 
+from .conftest import build_cleanup_test
 from .properties import (  # noqa: F401
     test_enable_noop,
     test_focus_noop,
@@ -15,6 +16,9 @@ async def widget():
     return toga.Divider()
 
 
+test_cleanup = build_cleanup_test(toga.Divider, xfail_platforms=("iOS",))
+
+
 async def test_directions(widget, probe):
     "The divider has the right size as direction is changed"
     # Widget should be initially horizontal.

testbed/tests/widgets/test_imageview.py

@@ -3,6 +3,7 @@
 import toga
 from toga.style.pack import COLUMN, ROW
 
+from .conftest import build_cleanup_test
 from .properties import (  # noqa: F401
     test_background_color,
     test_background_color_reset,
@@ -17,6 +18,11 @@ async def widget():
     return toga.ImageView(image="resources/sample.png")
 
 
+test_cleanup = build_cleanup_test(
+    toga.ImageView, kwargs={"image": "resources/sample.png"}, xfail_platforms=("iOS",)
+)
+
+
 async def test_implicit_size(widget, probe, container_probe):
     """If the image view size is implicit, the image provides flexible size hints."""
 

testbed/tests/widgets/test_label.py

@@ -2,6 +2,7 @@
 
 import toga
 
+from .conftest import build_cleanup_test
 from .properties import (  # noqa: F401
     test_alignment,
     test_background_color,
@@ -24,6 +25,9 @@ async def widget():
     return toga.Label("hello, this is a label")
 
 
+test_cleanup = build_cleanup_test(toga.Label, args=("hello, this is a label",))
+
+
 async def test_multiline(widget, probe):
     """If the label contains multiline text, it resizes vertically."""
 

testbed/tests/widgets/test_mapview.py

@@ -8,6 +8,7 @@
 import toga
 from toga.style import Pack
 
+from .conftest import build_cleanup_test
 from .properties import (  # noqa: F401
     test_flex_widget_size,
 )
@@ -57,6 +58,9 @@ async def widget(on_select):
         toga.App.app._gc_protector.append(widget)
 
 
+test_cleanup = build_cleanup_test(toga.MapView, xfail_platforms=("android",))
+
+
 # The next two tests fail about 75% of the time in the macOS x86_64 CI configuration.
 # The failure mode appears to be that the widget *exists*, but doesn't respond to
 # changes in location or zoom. I've been unable to reproduce this in actual testing on

testbed/tests/widgets/test_multilinetextinput.py

@@ -3,6 +3,7 @@
 import toga
 from toga.style import Pack
 
+from .conftest import build_cleanup_test
 from .properties import (  # noqa: F401
     test_alignment,
     test_background_color,
@@ -42,6 +43,11 @@ def verify_font_sizes():
     return False, False
 
 
+test_cleanup = build_cleanup_test(
+    toga.MultilineTextInput, xfail_platforms=("android", "linux")
+)
+
+
 async def test_scroll_position(widget, probe):
     "The widget can be programmatically scrolled."
     # The document initially fits within the visible area.

testbed/tests/widgets/test_numberinput.py

@@ -6,6 +6,7 @@
 import toga
 
 from ..conftest import skip_on_platforms
+from .conftest import build_cleanup_test
 from .properties import (  # noqa: F401
     test_alignment,
     test_background_color,
@@ -41,6 +42,9 @@ def verify_focus_handlers():
     return False
 
 
+test_cleanup = build_cleanup_test(toga.NumberInput, xfail_platforms=("android",))
+
+
 async def test_on_change_handler(widget, probe):
     "The on_change handler is triggered when the user types."
     widget.step = "0.01"

testbed/tests/widgets/test_optioncontainer.py

@@ -6,6 +6,7 @@
 from toga.colors import CORNFLOWERBLUE, GOLDENROD, REBECCAPURPLE, SEAGREEN
 from toga.style.pack import Pack
 
+from .conftest import build_cleanup_test
 from .probe import get_probe
 from .properties import (  # noqa: F401
     test_enable_noop,
@@ -71,6 +72,14 @@ async def widget(content1, content2, content3, on_select_handler):
     )
 
 
+test_cleanup = build_cleanup_test(
+    # Pass a function here to prevent init of toga.Box() in a different thread than
+    # toga.OptionContainer. This would raise a runtime error on Windows.
+    lambda: toga.OptionContainer(content=[("Tab 1", toga.Box())]),
+    xfail_platforms=("android", "iOS", "linux"),
+)
+
+
 async def test_select_tab(
     widget,
     probe,

testbed/tests/widgets/test_passwordinput.py

@@ -2,6 +2,7 @@
 
 import toga
 
+from .conftest import build_cleanup_test
 from .properties import (  # noqa: F401
     test_alignment,
     test_background_color,
@@ -44,6 +45,9 @@ def verify_font_sizes():
     return False, True
 
 
+test_cleanup = build_cleanup_test(toga.PasswordInput, xfail_platforms=("android",))
+
+
 async def test_value_hidden(widget, probe):
     "Value should always be hidden in a PasswordInput"
     assert probe.value_hidden

testbed/tests/widgets/test_progressbar.py

@@ -2,6 +2,7 @@
 
 import toga
 
+from .conftest import build_cleanup_test
 from .properties import (  # noqa: F401
     test_enable_noop,
     test_flex_horizontal_widget_size,
@@ -19,6 +20,9 @@ async def widget():
     return toga.ProgressBar(max=100, value=5)
 
 
+test_cleanup = build_cleanup_test(toga.ProgressBar)
+
+
 async def test_start_stop_determinate(widget, probe):
     "A determinate progress bar can be started and stopped"
     # Widget should be initially stopped and determinate

testbed/tests/widgets/test_scrollcontainer.py

@@ -7,6 +7,7 @@
 from toga.colors import CORNFLOWERBLUE, REBECCAPURPLE, TRANSPARENT
 from toga.style.pack import COLUMN, ROW, Pack
 
+from .conftest import build_cleanup_test
 from .properties import (  # noqa: F401
     test_background_color,
     test_background_color_reset,
@@ -72,6 +73,14 @@ async def widget(content, on_scroll):
     )
 
 
+test_cleanup = build_cleanup_test(
+    # Pass a function here to prevent init of toga.Box() in a different thread than
+    # toga.ScrollContainer. This would raise a runtime error on Windows.
+    lambda: toga.ScrollContainer(content=toga.Box()),
+    xfail_platforms=("android", "iOS", "linux"),
+)
+
+
 async def test_clear_content(widget, probe, small_content):
     "Widget content can be cleared and reset"
     assert probe.document_width == probe.width - probe.scrollbar_inset