test: wait for the OLM wizard to finish mounting before leaving it

tests/ui/test_olm_view.py

@@ -27,7 +27,7 @@
 from korvid.ui.widgets.resource_table import ResourceTable
 from tests.app_factory import build_test_app
 
-from .waits import until
+from .waits import screen_ready, until
 
 _PODS_META = ResourceMeta("Pod", "pods", "", "v1", True, ("po",))
 PKG_META = ResourceMeta("PackageManifest", "packagemanifests", PACKAGES_GROUP, "v1", True)
@@ -356,9 +356,7 @@ async def test_install_key_walks_wizard_confirm_and_creates_subscription(
         table = app.query_one(ResourceTable)
         await until(pilot, lambda: table.row_count == 1, label="package listed")
         await pilot.press("I")
-        await until(
-            pilot, lambda: isinstance(app.screen, OperatorInstallPrompt), label="wizard open"
-        )
+        await until(pilot, lambda: screen_ready(app, OperatorInstallPrompt), label="wizard open")
         await pilot.press("enter")  # accept defaults: operators/stable/Automatic
         await until(pilot, lambda: isinstance(app.screen, ConfirmScreen), label="confirm open")
         body = app.screen.query_one(".confirm-operation").render()
@@ -595,9 +593,7 @@ async def test_install_fetches_manifest_by_canonical_view_kind(tmp_path: Path) -
         table = app.query_one(ResourceTable)
         await until(pilot, lambda: table.row_count == 1, label="package listed")
         await pilot.press("I")
-        await until(
-            pilot, lambda: isinstance(app.screen, OperatorInstallPrompt), label="wizard open"
-        )
+        await until(pilot, lambda: screen_ready(app, OperatorInstallPrompt), label="wizard open")
         assert fetch_log == [qualified]
 
 
@@ -675,9 +671,7 @@ async def test_install_wizard_prefills_default_namespace_with_zero_config(
         table = app.query_one(ResourceTable)
         await until(pilot, lambda: table.row_count == 1, label="package listed")
         await pilot.press("I")
-        await until(
-            pilot, lambda: isinstance(app.screen, OperatorInstallPrompt), label="wizard open"
-        )
+        await until(pilot, lambda: screen_ready(app, OperatorInstallPrompt), label="wizard open")
         ns_input = app.screen.query_one("#install-namespace")
         assert getattr(ns_input, "value", "") == "default"
 
@@ -729,9 +723,7 @@ async def record_check(
         table = app.query_one(ResourceTable)
         await until(pilot, lambda: table.row_count == 1, label="package listed")
         await pilot.press("I")
-        await until(
-            pilot, lambda: isinstance(app.screen, OperatorInstallPrompt), label="wizard open"
-        )
+        await until(pilot, lambda: screen_ready(app, OperatorInstallPrompt), label="wizard open")
         await pilot.press("enter")
         await until(pilot, lambda: bool(checks), label="permission pre-check ran")
         assert checks[0] == ("create", "subscriptions", "")
@@ -761,7 +753,7 @@ async def test_the_controller_routes_the_install_key_to_the_package_wizard(
         await app._olm.install_selected()
         await until(
             pilot,
-            lambda: isinstance(app.screen, OperatorInstallPrompt),
+            lambda: screen_ready(app, OperatorInstallPrompt),
             label="install wizard",
         )
         assert rec.calls == []

tests/ui/test_waits.py

@@ -3,8 +3,11 @@
 from __future__ import annotations
 
 import pytest
+from textual.app import App, ComposeResult
+from textual.screen import ModalScreen
+from textual.widgets import Select
 
-from .waits import WaitTimeout, until
+from .waits import WaitTimeout, screen_ready, until
 
 
 class _FakePilot:
@@ -50,3 +53,50 @@ async def test_until_timeout_is_not_an_assertion_error() -> None:
     with pytest.raises(WaitTimeout, match=r"condition not met within 0\.05s") as caught:
         await until(pilot, lambda: False, timeout=0.05)
     assert not isinstance(caught.value, AssertionError)
+
+
+class _Node:
+    def __init__(self, *, mounted: bool = True, children: tuple[_Node, ...] = ()) -> None:
+        self.is_mounted = mounted
+        self.children = children
+
+    def query(self, selector: str) -> tuple[_Node, ...]:
+        assert selector == "*"
+        return self.children
+
+
+class _Prompt(_Node):
+    pass
+
+
+class _App:
+    def __init__(self, screen: _Node) -> None:
+        self.screen = screen
+
+
+@pytest.mark.parametrize(
+    ("screen", "ready"),
+    [
+        pytest.param(_Node(), False, id="another screen"),
+        pytest.param(_Prompt(mounted=False), False, id="screen still mounting"),
+        pytest.param(
+            _Prompt(children=(_Node(), _Node(mounted=False))), False, id="a widget still mounting"
+        ),
+        pytest.param(_Prompt(children=(_Node(), _Node())), True, id="every widget mounted"),
+    ],
+)
+def test_screen_ready_waits_for_the_screen_and_every_widget(screen: _Node, ready: bool) -> None:
+    assert screen_ready(_App(screen), _Prompt) is ready
+
+
+async def test_screen_ready_holds_only_once_a_select_has_mounted() -> None:
+    class Prompt(ModalScreen[None]):
+        def compose(self) -> ComposeResult:
+            yield Select([("stable", "stable"), ("fast", "fast")], value="stable")
+
+    app = App[None]()
+    async with app.run_test() as pilot:
+        app.push_screen(Prompt())
+        await until(pilot, lambda: screen_ready(app, Prompt), label="prompt ready")
+
+        assert app.screen.query_one(Select).is_mounted

tests/ui/test_write_confirm_characterization.py

@@ -83,7 +83,7 @@
 from .test_resize_flow import ResizeRecorder
 from .test_resize_flow import make_app as make_resize_app
 from .test_write_ops import Recorder, _edit_fixtures, _to_view, make_app
-from .waits import until
+from .waits import screen_ready, until
 
 
 async def _row_listed(pilot, kind: str) -> None:  # type: ignore[no-untyped-def]  # Pilot's app type isn't exposed
@@ -266,9 +266,7 @@ async def test_install_cancelled_when_catalog_entry_changes_during_approval(
         table = app.query_one(ResourceTable)
         await until(pilot, lambda: table.row_count == 1, label="package listed")
         await pilot.press("I")
-        await until(
-            pilot, lambda: isinstance(app.screen, OperatorInstallPrompt), label="wizard open"
-        )
+        await until(pilot, lambda: screen_ready(app, OperatorInstallPrompt), label="wizard open")
         await pilot.press("enter")  # accept defaults
         await until(pilot, lambda: isinstance(app.screen, ConfirmScreen), label="confirm open")
         # Same name, different incarnation lands while the dialog is open.

tests/ui/waits.py

@@ -54,3 +54,17 @@ async def until(
     if cond():
         return
     raise WaitTimeout(f"{label} not met within {timeout}s")
+
+
+def screen_ready(app: Any, screen_type: type) -> bool:
+    """Whether `app` shows a `screen_type` whose every widget has finished mounting.
+
+    A screen is current as soon as it is pushed, before its widgets run their
+    Mount handlers. A test that leaves `run_test` at that point can tear a
+    widget down mid-handler: Textual's `Select` looks up its overlay in
+    `_on_mount`, and fails if the overlay is already gone (#504).
+    """
+    if not isinstance(app.screen, screen_type):
+        return False
+    screen: Any = app.screen
+    return bool(screen.is_mounted) and all(widget.is_mounted for widget in screen.query("*"))