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"""Tests for screen-host lifecycle behavior (``pythonnative.hosts``).
Off-device the host class is the headless ``ScreenHost``; these tests
drive it against a ``FakeBackend`` installed as the process registry.
The on-device host is covered by ``test_bridge.py`` through a
``FakeTransport``.
"""
import os
import sys
import types
from pathlib import Path
from typing import Any, Iterator, List, Optional, cast
import pytest
from pythonnative import diagnostics
from pythonnative.bridge import set_transport
from pythonnative.bridge.fake import FakeTransport
from pythonnative.component import component
from pythonnative.element import Element
from pythonnative.hooks import use_back_handler, use_effect, use_state
from pythonnative.hosts import create_screen, import_component
from pythonnative.native_views import set_backend
from pythonnative.testing import FakeBackend, FakeView, settle
@pytest.fixture
def backend(monkeypatch: pytest.MonkeyPatch) -> Iterator[FakeBackend]:
"""Install a ``FakeBackend`` as the registry the host mounts into."""
fake = FakeBackend()
set_backend(fake)
transport = FakeTransport()
set_transport(transport)
from pythonnative.bridge import codec
from pythonnative.hosts.base import ScreenHost
monkeypatch.setattr(
ScreenHost,
"_show_error",
lambda self, payload: transport.call("Host", "show_error", codec.dumps({"call_id": 0, "args": payload})),
)
monkeypatch.setattr(
ScreenHost,
"_dismiss_error",
lambda self: transport.call("Host", "dismiss_error", codec.dumps({"call_id": 0, "args": {}})),
)
try:
yield fake
finally:
set_backend(None)
set_transport(None)
def _install_app_module(monkeypatch: pytest.MonkeyPatch, name: str, root: Any) -> str:
"""Register an in-memory module exposing ``root`` as its ``App``."""
module = types.ModuleType(name)
module.App = root # type: ignore[attr-defined]
monkeypatch.setitem(sys.modules, name, module)
return name
def _text_of(view: Optional[FakeView]) -> List[str]:
return [v.text for v in view.walk() if v.text is not None] if view is not None else []
def _write_screen(path: Path, text: str) -> None:
path.write_text(
"from pythonnative.component import component\n"
"from pythonnative.element import Element\n\n"
"@component\n"
"def MainPage():\n"
f" return Element('Text', {{'text': {text!r}}}, [])\n",
encoding="utf-8",
)
# ======================================================================
# Hot reload
# ======================================================================
def test_screen_reload_reimports_root_component(
tmp_path: Path,
monkeypatch: pytest.MonkeyPatch,
backend: FakeBackend,
) -> None:
package_dir = tmp_path / "reload_app"
package_dir.mkdir()
screen_path = package_dir / "screen.py"
_write_screen(screen_path, "before")
monkeypatch.syspath_prepend(os.fspath(tmp_path))
monkeypatch.setattr(sys, "dont_write_bytecode", True)
sys.modules.pop("reload_app.screen", None)
sys.modules.pop("reload_app", None)
host = create_screen("reload_app.screen.MainPage")
host.on_create()
assert _text_of(host.root_native_view) == ["before"]
_write_screen(screen_path, "after")
host.reload(["reload_app.screen"])
assert _text_of(host.root_native_view) == ["after"]
host.on_destroy()
# ======================================================================
# Lifecycle
# ======================================================================
def test_screen_host_on_destroy_unmounts_tree(monkeypatch: pytest.MonkeyPatch, backend: FakeBackend) -> None:
"""``on_destroy`` must unmount the reconciler: cleanups run, views die."""
cleanups: list = []
@component
def Root() -> Element:
use_effect(lambda: lambda: cleanups.append("cleaned"), [])
return Element("Text", {"text": "hi"}, [])
host = create_screen(_install_app_module(monkeypatch, "destroy_app", Root))
host.on_create()
assert host.reconciler is not None
assert backend.live_view_count() > 0
assert cleanups == []
host.on_destroy()
assert cleanups == ["cleaned"], "effect cleanup must run on destroy"
assert host.reconciler is None
assert host.root_native_view is None
assert backend.live_view_count() == 0
def test_screen_host_on_create_is_idempotent_across_view_recreation(
monkeypatch: pytest.MonkeyPatch, backend: FakeBackend
) -> None:
"""Android recreates a fragment's view on pop-back; the tree must persist."""
mounts: list = []
@component
def Root() -> Element:
use_effect(lambda: mounts.append("mounted"), [])
return Element("Text", {"text": "hi"}, [])
host = create_screen(_install_app_module(monkeypatch, "recreate_app", Root))
host.on_create()
reconciler, root = host.reconciler, host.root_native_view
host.on_create()
assert host.reconciler is reconciler
assert host.root_native_view is root
assert mounts == ["mounted"]
host.on_destroy()
def test_screen_host_focus_and_args(monkeypatch: pytest.MonkeyPatch, backend: FakeBackend) -> None:
"""``on_pause`` / ``on_resume`` drive focus listeners; ``set_args`` accepts JSON."""
@component
def Root() -> Element:
return Element("Text", {"text": "hi"}, [])
host = create_screen(_install_app_module(monkeypatch, "focus_app", Root), None, '{"pn_nav": {"routes": []}}')
assert host.args == {"pn_nav": {"routes": []}}
assert host.initial_navigation_state() is None, "an empty route list is not a navigation state"
host.set_args("not json")
assert host.args == {}
host.set_args({"k": 1})
assert host.args == {"k": 1}
seen: List[bool] = []
remove = host.add_focus_listener(seen.append)
host.on_create()
assert host.is_focused is True
host.on_pause()
host.on_pause()
host.on_resume()
assert seen == [False, True], "focus listeners fire once per transition"
remove()
host.on_pause()
assert seen == [False, True]
host.on_destroy()
def test_screen_host_on_back_pressed_routes_to_handlers(monkeypatch: pytest.MonkeyPatch, backend: FakeBackend) -> None:
"""``on_back_pressed`` consults ``use_back_handler`` subscribers."""
consume = {"value": True}
@component
def Root() -> Element:
_count, _set_count = use_state(0)
use_back_handler(lambda: consume["value"])
return Element("Text", {"text": "hi"}, [])
host = create_screen(_install_app_module(monkeypatch, "back_app", Root))
host.on_create()
assert host.on_back_pressed() is True
consume["value"] = False
assert host.on_back_pressed() is False
host.on_destroy()
assert host.on_back_pressed() is False, "destroyed host must decline back events"
# ======================================================================
# Viewport
# ======================================================================
def test_set_viewport_size_forwards_to_reconciler(monkeypatch: pytest.MonkeyPatch, backend: FakeBackend) -> None:
@component
def Root() -> Element:
return Element("Column", {}, [Element("Text", {"text": "hi"}, [])])
host = create_screen(_install_app_module(monkeypatch, "viewport_app", Root))
host.set_viewport_size(390, 844) # before mount: nothing to forward to
host.on_create()
assert host.reconciler is not None
assert backend.ops_of("set_frame") == [], "the headless host supplies no viewport, so no layout yet"
host.set_viewport_size(390, 844)
assert host.reconciler.viewport_size == (390.0, 844.0)
# The root's own frame is owned by the platform host; children get laid out to the viewport width.
text = host.root_native_view.find_first("Text")
assert text is not None and text.frame[2] == 390.0
host.set_viewport_size(0, 844)
assert host.reconciler.viewport_size == (390.0, 844.0), "non-positive sizes are ignored"
host.on_destroy()
@pytest.fixture
def _metrics() -> Iterator[None]:
from pythonnative import platform_metrics
def reset() -> None:
platform_metrics.reset_window_dimensions()
platform_metrics.reset_screen_dimensions()
platform_metrics.reset_keyboard_height()
platform_metrics.reset_safe_area_insets()
reset()
yield
reset()
def test_native_viewport_payload_publishes_density_and_screen(_metrics: None) -> None:
"""The host payload's scale, font_scale, screen_width, and screen_height land in platform_metrics."""
from pythonnative import platform_metrics
from pythonnative.hosts.native import _publish_metrics
assert _publish_metrics(
{
"width": 390,
"height": 700,
"scale": 3,
"font_scale": 1.25,
"screen_width": 390,
"screen_height": 844,
"keyboard_height": 144,
}
) == (390.0, 700.0)
window = platform_metrics.get_window_dimensions()
assert (window.width, window.height, window.scale, window.font_scale) == (390.0, 700.0, 3.0, 1.25)
screen = platform_metrics.get_screen_dimensions()
assert (screen.width, screen.height, screen.scale, screen.font_scale) == (390.0, 844.0, 3.0, 1.25)
assert platform_metrics.get_keyboard_height() == 144.0
def test_native_viewport_payload_falls_back_without_density_or_screen(_metrics: None) -> None:
"""A payload with only width and height keeps scale 1.0 and reports the window as the screen."""
from pythonnative import platform_metrics
from pythonnative.hosts.native import _publish_metrics
_publish_metrics({"width": 360, "height": 800, "scale": "3", "font_scale": None})
window = platform_metrics.get_window_dimensions()
assert window == platform_metrics.WindowDimensions(360.0, 800.0, 1.0, 1.0)
assert platform_metrics.get_screen_dimensions() == window
# A later payload without density keeps the density an earlier one reported.
_publish_metrics({"width": 360, "height": 800, "scale": 2.625, "font_scale": 1.1})
_publish_metrics({"width": 800, "height": 360})
window = platform_metrics.get_window_dimensions()
assert (window.width, window.scale, window.font_scale) == (800.0, 2.625, 1.1)
assert _publish_metrics("not a dict") == (0.0, 0.0)
# ======================================================================
# RedBox
# ======================================================================
def test_mount_error_shows_redbox_in_dev_mode(monkeypatch: pytest.MonkeyPatch, backend: FakeBackend) -> None:
monkeypatch.setattr(diagnostics, "_dev_mode", True)
@component
def Root() -> Element:
raise RuntimeError("kaboom")
host = create_screen(_install_app_module(monkeypatch, "redbox_app", Root))
host.on_create()
from pythonnative.bridge import get_transport
assert host._redbox_visible
payload = cast(FakeTransport, get_transport()).calls[-1][2]
assert "RuntimeError in mount: kaboom" == payload["title"]
assert "kaboom" in payload["trace"]
assert backend.live_view_count() == 0
host.clear_redbox()
assert not host._redbox_visible
host.on_destroy()
def test_render_error_shows_redbox_and_dismiss_restores_tree(
monkeypatch: pytest.MonkeyPatch, backend: FakeBackend
) -> None:
monkeypatch.setattr(diagnostics, "_dev_mode", True)
setter: dict = {}
@component
def Root() -> Element:
broken, set_broken = use_state(False)
setter["set"] = set_broken
if broken:
raise RuntimeError("render broke")
return Element("Text", {"text": "fine"}, [])
host = create_screen(_install_app_module(monkeypatch, "redbox_render_app", Root))
host.on_create()
assert not host._redbox_visible
assert _text_of(host.root_native_view) == ["fine"]
setter["set"](True)
settle()
from pythonnative.bridge import get_transport
assert host._redbox_visible
assert "RuntimeError in render" in cast(FakeTransport, get_transport()).calls[-1][2]["title"]
assert _text_of(host.root_native_view) == ["fine"]
assert backend.live_view_count() == 1
host.clear_redbox()
assert not host._redbox_visible
host.on_destroy()
def test_mount_error_propagates_outside_dev_mode(monkeypatch: pytest.MonkeyPatch, backend: FakeBackend) -> None:
monkeypatch.setattr(diagnostics, "_dev_mode", False)
@component
def Root() -> Element:
raise RuntimeError("kaboom")
host = create_screen(_install_app_module(monkeypatch, "redbox_off_app", Root))
with pytest.raises(RuntimeError, match="kaboom"):
host.on_create()
assert not host._redbox_visible
host.on_destroy()
# ======================================================================
# Component resolution
# ======================================================================
def test_import_component_propagates_real_dependency_errors(
tmp_path: Path,
monkeypatch: pytest.MonkeyPatch,
) -> None:
"""A failing import *inside* the app must not be masked.
Regression: ``import_component`` caught every ``ModuleNotFoundError``
and reported a generic "could not resolve component", hiding the real
cause (e.g. a dependency the developer forgot to install). The actual
error must propagate, while a genuinely absent path still yields the
friendly resolve error. This is what makes ``pn preview`` surface
``No module named 'emoji'`` instead of a misleading message.
"""
pkg = tmp_path / "resolver_app"
pkg.mkdir()
(pkg / "__init__.py").write_text("", encoding="utf-8")
(pkg / "good.py").write_text("def App():\n return None\n\ndef Other():\n return None\n", encoding="utf-8")
(pkg / "bad.py").write_text(
"import a_dependency_that_is_not_installed_xyz\n\ndef App():\n return None\n",
encoding="utf-8",
)
monkeypatch.syspath_prepend(os.fspath(tmp_path))
monkeypatch.setattr(sys, "dont_write_bytecode", True)
for name in ("resolver_app", "resolver_app.good", "resolver_app.bad"):
sys.modules.pop(name, None)
# A resolvable module returns its ``App``; a dotted path returns the named attribute.
assert import_component("resolver_app.good").__name__ == "App"
assert import_component("resolver_app.good.Other").__name__ == "Other"
# The module exists but imports a missing dependency: the real
# ``ModuleNotFoundError`` (naming that dependency) must propagate.
with pytest.raises(ModuleNotFoundError) as excinfo:
import_component("resolver_app.bad")
assert excinfo.value.name == "a_dependency_that_is_not_installed_xyz"
# A genuinely absent path still gives the friendly resolve error.
with pytest.raises(ImportError, match="Could not resolve component"):
import_component("resolver_app.nope_does_not_exist")