pythonnative/tests/test_hosts.py at v0.41.0 · pythonnative/pythonnative · GitHub

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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

import pytest

from pythonnative import diagnostics

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 ScreenHost, create_screen, import_component

from pythonnative.native_views import set_registry

from pythonnative.testing import FakeBackend, FakeView

@pytest.fixture

def backend() -> Iterator[FakeBackend]:

"""Install a ``FakeBackend`` as the registry the host mounts into."""

fake = FakeBackend()

set_registry(fake)

try:

yield fake

finally:

set_registry(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_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"

def test_every_host_class_exposes_on_layout() -> None:

"""Regression: every host class must accept an ``on_layout`` callback.

The iOS template forwards ``viewDidLayoutSubviews`` as

``on_layout`` so the screen host can re-push the safe-area-aware

viewport size; missing the method on the base or native classes

would raise ``AttributeError`` at runtime.

"""

from pythonnative.hosts.native import NativeScreenHost

for host_class in (ScreenHost, NativeScreenHost):

assert callable(getattr(host_class, "on_layout", None))

def test_screen_host_on_layout_is_idempotent(monkeypatch: pytest.MonkeyPatch, backend: FakeBackend) -> None:

@component

def Root() -> Element:

return Element("Text", {"text": "hi"}, [])

host = create_screen(_install_app_module(monkeypatch, "layout_app", Root))

host.on_create()

host.on_layout()

assert _text_of(host.root_native_view) == ["hi"]

host.on_destroy()

# ======================================================================

# 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()

# ======================================================================

# 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()

assert host._redbox_reconciler is not None

overlay = _text_of(host._redbox_root)

assert "RuntimeError in mount" in overlay

assert "kaboom" in overlay

host.clear_redbox()

assert host._redbox_reconciler is None

assert host._redbox_root is None

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 host._redbox_reconciler is None

assert _text_of(host.root_native_view) == ["fine"]

setter["set"](True)

assert host._redbox_reconciler is not None

assert "RuntimeError in render" in _text_of(host._redbox_root)

dismiss = host._redbox_root.find_first("Button")

assert dismiss is not None and dismiss.text == "Dismiss"

host.clear_redbox()

assert host._redbox_reconciler is None

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 host._redbox_reconciler is None

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")

pythonnative/tests/test_hosts.py at v0.41.0 · pythonnative/pythonnative · GitHub

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