pythonnative/tests/test_suspense.py at preview-api-reference-fix · andevsr/pythonnative · GitHub

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"""Unit tests for async components, Suspense, use_resource, and lazy."""

from __future__ import annotations

import asyncio

import time

from typing import Any

import pytest

from fake_backend import FakeBackend, FakeView

from pythonnative.components import ErrorBoundary, Suspense, Text, View

from pythonnative.element import Element

from pythonnative.hooks import component, use_resource, use_state

from pythonnative.reconciler import Reconciler

from pythonnative.runtime import create_future, drain, resolve_future

from pythonnative.suspense import CoroDriver, Suspend, lazy, start_resource

def _settle(rec: Reconciler, predicate: Any, timeout: float = 2.0) -> bool:

"""Pump the framework loop and flush renders until ``predicate`` holds."""

deadline = time.monotonic() + timeout

while time.monotonic() < deadline:

drain(timeout=0.05)

rec.flush_dirty()

if predicate():

return True

return False

def _texts(backend: FakeBackend) -> list:

"""Every live Text view's text prop, in creation order."""

return [v.props.get("text") for v in backend.views.values() if v.type_name == "Text"]

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

# CoroDriver

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

def test_coro_driver_completes_synchronously_without_awaits() -> None:

async def body() -> int:

return 5

driver = CoroDriver(body())

driver.start()

assert driver.done

assert driver.result() == 5

def test_coro_driver_resolves_done_futures_inline() -> None:

future = create_future()

resolve_future(future, "ready")

drain()

async def body() -> str:

return await future

driver = CoroDriver(body())

driver.start()

assert driver.done

assert driver.result() == "ready"

def test_coro_driver_parks_on_pending_future_then_resumes() -> None:

future = create_future()

seen: list = []

async def body() -> str:

value = await future

seen.append(value)

return value

driver = CoroDriver(body())

driver.start()

assert not driver.done

assert seen == []

resolve_future(future, "later")

drain(until=lambda: driver.done)

assert driver.done

assert driver.result() == "later"

assert seen == ["later"]

def test_coro_driver_supports_asyncio_sleep_in_sync_step() -> None:

"""Steps outside the loop still satisfy ``get_running_loop()`` callers.

``asyncio.sleep`` (and anything else using ``get_running_loop()``

internally) must work inside an ``async def`` component body even

when the first step runs synchronously during mount, before the

guest loop has ever run. Regression test: this raised

``RuntimeError: no running event loop``.

"""

async def body() -> str:

await asyncio.sleep(0.001)

return "slept"

driver = CoroDriver(body())

driver.start()

assert not driver.done

drain(until=lambda: driver.done)

assert driver.done

assert driver.result() == "slept"

def test_coro_driver_captures_exception() -> None:

async def body() -> None:

raise ValueError("bad")

driver = CoroDriver(body())

driver.start()

assert driver.done

assert isinstance(driver.exception(), ValueError)

def test_coro_driver_cancel() -> None:

future = create_future()

cancelled: list = []

async def body() -> None:

try:

await future

except asyncio.CancelledError:

cancelled.append(True)

raise

driver = CoroDriver(body())

driver.start()

assert driver.cancel()

assert driver.done

assert driver.cancelled()

assert cancelled == [True]

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

# Resource / start_resource

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

def test_start_resource_sync_fetcher_is_ready_immediately() -> None:

resource = start_resource(lambda: 42)

assert resource.ready

assert resource.read() == 42

def test_resource_read_suspends_while_pending() -> None:

future = create_future()

async def fetch() -> str:

return await future

resource = start_resource(fetch)

assert not resource.ready

with pytest.raises(Suspend):

resource.read()

resolve_future(future, "data")

drain(until=lambda: resource.ready)

assert resource.read() == "data"

def test_resource_read_reraises_fetcher_error() -> None:

async def fetch() -> None:

raise RuntimeError("fetch failed")

resource = start_resource(fetch)

assert resource.ready

with pytest.raises(RuntimeError, match="fetch failed"):

resource.read()

def test_resource_is_awaitable() -> None:

from pythonnative.runtime import run_blocking

async def fetch() -> int:

await asyncio.sleep(0)

return 9

resource = start_resource(fetch)

async def consume() -> int:

return await resource

assert run_blocking(consume(), timeout=2.0) == 9

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

# Async components

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

def test_async_component_without_pending_awaits_renders_synchronously() -> None:

@component

async def Hello() -> Element:

return Text("hi from async")

backend = FakeBackend()

rec = Reconciler(backend)

rec.mount(Hello())

assert "hi from async" in _texts(backend)

def test_async_component_suspends_without_boundary_raises() -> None:

future = create_future()

@component

async def Blocked() -> Element:

return Text(await future)

rec = Reconciler(FakeBackend())

with pytest.raises(RuntimeError, match="Suspense"):

rec.mount(Blocked())

def test_async_component_with_suspense_shows_fallback_then_content() -> None:

future = create_future()

@component

async def Greeting() -> Element:

text = await future

return Text(text)

backend = FakeBackend()

rec = Reconciler(backend)

rec.mount(Suspense(Greeting(), fallback=Text("loading...")))

assert _texts(backend) == ["loading..."]

resolve_future(future, "hello async")

assert _settle(rec, lambda: _texts(backend) == ["hello async"])

def test_sync_component_reading_resource_under_suspense() -> None:

future = create_future()

@component

def Profile() -> Element:

name = use_resource(lambda: _wait(future), []).read()

return Text(f"name: {name}")

backend = FakeBackend()

rec = Reconciler(backend)

rec.mount(Suspense(Profile(), fallback=Text("spinner")))

assert _texts(backend) == ["spinner"]

resolve_future(future, "Ada")

assert _settle(rec, lambda: _texts(backend) == ["name: Ada"])

async def _wait(future: Any) -> Any:

return await future

def test_suspense_retry_reuses_cached_resource() -> None:

"""The suspended component's hook state survives the fallback

round-trip, so its resource is fetched exactly once."""

fetches: list = []

future = create_future()

async def fetch() -> str:

fetches.append(1)

return await future

@component

def Data() -> Element:

value = use_resource(fetch, []).read()

return Text(value)

backend = FakeBackend()

rec = Reconciler(backend)

rec.mount(Suspense(Data(), fallback=Text("...")))

assert len(fetches) == 1

resolve_future(future, "cached")

assert _settle(rec, lambda: _texts(backend) == ["cached"])

assert len(fetches) == 1

def test_suspense_sibling_state_survives_suspension() -> None:

"""Siblings that rendered before the suspender are salvaged: their

resources aren't refetched on the boundary's retry."""

sibling_fetches: list = []

future = create_future()

@component

def FastSibling() -> Element:

value = use_resource(lambda: _fetch_fast(sibling_fetches), []).read()

return Text(value)

@component

def SlowChild() -> Element:

value = use_resource(lambda: _wait(future), []).read()

return Text(value)

backend = FakeBackend()

rec = Reconciler(backend)

rec.mount(

Suspense(

View(FastSibling(), SlowChild()),

fallback=Text("waiting"),

)

assert _texts(backend) == ["waiting"]

assert len(sibling_fetches) == 1

resolve_future(future, "slow done")

assert _settle(rec, lambda: sorted(_texts(backend)) == ["fast done", "slow done"])

assert len(sibling_fetches) == 1

async def _fetch_fast(log: list) -> str:

log.append(1)

return "fast done"

def test_update_suspension_keeps_previous_content() -> None:

"""A mounted component that suspends on a state-driven update keeps

its old content on screen (no fallback flash) and re-renders when

the new data arrives."""

futures = {0: create_future(), 1: create_future()}

resolve_future(futures[0], "page zero")

drain()

setters: list = []

@component

def Page() -> Element:

page, set_page = use_state(0)

setters.append(set_page)

value = use_resource(lambda: _wait(futures[page]), [page]).read()

return Text(value)

backend = FakeBackend()

rec = Reconciler(backend)

rec.mount(Suspense(Page(), fallback=Text("first load")))

drain()

rec.flush_dirty()

assert _texts(backend) == ["page zero"]

# Flip to page 1, whose data is pending: old content must stay.

setters[-1](1)

rec.flush_dirty()

drain(timeout=0.1)

rec.flush_dirty()

assert _texts(backend) == ["page zero"]

resolve_future(futures[1], "page one")

assert _settle(rec, lambda: _texts(backend) == ["page one"])

def test_nested_suspense_inner_boundary_catches() -> None:

future = create_future()

@component

async def Inner() -> Element:

return Text(await future)

backend = FakeBackend()

rec = Reconciler(backend)

rec.mount(

Suspense(

Text("outer content"),

Suspense(Inner(), fallback=Text("inner loading")),

fallback=Text("outer loading"),

)

assert sorted(_texts(backend)) == ["inner loading", "outer content"]

resolve_future(future, "inner ready")

assert _settle(rec, lambda: sorted(_texts(backend)) == ["inner ready", "outer content"])

def test_async_component_error_reaches_error_boundary() -> None:

@component

async def Explodes() -> Element:

await asyncio.sleep(0)

raise ValueError("async crash")

backend = FakeBackend()

rec = Reconciler(backend)

rec.mount(

ErrorBoundary(

Suspense(Explodes(), fallback=Text("loading")),

fallback=lambda err: Text(f"caught: {err}"),

)

assert _texts(backend) == ["loading"]

assert _settle(rec, lambda: _texts(backend) == ["caught: async crash"])

def test_resource_error_reaches_error_boundary() -> None:

@component

def Reads() -> Element:

return Text(use_resource(_failing_fetch, []).read())

backend = FakeBackend()

rec = Reconciler(backend)

rec.mount(

ErrorBoundary(

Suspense(Reads(), fallback=Text("loading")),

fallback=lambda err: Text("recovered"),

)

assert _texts(backend) == ["recovered"]

async def _failing_fetch() -> None:

raise RuntimeError("nope")

def test_suspense_without_fallback_is_transparent() -> None:

"""A boundary with no fallback lets the suspension propagate to the

next boundary up."""

future = create_future()

@component

async def Pending() -> Element:

return Text(await future)

backend = FakeBackend()

rec = Reconciler(backend)

rec.mount(

Suspense(

Suspense(Pending()),

fallback=Text("outer catches"),

)

assert _texts(backend) == ["outer catches"]

resolve_future(future, "done")

assert _settle(rec, lambda: _texts(backend) == ["done"])

def test_suspense_fallback_can_be_a_callable() -> None:

future = create_future()

@component

async def Pending() -> Element:

return Text(await future)

backend = FakeBackend()

rec = Reconciler(backend)

rec.mount(Suspense(Pending(), fallback=lambda: Text("lazy fallback")))

assert _texts(backend) == ["lazy fallback"]

def test_unmount_while_suspended_cancels_cleanly() -> None:

future = create_future()

@component

async def Pending() -> Element:

return Text(await future)

backend = FakeBackend()

rec = Reconciler(backend)

rec.mount(Suspense(Pending(), fallback=Text("loading")))

rec.unmount()

assert backend.live_view_count() == 0

# Late resolution must not blow up or resurrect the tree.

resolve_future(future, "too late")

drain()

rec.flush_dirty()

assert backend.live_view_count() == 0

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

# lazy

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

def test_lazy_sync_loader_renders_without_suspending() -> None:

@component

def Real(label: str = "") -> Element:

return Text(f"real: {label}")

Lazy = lazy(lambda: Real)

backend = FakeBackend()

rec = Reconciler(backend)

rec.mount(Suspense(Lazy(label="x"), fallback=Text("loading")))

assert _texts(backend) == ["real: x"]

def test_lazy_async_loader_suspends_then_renders() -> None:

future = create_future()

@component

def Real() -> Element:

return Text("loaded component")

async def load() -> Any:

await future

return Real

Lazy = lazy(load)

backend = FakeBackend()

rec = Reconciler(backend)

rec.mount(Suspense(Lazy(), fallback=Text("code loading")))

assert _texts(backend) == ["code loading"]

resolve_future(future, None)

assert _settle(rec, lambda: _texts(backend) == ["loaded component"])

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

# use_resource dependency semantics

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

def test_use_resource_refetches_on_deps_change() -> None:

fetched_for: list = []

@component

def Item(item_id: int = 0) -> Element:

resource = use_resource(lambda: _fetch_item(item_id, fetched_for), [item_id])

return Text(str(resource.read()))

backend = FakeBackend()

rec = Reconciler(backend)

rec.mount(Suspense(Item(item_id=1), fallback=Text("...")))

drain()

rec.flush_dirty()

assert fetched_for == [1]

rec.reconcile(Suspense(Item(item_id=2), fallback=Text("...")))

drain()

rec.flush_dirty()

assert fetched_for == [1, 2]

rec.reconcile(Suspense(Item(item_id=2), fallback=Text("...")))

drain()

assert fetched_for == [1, 2]

async def _fetch_item(item_id: int, log: list) -> int:

log.append(item_id)

return item_id * 10

# Keep a reference so linters don't flag the FakeView import (used in

# type comments / debugging helpers).

_ = FakeView

pythonnative/tests/test_suspense.py at preview-api-reference-fix · andevsr/pythonnative · GitHub

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