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

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"""Tests for local (dirty-tracked) re-rendering and measurement caching.

These exercise the incremental render path: a state change marks only

the owning component's subtree dirty, and

[`flush_dirty`][pythonnative.reconciler.Reconciler.flush_dirty]

re-renders just that subtree instead of the whole app. They also cover

the measurement cache that lets untouched leaves skip native

``measure_intrinsic`` calls across layout passes.

"""

from typing import Any, Dict, List, Tuple

from pythonnative.component import component

from pythonnative.components import ErrorBoundary

from pythonnative.element import Element

from pythonnative.hooks import create_context, use_context, use_state

from pythonnative.reconciler import Reconciler

from pythonnative.testing import FakeBackend as MockBackend

def _make_reconciler() -> Tuple[Reconciler, MockBackend]:

backend = MockBackend()

rec = Reconciler(backend)

# The screen host normally supplies this; tests drive flush_dirty by

# hand so a no-op trigger is enough.

rec.on_render_requested = lambda: None

return rec, backend

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

# Local re-render

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

def test_flush_dirty_rerenders_only_dirty_component() -> None:

render_counts = {"a": 0, "b": 0, "parent": 0}

setters: Dict[str, Any] = {}

@component

def child(name: str = "") -> Element:

render_counts[name] += 1

value, set_value = use_state(0)

setters[name] = set_value

return Element("Text", {"text": f"{name}:{value}"}, [])

@component

def parent() -> Element:

render_counts["parent"] += 1

return Element(

"Column",

{},

[child(name="a").with_key("a"), child(name="b").with_key("b")],

)

rec, _backend = _make_reconciler()

rec.mount(parent())

assert render_counts == {"a": 1, "b": 1, "parent": 1}

# Change only child "a"'s state.

setters["a"](1)

rec.flush_dirty()

assert render_counts["a"] == 2

assert render_counts["b"] == 1, "sibling component must not re-render"

assert render_counts["parent"] == 1, "ancestor must not re-render"

def test_flush_dirty_updates_only_the_changed_native_view() -> None:

setters: Dict[str, Any] = {}

@component

def child(name: str = "") -> Element:

value, set_value = use_state(0)

setters[name] = set_value

return Element("Text", {"text": f"{name}:{value}"}, [])

@component

def parent() -> Element:

return Element("Column", {}, [child(name="a").with_key("a"), child(name="b").with_key("b")])

rec, backend = _make_reconciler()

column = rec.mount(parent())

assert column.children[0].props["text"] == "a:0"

assert column.children[1].props["text"] == "b:0"

backend.ops.clear()

setters["a"](7)

rec.flush_dirty()

assert column.children[0].props["text"] == "a:7"

assert column.children[1].props["text"] == "b:0"

# Only the "a" Text view should have been updated.

updates = [op for op in backend.ops if op[0] == "update"]

assert len(updates) == 1

def test_flush_dirty_batches_multiple_dirty_components() -> None:

render_counts = {"a": 0, "b": 0}

setters: Dict[str, Any] = {}

@component

def child(name: str = "") -> Element:

render_counts[name] += 1

value, set_value = use_state(0)

setters[name] = set_value

return Element("Text", {"text": f"{name}:{value}"}, [])

@component

def parent() -> Element:

return Element("Column", {}, [child(name="a").with_key("a"), child(name="b").with_key("b")])

rec, _backend = _make_reconciler()

rec.mount(parent())

setters["a"](1)

setters["b"](1)

rec.flush_dirty()

assert render_counts == {"a": 2, "b": 2}

def test_flush_dirty_skips_descendant_already_covered_by_ancestor() -> None:

render_counts = {"outer": 0, "inner": 0}

setters: Dict[str, Any] = {}

@component

def inner() -> Element:

render_counts["inner"] += 1

value, set_inner = use_state(0)

setters["inner"] = set_inner

return Element("Text", {"text": f"inner:{value}"}, [])

@component

def outer() -> Element:

render_counts["outer"] += 1

value, set_outer = use_state(0)

setters["outer"] = set_outer

return Element("Column", {"text": str(value)}, [inner()])

rec, _backend = _make_reconciler()

rec.mount(outer())

assert render_counts == {"outer": 1, "inner": 1}

# Both dirty in the same pass; the ancestor re-render already

# re-renders the descendant, so inner runs exactly once more.

setters["outer"](1)

setters["inner"](1)

rec.flush_dirty()

assert render_counts["outer"] == 2

assert render_counts["inner"] == 2

def test_flush_dirty_preserves_provider_context() -> None:

theme = create_context("light")

seen: List[str] = []

setters: Dict[str, Any] = {}

@component

def consumer() -> Element:

t = use_context(theme)

seen.append(t)

_value, set_value = use_state(0)

setters["x"] = set_value

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

@component

def app() -> Element:

return theme.Provider("dark", consumer())

rec, _backend = _make_reconciler()

rec.mount(app())

assert seen[-1] == "dark"

# A purely local re-render of the consumer must still resolve the

# ancestor Provider's value (regression guard: without restoring the

# ancestor context stack this would read the "light" default).

setters["x"](1)

rec.flush_dirty()

assert seen[-1] == "dark"

def test_unmounted_component_setter_does_not_resurrect_subtree() -> None:

setters: Dict[str, Any] = {}

render_counts = {"child": 0}

@component

def child() -> Element:

render_counts["child"] += 1

value, set_value = use_state(0)

setters["child"] = set_value

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

@component

def parent(show: bool = True) -> Element:

return Element("Column", {}, [child()] if show else [])

rec, _backend = _make_reconciler()

rec.mount(parent(show=True))

assert render_counts["child"] == 1

stale_setter = setters["child"]

# Unmount the child via a full reconcile.

rec.reconcile(parent(show=False))

# A setter call from the now-unmounted child must be a safe no-op.

stale_setter(5)

rec.flush_dirty()

assert render_counts["child"] == 1

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

# Error boundaries during local re-render

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

def test_local_rerender_error_is_caught_by_ancestor_boundary() -> None:

setters: Dict[str, Any] = {}

@component

def risky() -> Element:

value, set_value = use_state(0)

setters["risky"] = set_value

if value > 0:

raise ValueError("boom")

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

@component

def app() -> Element:

return ErrorBoundary(risky(), fallback=lambda err: Element("Text", {"text": f"caught:{err}"}, []))

rec, _backend = _make_reconciler()

root = rec.mount(app())

assert root.props["text"] == "ok"

# The setter triggers a local re-render that throws; the enclosing

# ErrorBoundary must catch it and mount the fallback.

setters["risky"](1)

rec.flush_dirty()

assert rec.root.native_view.props["text"].startswith("caught:")

def test_local_rerender_error_without_boundary_propagates() -> None:

setters: Dict[str, Any] = {}

@component

def risky() -> Element:

value, set_value = use_state(0)

setters["risky"] = set_value

if value > 0:

raise ValueError("boom")

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

@component

def app() -> Element:

return Element("Column", {}, [risky()])

rec, _backend = _make_reconciler()

rec.mount(app())

setters["risky"](1)

try:

rec.flush_dirty()

raised = False

except ValueError:

raised = True

assert raised, "error with no boundary must propagate out of flush_dirty"

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

# Measurement caching

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

def test_measurement_cache_skips_unchanged_leaves_across_layout_passes() -> None:

rec, backend = _make_reconciler()

rec.mount(

Element(

"Column",

{},

[Element("Text", {"text": "a"}, []), Element("Text", {"text": "b"}, [])],

)

rec.set_viewport_size(300.0, 600.0)

assert len(backend.measure_calls) == 2, "each leaf measured once on first layout"

# A second layout pass over an unchanged tree must hit the cache.

rec._run_layout()

assert len(backend.measure_calls) == 2, "unchanged leaves must not re-measure"

def test_measurement_cache_invalidated_only_for_rerendered_leaf() -> None:

setters: Dict[str, Any] = {}

@component

def child(name: str = "") -> Element:

value, set_value = use_state(0)

setters[name] = set_value

return Element("Text", {"text": f"{name}:{value}"}, [])

@component

def parent() -> Element:

return Element("Column", {}, [child(name="a").with_key("a"), child(name="b").with_key("b")])

rec, backend = _make_reconciler()

rec.mount(parent())

rec.set_viewport_size(300.0, 600.0)

a_view = rec.root.native_view.children[0]

b_view = rec.root.native_view.children[1]

assert sorted(backend.measure_calls) == sorted([a_view.id, b_view.id])

backend.measure_calls.clear()

setters["a"](1)

rec.flush_dirty()

# Only the re-rendered leaf produced a new Element identity, so only

# it is re-measured; the untouched sibling stays cached.

assert a_view.id in backend.measure_calls

assert b_view.id not in backend.measure_calls

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

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