Concurrent Renders

.github/workflows/.hatch-run.yml

@@ -1,59 +1,59 @@
 name: hatch-run
 
 on:
-  workflow_call:
-    inputs:
-      job-name:
-        required: true
-        type: string
-      hatch-run:
-        required: true
-        type: string
-      runs-on-array:
-        required: false
-        type: string
-        default: '["ubuntu-latest"]'
-      python-version-array:
-        required: false
-        type: string
-        default: '["3.x"]'
-      node-registry-url:
-        required: false
-        type: string
-        default: ""
-    secrets:
-      node-auth-token:
-        required: false
-      pypi-username:
-        required: false
-      pypi-password:
-        required: false
+    workflow_call:
+        inputs:
+            job-name:
+                required: true
+                type: string
+            hatch-run:
+                required: true
+                type: string
+            runs-on-array:
+                required: false
+                type: string
+                default: '["ubuntu-latest"]'
+            python-version-array:
+                required: false
+                type: string
+                default: '["3.11"]'
+            node-registry-url:
+                required: false
+                type: string
+                default: ""
+        secrets:
+            node-auth-token:
+                required: false
+            pypi-username:
+                required: false
+            pypi-password:
+                required: false
 
 jobs:
-  hatch:
-    name: ${{ format(inputs.job-name, matrix.python-version, matrix.runs-on) }}
-    strategy:
-      matrix:
-        python-version: ${{ fromJson(inputs.python-version-array) }}
-        runs-on: ${{ fromJson(inputs.runs-on-array) }}
-    runs-on: ${{ matrix.runs-on }}
-    steps:
-      - uses: actions/checkout@v2
-      - uses: actions/setup-node@v2
-        with:
-          node-version: "14.x"
-          registry-url: ${{ inputs.node-registry-url }}
-      - name: Pin NPM Version
-        run: npm install -g npm@8.19.3
-      - name: Use Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
-        with:
-          python-version: ${{ matrix.python-version }}
-      - name: Install Python Dependencies
-        run: pip install hatch poetry
-      - name: Run Scripts
-        env:
-          NODE_AUTH_TOKEN: ${{ secrets.node-auth-token }}
-          PYPI_USERNAME: ${{ secrets.pypi-username }}
-          PYPI_PASSWORD: ${{ secrets.pypi-password }}
-        run: hatch run ${{ inputs.hatch-run }}
+    hatch:
+        name: ${{ format(inputs.job-name, matrix.python-version, matrix.runs-on) }}
+        strategy:
+            matrix:
+                python-version: ${{ fromJson(inputs.python-version-array) }}
+                runs-on: ${{ fromJson(inputs.runs-on-array) }}
+        runs-on: ${{ matrix.runs-on }}
+        steps:
+            - uses: actions/checkout@v2
+            - uses: actions/setup-node@v2
+              with:
+                  node-version: "14.x"
+                  registry-url: ${{ inputs.node-registry-url }}
+            - name: Pin NPM Version
+              run: npm install -g npm@8.19.3
+            - name: Use Python ${{ matrix.python-version }}
+              uses: actions/setup-python@v2
+              with:
+                  python-version: ${{ matrix.python-version }}
+            - name: Install Python Dependencies
+              run: pip install hatch poetry
+            - name: Run Scripts
+              env:
+                  NODE_AUTH_TOKEN: ${{ secrets.node-auth-token }}
+                  PYPI_USERNAME: ${{ secrets.pypi-username }}
+                  PYPI_PASSWORD: ${{ secrets.pypi-password }}
+              run: hatch run ${{ inputs.hatch-run }}

docs/source/about/changelog.rst

@@ -28,6 +28,13 @@ Unreleased
 - :pull:`1118` - `module_from_template` is broken with a recent release of `requests`
 - :pull:`1131` - `module_from_template` did not work when using Flask backend
 
+**Added**
+
+- :pull:`1165` - Allow concurrent renders of distinct components - enable this
+  experimental feature by setting `REACTPY_FEATURE_CONCURRENT_RENDERING=true`.
+  This should improve the overall responsiveness of your app, particularly when
+  handling larger renders that would otherwise block faster renders from being
+  processed.
 
 v1.0.2
 ------

src/py/reactpy/reactpy/_option.py

@@ -68,6 +68,10 @@ def current(self) -> _O:
     def current(self, new: _O) -> None:
         self.set_current(new)
 
+    @current.deleter
+    def current(self) -> None:
+        self.unset()
+
     def subscribe(self, handler: Callable[[_O], None]) -> Callable[[_O], None]:
         """Register a callback that will be triggered when this option changes"""
         if not self.mutable:
@@ -123,7 +127,8 @@ def unset(self) -> None:
             msg = f"{self} cannot be modified after initial load"
             raise TypeError(msg)
         old = self.current
-        delattr(self, "_current")
+        if hasattr(self, "_current"):
+            delattr(self, "_current")
         if self.current != old:
             for sub_func in self._subscribers:
                 sub_func(self.current)

src/py/reactpy/reactpy/backend/hooks.py

@@ -4,7 +4,8 @@
 from typing import Any
 
 from reactpy.backend.types import Connection, Location
-from reactpy.core.hooks import Context, create_context, use_context
+from reactpy.core.hooks import create_context, use_context
+from reactpy.core.types import Context
 
 # backend implementations should establish this context at the root of an app
 ConnectionContext: Context[Connection[Any] | None] = create_context(None)

src/py/reactpy/reactpy/config.py

@@ -80,3 +80,11 @@ def boolean(value: str | bool | int) -> bool:
     validator=float,
 )
 """A default timeout for testing utilities in ReactPy"""
+
+REACTPY_FEATURE_CONCURRENT_RENDERING = Option(
+    "REACTPY_CONCURRENT_RENDERING",
+    default=False,
+    mutable=True,
+    validator=boolean,
+)
+"""Whether to render components concurrently. This is currently an experimental feature."""

src/py/reactpy/reactpy/core/_life_cycle_hook.py

@@ -0,0 +1,220 @@
+from __future__ import annotations
+
+import logging
+from asyncio import Event, Task, create_task, gather
+from typing import Any, Callable, Protocol, TypeVar
+
+from anyio import Semaphore
+
+from reactpy.core._thread_local import ThreadLocal
+from reactpy.core.types import ComponentType, Context, ContextProviderType
+
+T = TypeVar("T")
+
+
+class EffectFunc(Protocol):
+    async def __call__(self, stop: Event) -> None:
+        ...
+
+
+logger = logging.getLogger(__name__)
+
+_HOOK_STATE: ThreadLocal[list[LifeCycleHook]] = ThreadLocal(list)
+
+
+def current_hook() -> LifeCycleHook:
+    """Get the current :class:`LifeCycleHook`"""
+    hook_stack = _HOOK_STATE.get()
+    if not hook_stack:
+        msg = "No life cycle hook is active. Are you rendering in a layout?"
+        raise RuntimeError(msg)
+    return hook_stack[-1]
+
+
+class LifeCycleHook:
+    """Defines the life cycle of a layout component.
+
+    Components can request access to their own life cycle events and state through hooks
+    while :class:`~reactpy.core.proto.LayoutType` objects drive drive the life cycle
+    forward by triggering events and rendering view changes.
+
+    Example:
+
+        If removed from the complexities of a layout, a very simplified full life cycle
+        for a single component with no child components would look a bit like this:
+
+        .. testcode::
+
+            from reactpy.core._life_cycle_hook import LifeCycleHook
+            from reactpy.core.hooks import current_hook
+
+            # this function will come from a layout implementation
+            schedule_render = lambda: ...
+
+            # --- start life cycle ---
+
+            hook = LifeCycleHook(schedule_render)
+
+            # --- start render cycle ---
+
+            component = ...
+            await hook.affect_component_will_render(component)
+            try:
+                # render the component
+                ...
+
+                # the component may access the current hook
+                assert current_hook() is hook
+
+                # and save state or add effects
+                current_hook().use_state(lambda: ...)
+
+                async def start_effect():
+                    ...
+
+                async def stop_effect():
+                    ...
+
+                current_hook().add_effect(start_effect, stop_effect)
+            finally:
+                await hook.affect_component_did_render()
+
+            # This should only be called after the full set of changes associated with a
+            # given render have been completed.
+            await hook.affect_layout_did_render()
+
+            # Typically an event occurs and a new render is scheduled, thus beginning
+            # the render cycle anew.
+            hook.schedule_render()
+
+
+            # --- end render cycle ---
+
+            hook.affect_component_will_unmount()
+            del hook
+
+            # --- end render cycle ---
+    """
+
+    __slots__ = (
+        "__weakref__",
+        "_context_providers",
+        "_current_state_index",
+        "_effect_funcs",
+        "_effect_stops",
+        "_effect_tasks",
+        "_render_access",
+        "_rendered_atleast_once",
+        "_schedule_render_callback",
+        "_scheduled_render",
+        "_state",
+        "component",
+    )
+
+    component: ComponentType
+
+    def __init__(
+        self,
+        schedule_render: Callable[[], None],
+    ) -> None:
+        self._context_providers: dict[Context[Any], ContextProviderType[Any]] = {}
+        self._schedule_render_callback = schedule_render
+        self._scheduled_render = False
+        self._rendered_atleast_once = False
+        self._current_state_index = 0
+        self._state: tuple[Any, ...] = ()
+        self._effect_funcs: list[EffectFunc] = []
+        self._effect_tasks: list[Task[None]] = []
+        self._effect_stops: list[Event] = []
+        self._render_access = Semaphore(1)  # ensure only one render at a time
+
+    def schedule_render(self) -> None:
+        if self._scheduled_render:
+            return None
+        try:
+            self._schedule_render_callback()
+        except Exception:
+            msg = f"Failed to schedule render via {self._schedule_render_callback}"
+            logger.exception(msg)
+        else:
+            self._scheduled_render = True
+
+    def use_state(self, function: Callable[[], T]) -> T:
+        if not self._rendered_atleast_once:
+            # since we're not initialized yet we're just appending state
+            result = function()
+            self._state += (result,)
+        else:
+            # once finalized we iterate over each succesively used piece of state
+            result = self._state[self._current_state_index]
+        self._current_state_index += 1
+        return result
+
+    def add_effect(self, effect_func: EffectFunc) -> None:
+        """Add an effect to this hook
+
+        A task to run the effect is created when the component is done rendering.
+        When the component will be unmounted, the event passed to the effect is
+        triggered and the task is awaited. The effect should eventually halt after
+        the event is triggered.
+        """
+        self._effect_funcs.append(effect_func)
+
+    def set_context_provider(self, provider: ContextProviderType[Any]) -> None:
+        self._context_providers[provider.type] = provider
+
+    def get_context_provider(
+        self, context: Context[T]
+    ) -> ContextProviderType[T] | None:
+        return self._context_providers.get(context)
+
+    async def affect_component_will_render(self, component: ComponentType) -> None:
+        """The component is about to render"""
+        await self._render_access.acquire()
+        self._scheduled_render = False
+        self.component = component
+        self.set_current()
+
+    async def affect_component_did_render(self) -> None:
+        """The component completed a render"""
+        self.unset_current()
+        self._rendered_atleast_once = True
+        self._current_state_index = 0
+        self._render_access.release()
+        del self.component
+
+    async def affect_layout_did_render(self) -> None:
+        """The layout completed a render"""
+        stop = Event()
+        self._effect_stops.append(stop)
+        self._effect_tasks.extend(create_task(e(stop)) for e in self._effect_funcs)
+        self._effect_funcs.clear()
+
+    async def affect_component_will_unmount(self) -> None:
+        """The component is about to be removed from the layout"""
+        for stop in self._effect_stops:
+            stop.set()
+        self._effect_stops.clear()
+        try:
+            await gather(*self._effect_tasks)
+        except Exception:
+            logger.exception("Error in effect")
+        finally:
+            self._effect_tasks.clear()
+
+    def set_current(self) -> None:
+        """Set this hook as the active hook in this thread
+
+        This method is called by a layout before entering the render method
+        of this hook's associated component.
+        """
+        hook_stack = _HOOK_STATE.get()
+        if hook_stack:
+            parent = hook_stack[-1]
+            self._context_providers.update(parent._context_providers)
+        hook_stack.append(self)
+
+    def unset_current(self) -> None:
+        """Unset this hook as the active hook in this thread"""
+        if _HOOK_STATE.get().pop() is not self:
+            raise RuntimeError("Hook stack is in an invalid state")  # nocov