from __future__ import annotations
import abc
from asyncio import (
FIRST_COMPLETED,
CancelledError,
Queue,
Task,
create_task,
get_running_loop,
wait,
)
from collections import Counter
from collections.abc import Sequence
from contextlib import AsyncExitStack
from logging import getLogger
from typing import (
Any,
Callable,
Generic,
NamedTuple,
NewType,
TypeVar,
cast,
)
from uuid import uuid4
from weakref import ref as weakref
from anyio import Semaphore
from typing_extensions import TypeAlias
from reactpy.config import (
REACTPY_ASYNC_RENDERING,
REACTPY_CHECK_VDOM_SPEC,
REACTPY_DEBUG_MODE,
)
from reactpy.core._life_cycle_hook import LifeCycleHook
from reactpy.core.types import (
ComponentType,
EventHandlerDict,
Key,
LayoutEventMessage,
LayoutUpdateMessage,
VdomChild,
VdomDict,
VdomJson,
)
from reactpy.core.vdom import validate_vdom_json
from reactpy.utils import Ref
logger = getLogger(__name__)
[docs]class Layout:
"""Responsible for "rendering" components. That is, turning them into VDOM."""
__slots__: tuple[str, ...] = (
"root",
"_event_handlers",
"_rendering_queue",
"_render_tasks",
"_render_tasks_ready",
"_root_life_cycle_state_id",
"_model_states_by_life_cycle_state_id",
)
if not hasattr(abc.ABC, "__weakref__"): # nocov
__slots__ += ("__weakref__",)
def __init__(self, root: ComponentType) -> None:
super().__init__()
if not isinstance(root, ComponentType):
msg = f"Expected a ComponentType, not {type(root)!r}."
raise TypeError(msg)
self.root = root
async def __aenter__(self) -> Layout:
# create attributes here to avoid access before entering context manager
self._event_handlers: EventHandlerDict = {}
self._render_tasks: set[Task[LayoutUpdateMessage]] = set()
self._render_tasks_ready: Semaphore = Semaphore(0)
self._rendering_queue: _ThreadSafeQueue[_LifeCycleStateId] = _ThreadSafeQueue()
root_model_state = _new_root_model_state(self.root, self._schedule_render_task)
self._root_life_cycle_state_id = root_id = root_model_state.life_cycle_state.id
self._model_states_by_life_cycle_state_id = {root_id: root_model_state}
self._schedule_render_task(root_id)
return self
async def __aexit__(self, *exc: Any) -> None:
root_csid = self._root_life_cycle_state_id
root_model_state = self._model_states_by_life_cycle_state_id[root_csid]
for t in self._render_tasks:
t.cancel()
try:
await t
except CancelledError:
pass
await self._unmount_model_states([root_model_state])
# delete attributes here to avoid access after exiting context manager
del self._event_handlers
del self._rendering_queue
del self._root_life_cycle_state_id
del self._model_states_by_life_cycle_state_id
[docs] async def deliver(self, event: LayoutEventMessage) -> None:
"""Dispatch an event to the targeted handler"""
# It is possible for an element in the frontend to produce an event
# associated with a backend model that has been deleted. We only handle
# events if the element and the handler exist in the backend. Otherwise
# we just ignore the event.
handler = self._event_handlers.get(event["target"])
if handler is not None:
try:
await handler.function(event["data"])
except Exception:
logger.exception(f"Failed to execute event handler {handler}")
else:
logger.info(
f"Ignored event - handler {event['target']!r} "
"does not exist or its component unmounted"
)
async def render(self) -> LayoutUpdateMessage:
if REACTPY_ASYNC_RENDERING.current:
return await self._parallel_render()
else: # nocov
return await self._serial_render()
async def _serial_render(self) -> LayoutUpdateMessage: # nocov
"""Await the next available render. This will block until a component is updated"""
while True:
model_state_id = await self._rendering_queue.get()
try:
model_state = self._model_states_by_life_cycle_state_id[model_state_id]
except KeyError:
logger.debug(
"Did not render component with model state ID "
f"{model_state_id!r} - component already unmounted"
)
else:
return await self._create_layout_update(model_state)
async def _parallel_render(self) -> LayoutUpdateMessage:
"""Await to fetch the first completed render within our asyncio task group.
We use the `asyncio.tasks.wait` API in order to return the first completed task.
"""
await self._render_tasks_ready.acquire()
done, _ = await wait(self._render_tasks, return_when=FIRST_COMPLETED)
update_task: Task[LayoutUpdateMessage] = done.pop()
self._render_tasks.remove(update_task)
return update_task.result()
async def _create_layout_update(
self, old_state: _ModelState
) -> LayoutUpdateMessage:
new_state = _copy_component_model_state(old_state)
component = new_state.life_cycle_state.component
async with AsyncExitStack() as exit_stack:
await self._render_component(exit_stack, old_state, new_state, component)
if REACTPY_CHECK_VDOM_SPEC.current:
validate_vdom_json(new_state.model.current)
return {
"type": "layout-update",
"path": new_state.patch_path,
"model": new_state.model.current,
}
async def _render_component(
self,
exit_stack: AsyncExitStack,
old_state: _ModelState | None,
new_state: _ModelState,
component: ComponentType,
) -> None:
life_cycle_state = new_state.life_cycle_state
life_cycle_hook = life_cycle_state.hook
self._model_states_by_life_cycle_state_id[life_cycle_state.id] = new_state
await life_cycle_hook.affect_component_will_render(component)
exit_stack.push_async_callback(life_cycle_hook.affect_layout_did_render)
try:
raw_model = component.render()
# wrap the model in a fragment (i.e. tagName="") to ensure components have
# a separate node in the model state tree. This could be removed if this
# components are given a node in the tree some other way
wrapper_model: VdomDict = {"tagName": "", "children": [raw_model]}
await self._render_model(exit_stack, old_state, new_state, wrapper_model)
except Exception as error:
logger.exception(f"Failed to render {component}")
new_state.model.current = {
"tagName": "",
"error": (
f"{type(error).__name__}: {error}"
if REACTPY_DEBUG_MODE.current
else ""
),
}
finally:
await life_cycle_hook.affect_component_did_render()
try:
parent = new_state.parent
except AttributeError:
pass # only happens for root component
else:
key, index = new_state.key, new_state.index
parent.children_by_key[key] = new_state
# need to add this model to parent's children without mutating parent model
old_parent_model = parent.model.current
old_parent_children = old_parent_model["children"]
parent.model.current = {
**old_parent_model,
"children": [
*old_parent_children[:index],
new_state.model.current,
*old_parent_children[index + 1 :],
],
}
async def _render_model(
self,
exit_stack: AsyncExitStack,
old_state: _ModelState | None,
new_state: _ModelState,
raw_model: Any,
) -> None:
try:
new_state.model.current = {"tagName": raw_model["tagName"]}
except Exception as e: # nocov
msg = f"Expected a VDOM element dict, not {raw_model}"
raise ValueError(msg) from e
if "key" in raw_model:
new_state.key = new_state.model.current["key"] = raw_model["key"]
if "importSource" in raw_model:
new_state.model.current["importSource"] = raw_model["importSource"]
self._render_model_attributes(old_state, new_state, raw_model)
await self._render_model_children(
exit_stack, old_state, new_state, raw_model.get("children", [])
)
def _render_model_attributes(
self,
old_state: _ModelState | None,
new_state: _ModelState,
raw_model: dict[str, Any],
) -> None:
# extract event handlers from 'eventHandlers' and 'attributes'
handlers_by_event: EventHandlerDict = raw_model.get("eventHandlers", {})
if "attributes" in raw_model:
attrs = raw_model["attributes"].copy()
new_state.model.current["attributes"] = attrs
if old_state is None:
self._render_model_event_handlers_without_old_state(
new_state, handlers_by_event
)
return None
for old_event in set(old_state.targets_by_event).difference(handlers_by_event):
old_target = old_state.targets_by_event[old_event]
del self._event_handlers[old_target]
if not handlers_by_event:
return None
model_event_handlers = new_state.model.current["eventHandlers"] = {}
for event, handler in handlers_by_event.items():
if event in old_state.targets_by_event:
target = old_state.targets_by_event[event]
else:
target = uuid4().hex if handler.target is None else handler.target
new_state.targets_by_event[event] = target
self._event_handlers[target] = handler
model_event_handlers[event] = {
"target": target,
"preventDefault": handler.prevent_default,
"stopPropagation": handler.stop_propagation,
}
return None
def _render_model_event_handlers_without_old_state(
self,
new_state: _ModelState,
handlers_by_event: EventHandlerDict,
) -> None:
if not handlers_by_event:
return None
model_event_handlers = new_state.model.current["eventHandlers"] = {}
for event, handler in handlers_by_event.items():
target = uuid4().hex if handler.target is None else handler.target
new_state.targets_by_event[event] = target
self._event_handlers[target] = handler
model_event_handlers[event] = {
"target": target,
"preventDefault": handler.prevent_default,
"stopPropagation": handler.stop_propagation,
}
return None
async def _render_model_children(
self,
exit_stack: AsyncExitStack,
old_state: _ModelState | None,
new_state: _ModelState,
raw_children: Any,
) -> None:
if not isinstance(raw_children, (list, tuple)):
raw_children = [raw_children]
if old_state is None:
if raw_children:
await self._render_model_children_without_old_state(
exit_stack, new_state, raw_children
)
return None
elif not raw_children:
await self._unmount_model_states(list(old_state.children_by_key.values()))
return None
children_info = _get_children_info(raw_children)
new_keys = {k for _, _, k in children_info}
if len(new_keys) != len(children_info):
key_counter = Counter(item[2] for item in children_info)
duplicate_keys = [key for key, count in key_counter.items() if count > 1]
msg = f"Duplicate keys {duplicate_keys} at {new_state.patch_path or '/'!r}"
raise ValueError(msg)
old_keys = set(old_state.children_by_key).difference(new_keys)
if old_keys:
await self._unmount_model_states(
[old_state.children_by_key[key] for key in old_keys]
)
new_state.model.current["children"] = []
for index, (child, child_type, key) in enumerate(children_info):
old_child_state = old_state.children_by_key.get(key)
if child_type is _DICT_TYPE:
old_child_state = old_state.children_by_key.get(key)
if old_child_state is None:
new_child_state = _make_element_model_state(
new_state,
index,
key,
)
elif old_child_state.is_component_state:
await self._unmount_model_states([old_child_state])
new_child_state = _make_element_model_state(
new_state,
index,
key,
)
old_child_state = None
else:
new_child_state = _update_element_model_state(
old_child_state,
new_state,
index,
)
await self._render_model(
exit_stack, old_child_state, new_child_state, child
)
new_state.append_child(new_child_state.model.current)
new_state.children_by_key[key] = new_child_state
elif child_type is _COMPONENT_TYPE:
child = cast(ComponentType, child)
old_child_state = old_state.children_by_key.get(key)
if old_child_state is None:
new_child_state = _make_component_model_state(
new_state,
index,
key,
child,
self._schedule_render_task,
)
elif old_child_state.is_component_state and (
old_child_state.life_cycle_state.component.type != child.type
):
await self._unmount_model_states([old_child_state])
old_child_state = None
new_child_state = _make_component_model_state(
new_state,
index,
key,
child,
self._schedule_render_task,
)
else:
new_child_state = _update_component_model_state(
old_child_state,
new_state,
index,
child,
self._schedule_render_task,
)
await self._render_component(
exit_stack, old_child_state, new_child_state, child
)
else:
old_child_state = old_state.children_by_key.get(key)
if old_child_state is not None:
await self._unmount_model_states([old_child_state])
new_state.append_child(child)
async def _render_model_children_without_old_state(
self,
exit_stack: AsyncExitStack,
new_state: _ModelState,
raw_children: list[Any],
) -> None:
children_info = _get_children_info(raw_children)
new_keys = {k for _, _, k in children_info}
if len(new_keys) != len(children_info):
key_counter = Counter(k for _, _, k in children_info)
duplicate_keys = [key for key, count in key_counter.items() if count > 1]
msg = f"Duplicate keys {duplicate_keys} at {new_state.patch_path or '/'!r}"
raise ValueError(msg)
new_state.model.current["children"] = []
for index, (child, child_type, key) in enumerate(children_info):
if child_type is _DICT_TYPE:
child_state = _make_element_model_state(new_state, index, key)
await self._render_model(exit_stack, None, child_state, child)
new_state.append_child(child_state.model.current)
new_state.children_by_key[key] = child_state
elif child_type is _COMPONENT_TYPE:
child_state = _make_component_model_state(
new_state, index, key, child, self._schedule_render_task
)
await self._render_component(exit_stack, None, child_state, child)
else:
new_state.append_child(child)
async def _unmount_model_states(self, old_states: list[_ModelState]) -> None:
to_unmount = old_states[::-1] # unmount in reversed order of rendering
while to_unmount:
model_state = to_unmount.pop()
for target in model_state.targets_by_event.values():
del self._event_handlers[target]
if model_state.is_component_state:
life_cycle_state = model_state.life_cycle_state
del self._model_states_by_life_cycle_state_id[life_cycle_state.id]
await life_cycle_state.hook.affect_component_will_unmount()
to_unmount.extend(model_state.children_by_key.values())
def _schedule_render_task(self, lcs_id: _LifeCycleStateId) -> None:
if not REACTPY_ASYNC_RENDERING.current:
self._rendering_queue.put(lcs_id)
return None
try:
model_state = self._model_states_by_life_cycle_state_id[lcs_id]
except KeyError:
logger.debug(
"Did not render component with model state ID "
f"{lcs_id!r} - component already unmounted"
)
else:
self._render_tasks.add(create_task(self._create_layout_update(model_state)))
self._render_tasks_ready.release()
def __repr__(self) -> str:
return f"{type(self).__name__}({self.root})"
def _new_root_model_state(
component: ComponentType, schedule_render: Callable[[_LifeCycleStateId], None]
) -> _ModelState:
return _ModelState(
parent=None,
index=-1,
key=None,
model=Ref(),
patch_path="",
children_by_key={},
targets_by_event={},
life_cycle_state=_make_life_cycle_state(component, schedule_render),
)
def _make_component_model_state(
parent: _ModelState,
index: int,
key: Any,
component: ComponentType,
schedule_render: Callable[[_LifeCycleStateId], None],
) -> _ModelState:
return _ModelState(
parent=parent,
index=index,
key=key,
model=Ref(),
patch_path=f"{parent.patch_path}/children/{index}",
children_by_key={},
targets_by_event={},
life_cycle_state=_make_life_cycle_state(component, schedule_render),
)
def _copy_component_model_state(old_model_state: _ModelState) -> _ModelState:
# use try/except here because not having a parent is rare (only the root state)
try:
parent: _ModelState | None = old_model_state.parent
except AttributeError:
parent = None
return _ModelState(
parent=parent,
index=old_model_state.index,
key=old_model_state.key,
model=Ref(), # does not copy the model
patch_path=old_model_state.patch_path,
children_by_key={},
targets_by_event={},
life_cycle_state=old_model_state.life_cycle_state,
)
def _update_component_model_state(
old_model_state: _ModelState,
new_parent: _ModelState,
new_index: int,
new_component: ComponentType,
schedule_render: Callable[[_LifeCycleStateId], None],
) -> _ModelState:
return _ModelState(
parent=new_parent,
index=new_index,
key=old_model_state.key,
model=Ref(), # does not copy the model
patch_path=f"{new_parent.patch_path}/children/{new_index}",
children_by_key={},
targets_by_event={},
life_cycle_state=(
_update_life_cycle_state(old_model_state.life_cycle_state, new_component)
if old_model_state.is_component_state
else _make_life_cycle_state(new_component, schedule_render)
),
)
def _make_element_model_state(
parent: _ModelState,
index: int,
key: Any,
) -> _ModelState:
return _ModelState(
parent=parent,
index=index,
key=key,
model=Ref(),
patch_path=f"{parent.patch_path}/children/{index}",
children_by_key={},
targets_by_event={},
)
def _update_element_model_state(
old_model_state: _ModelState,
new_parent: _ModelState,
new_index: int,
) -> _ModelState:
return _ModelState(
parent=new_parent,
index=new_index,
key=old_model_state.key,
model=Ref(), # does not copy the model
patch_path=old_model_state.patch_path,
children_by_key={},
targets_by_event={},
)
class _ModelState:
"""State that is bound to a particular element within the layout"""
__slots__ = (
"__weakref__",
"_parent_ref",
"_render_semaphore",
"children_by_key",
"index",
"key",
"life_cycle_state",
"model",
"patch_path",
"targets_by_event",
)
def __init__(
self,
parent: _ModelState | None,
index: int,
key: Any,
model: Ref[VdomJson],
patch_path: str,
children_by_key: dict[Key, _ModelState],
targets_by_event: dict[str, str],
life_cycle_state: _LifeCycleState | None = None,
):
self.index = index
"""The index of the element amongst its siblings"""
self.key = key
"""A key that uniquely identifies the element amongst its siblings"""
self.model = model
"""The actual model of the element"""
self.patch_path = patch_path
"""A "/" delimited path to the element within the greater layout"""
self.children_by_key = children_by_key
"""Child model states indexed by their unique keys"""
self.targets_by_event = targets_by_event
"""The element's event handler target strings indexed by their event name"""
# === Conditionally Available Attributes ===
# It's easier to conditionally assign than to force a null check on every usage
if parent is not None:
self._parent_ref = weakref(parent)
"""The parent model state"""
if life_cycle_state is not None:
self.life_cycle_state = life_cycle_state
"""The state for the element's component (if it has one)"""
@property
def is_component_state(self) -> bool:
return hasattr(self, "life_cycle_state")
@property
def parent(self) -> _ModelState:
parent = self._parent_ref()
if parent is None:
raise RuntimeError("detached model state") # nocov
return parent
def append_child(self, child: Any) -> None:
self.model.current["children"].append(child)
def __repr__(self) -> str: # nocov
return f"ModelState({ {s: getattr(self, s, None) for s in self.__slots__} })"
def _make_life_cycle_state(
component: ComponentType,
schedule_render: Callable[[_LifeCycleStateId], None],
) -> _LifeCycleState:
life_cycle_state_id = _LifeCycleStateId(uuid4().hex)
return _LifeCycleState(
life_cycle_state_id,
LifeCycleHook(lambda: schedule_render(life_cycle_state_id)),
component,
)
def _update_life_cycle_state(
old_life_cycle_state: _LifeCycleState,
new_component: ComponentType,
) -> _LifeCycleState:
return _LifeCycleState(
old_life_cycle_state.id,
# the hook is preserved across renders because it holds the state
old_life_cycle_state.hook,
new_component,
)
_LifeCycleStateId = NewType("_LifeCycleStateId", str)
class _LifeCycleState(NamedTuple):
"""Component state for :class:`_ModelState`"""
id: _LifeCycleStateId
"""A unique identifier used in the :class:`~reactpy.core.hooks.LifeCycleHook` callback"""
hook: LifeCycleHook
"""The life cycle hook"""
component: ComponentType
"""The current component instance"""
_Type = TypeVar("_Type")
class _ThreadSafeQueue(Generic[_Type]):
def __init__(self) -> None:
self._loop = get_running_loop()
self._queue: Queue[_Type] = Queue()
self._pending: set[_Type] = set()
def put(self, value: _Type) -> None:
if value not in self._pending:
self._pending.add(value)
self._loop.call_soon_threadsafe(self._queue.put_nowait, value)
async def get(self) -> _Type:
value = await self._queue.get()
self._pending.remove(value)
return value
def _get_children_info(children: list[VdomChild]) -> Sequence[_ChildInfo]:
infos: list[_ChildInfo] = []
for index, child in enumerate(children):
if child is None:
continue
elif isinstance(child, dict):
child_type = _DICT_TYPE
key = child.get("key")
elif isinstance(child, ComponentType):
child_type = _COMPONENT_TYPE
key = child.key
else:
child = f"{child}"
child_type = _STRING_TYPE
key = None
if key is None:
key = index
infos.append((child, child_type, key))
return infos
_ChildInfo: TypeAlias = tuple[Any, "_ElementType", Key]
# used in _process_child_type_and_key
_ElementType = NewType("_ElementType", int)
_DICT_TYPE = _ElementType(1)
_COMPONENT_TYPE = _ElementType(2)
_STRING_TYPE = _ElementType(3)