reflex/reflex/middleware/hydrate_middleware.py
Masen Furer a2243190ff
[ENG-4326] Async ComputedVar (#4711)
* WiP

* Save the var from get_var_name

* flatten StateManagerRedis.get_state algorithm

simplify fetching of states and avoid repeatedly fetching the same state

* Get all the states in a single redis round-trip

* update docstrings in StateManagerRedis

* Move computed var dep tracking to separate module

* Fix pre-commit issues

* ComputedVar.add_dependency: explicitly dependency declaration

Allow var dependencies to be added at runtime, for example, when defining a
ComponentState that depends on vars that cannot be known statically.

Fix more pyright issues.

* Fix/ignore more pyright issues from recent merge

* handle cleaning out _potentially_dirty_states on reload

* ignore accessed attributes missing on state class

these might be added dynamically later in which case we recompute the
dependency tracking dicts... if not, they'll blow up anyway at runtime.

* fix playwright tests, which insist on running an asyncio loop

---------

Co-authored-by: Khaleel Al-Adhami <khaleel.aladhami@gmail.com>
2025-01-31 16:33:30 -08:00

51 lines
1.5 KiB
Python

"""Middleware to hydrate the state."""
from __future__ import annotations
import dataclasses
from typing import TYPE_CHECKING, Optional
from reflex import constants
from reflex.event import Event, get_hydrate_event
from reflex.middleware.middleware import Middleware
from reflex.state import BaseState, StateUpdate, _resolve_delta
if TYPE_CHECKING:
from reflex.app import App
@dataclasses.dataclass(init=True)
class HydrateMiddleware(Middleware):
"""Middleware to handle initial app hydration."""
async def preprocess(
self, app: App, state: BaseState, event: Event
) -> Optional[StateUpdate]:
"""Preprocess the event.
Args:
app: The app to apply the middleware to.
state: The client state.
event: The event to preprocess.
Returns:
An optional delta or list of state updates to return.
"""
# If this is not the hydrate event, return None
if event.name != get_hydrate_event(state):
return None
# Clear client storage, to respect clearing cookies
state._reset_client_storage()
# Mark state as not hydrated (until on_loads are complete)
setattr(state, constants.CompileVars.IS_HYDRATED, False)
# Get the initial state.
delta = await _resolve_delta(state.dict())
# since a full dict was captured, clean any dirtiness
state._clean()
# Return the state update.
return StateUpdate(delta=delta, events=[])