use better typing for on_load (#4274)

* use better typing for on_load

* make app dataclass

* get it right pyright

* make lifespan into a dataclass

reflex/app.py

@@ -46,7 +46,6 @@ from starlette_admin.contrib.sqla.view import ModelView
 from reflex import constants
 from reflex.admin import AdminDash
 from reflex.app_mixins import AppMixin, LifespanMixin, MiddlewareMixin
-from reflex.base import Base
 from reflex.compiler import compiler
 from reflex.compiler import utils as compiler_utils
 from reflex.compiler.compiler import (
@@ -70,7 +69,14 @@ from reflex.components.core.client_side_routing import (
 from reflex.components.core.upload import Upload, get_upload_dir
 from reflex.components.radix import themes
 from reflex.config import environment, get_config
-from reflex.event import Event, EventHandler, EventSpec, window_alert
+from reflex.event import (
+    Event,
+    EventHandler,
+    EventSpec,
+    EventType,
+    IndividualEventType,
+    window_alert,
+)
 from reflex.model import Model, get_db_status
 from reflex.page import (
     DECORATED_PAGES,
@@ -189,11 +195,12 @@ class UnevaluatedPage:
     title: Union[Var, str, None]
     description: Union[Var, str, None]
     image: str
-    on_load: Union[EventHandler, EventSpec, List[Union[EventHandler, EventSpec]], None]
+    on_load: Union[EventType[[]], None]
     meta: List[Dict[str, str]]
 
 
-class App(MiddlewareMixin, LifespanMixin, Base):
+@dataclasses.dataclass()
+class App(MiddlewareMixin, LifespanMixin):
     """The main Reflex app that encapsulates the backend and frontend.
 
     Every Reflex app needs an app defined in its main module.
@@ -215,24 +222,26 @@ class App(MiddlewareMixin, LifespanMixin, Base):
     """
 
     # The global [theme](https://reflex.dev/docs/styling/theming/#theme) for the entire app.
-    theme: Optional[Component] = themes.theme(accent_color="blue")
+    theme: Optional[Component] = dataclasses.field(
+        default_factory=lambda: themes.theme(accent_color="blue")
+    )
 
     # The [global style](https://reflex.dev/docs/styling/overview/#global-styles}) for the app.
-    style: ComponentStyle = {}
+    style: ComponentStyle = dataclasses.field(default_factory=dict)
 
     # A list of URLs to [stylesheets](https://reflex.dev/docs/styling/custom-stylesheets/) to include in the app.
-    stylesheets: List[str] = []
+    stylesheets: List[str] = dataclasses.field(default_factory=list)
 
     # A component that is present on every page (defaults to the Connection Error banner).
     overlay_component: Optional[Union[Component, ComponentCallable]] = (
-        default_overlay_component()
+        dataclasses.field(default_factory=default_overlay_component)
     )
 
     # Error boundary component to wrap the app with.
     error_boundary: Optional[ComponentCallable] = default_error_boundary
 
     # Components to add to the head of every page.
-    head_components: List[Component] = []
+    head_components: List[Component] = dataclasses.field(default_factory=list)
 
     # The Socket.IO AsyncServer instance.
     sio: Optional[AsyncServer] = None
@@ -244,10 +253,12 @@ class App(MiddlewareMixin, LifespanMixin, Base):
     html_custom_attrs: Optional[Dict[str, str]] = None
 
     # A map from a route to an unevaluated page. PRIVATE.
-    unevaluated_pages: Dict[str, UnevaluatedPage] = {}
+    unevaluated_pages: Dict[str, UnevaluatedPage] = dataclasses.field(
+        default_factory=dict
+    )
 
     # A map from a page route to the component to render. Users should use `add_page`. PRIVATE.
-    pages: Dict[str, Component] = {}
+    pages: Dict[str, Component] = dataclasses.field(default_factory=dict)
 
     # The backend API object. PRIVATE.
     api: FastAPI = None  # type: ignore
@@ -259,7 +270,9 @@ class App(MiddlewareMixin, LifespanMixin, Base):
     _state_manager: Optional[StateManager] = None
 
     # Mapping from a route to event handlers to trigger when the page loads. PRIVATE.
-    load_events: Dict[str, List[Union[EventHandler, EventSpec]]] = {}
+    load_events: Dict[str, List[IndividualEventType[[]]]] = dataclasses.field(
+        default_factory=dict
+    )
 
     # Admin dashboard to view and manage the database. PRIVATE.
     admin_dash: Optional[AdminDash] = None
@@ -268,7 +281,7 @@ class App(MiddlewareMixin, LifespanMixin, Base):
     event_namespace: Optional[EventNamespace] = None
 
     # Background tasks that are currently running. PRIVATE.
-    background_tasks: Set[asyncio.Task] = set()
+    background_tasks: Set[asyncio.Task] = dataclasses.field(default_factory=set)
 
     # Frontend Error Handler Function
     frontend_exception_handler: Callable[[Exception], None] = (
@@ -280,23 +293,14 @@ class App(MiddlewareMixin, LifespanMixin, Base):
         [Exception], Union[EventSpec, List[EventSpec], None]
     ] = default_backend_exception_handler
 
-    def __init__(self, **kwargs):
+    def __post_init__(self):
         """Initialize the app.
 
-        Args:
-            **kwargs: Kwargs to initialize the app with.
-
         Raises:
             ValueError: If the event namespace is not provided in the config.
                         Also, if there are multiple client subclasses of rx.BaseState(Subclasses of rx.BaseState should consist
                         of the DefaultState and the client app state).
         """
-        if "connect_error_component" in kwargs:
-            raise ValueError(
-                "`connect_error_component` is deprecated, use `overlay_component` instead"
-            )
-        super().__init__(**kwargs)
-
         # Special case to allow test cases have multiple subclasses of rx.BaseState.
         if not is_testing_env() and BaseState.__subclasses__() != [State]:
             # Only rx.State is allowed as Base State subclass.
@@ -471,9 +475,7 @@ class App(MiddlewareMixin, LifespanMixin, Base):
         title: str | Var | None = None,
         description: str | Var | None = None,
         image: str = constants.DefaultPage.IMAGE,
-        on_load: (
-            EventHandler | EventSpec | list[EventHandler | EventSpec] | None
-        ) = None,
+        on_load: EventType[[]] | None = None,
         meta: list[dict[str, str]] = constants.DefaultPage.META_LIST,
     ):
         """Add a page to the app.
@@ -559,7 +561,7 @@ class App(MiddlewareMixin, LifespanMixin, Base):
         self._check_routes_conflict(route)
         self.pages[route] = component
 
-    def get_load_events(self, route: str) -> list[EventHandler | EventSpec]:
+    def get_load_events(self, route: str) -> list[IndividualEventType[[]]]:
         """Get the load events for a route.
 
         Args:
@@ -618,9 +620,7 @@ class App(MiddlewareMixin, LifespanMixin, Base):
         title: str = constants.Page404.TITLE,
         image: str = constants.Page404.IMAGE,
         description: str = constants.Page404.DESCRIPTION,
-        on_load: (
-            EventHandler | EventSpec | list[EventHandler | EventSpec] | None
-        ) = None,
+        on_load: EventType[[]] | None = None,
         meta: list[dict[str, str]] = constants.DefaultPage.META_LIST,
     ):
         """Define a custom 404 page for any url having no match.

reflex/app_mixins/lifespan.py

@@ -4,6 +4,7 @@ from __future__ import annotations
 
 import asyncio
 import contextlib
+import dataclasses
 import functools
 import inspect
 from typing import Callable, Coroutine, Set, Union
@@ -16,11 +17,14 @@ from reflex.utils.exceptions import InvalidLifespanTaskType
 from .mixin import AppMixin
 
 
+@dataclasses.dataclass
 class LifespanMixin(AppMixin):
     """A Mixin that allow tasks to run during the whole app lifespan."""
 
     # Lifespan tasks that are planned to run.
-    lifespan_tasks: Set[Union[asyncio.Task, Callable]] = set()
+    lifespan_tasks: Set[Union[asyncio.Task, Callable]] = dataclasses.field(
+        default_factory=set
+    )
 
     @contextlib.asynccontextmanager
     async def _run_lifespan_tasks(self, app: FastAPI):

reflex/app_mixins/middleware.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import asyncio
+import dataclasses
 from typing import List
 
 from reflex.event import Event
@@ -12,11 +13,12 @@ from reflex.state import BaseState, StateUpdate
 from .mixin import AppMixin
 
 
+@dataclasses.dataclass
 class MiddlewareMixin(AppMixin):
     """Middleware Mixin that allow to add middleware to the app."""
 
     # Middleware to add to the app. Users should use `add_middleware`. PRIVATE.
-    middleware: List[Middleware] = []
+    middleware: List[Middleware] = dataclasses.field(default_factory=list)
 
     def _init_mixin(self):
         self.middleware.append(HydrateMiddleware())

reflex/app_mixins/mixin.py

@@ -1,9 +1,10 @@
 """Default mixin for all app mixins."""
 
-from reflex.base import Base
+import dataclasses
 
 
-class AppMixin(Base):
+@dataclasses.dataclass
+class AppMixin:
     """Define the base class for all app mixins."""
 
     def _init_mixin(self):

reflex/page.py

@@ -6,6 +6,7 @@ from collections import defaultdict
 from typing import Any, Dict, List
 
 from reflex.config import get_config
+from reflex.event import EventType
 
 DECORATED_PAGES: Dict[str, List] = defaultdict(list)
 
@@ -17,7 +18,7 @@ def page(
     description: str | None = None,
     meta: list[Any] | None = None,
     script_tags: list[Any] | None = None,
-    on_load: Any | list[Any] | None = None,
+    on_load: EventType[[]] | None = None,
 ):
     """Decorate a function as a page.
 

tests/units/test_app.py

@@ -1211,7 +1211,7 @@ async def test_process_events(mocker, token: str):
     ],
 )
 def test_overlay_component(
-    state: State | None,
+    state: Type[State] | None,
     overlay_component: Component | ComponentCallable | None,
     exp_page_child: Type[Component] | None,
 ):
@@ -1403,13 +1403,6 @@ def test_app_state_determination():
     assert a4.state is not None
 
 
-# for coverage
-def test_raise_on_connect_error():
-    """Test that the connect_error function is called."""
-    with pytest.raises(ValueError):
-        App(connect_error_component="Foo")
-
-
 def test_raise_on_state():
     """Test that the state is set."""
     # state kwargs is deprecated, we just make sure the app is created anyway.

tests/units/test_state.py

@@ -2725,6 +2725,7 @@ class OnLoadState(State):
 
     num: int = 0
 
+    @rx.event
     def test_handler(self):
         """Test handler."""
         self.num += 1