v1: Fix use_effect hook with async handler (#5762)

* Replace Exception with specific error types

Replaces generic Exception raises with more specific error types such as RuntimeError, ValueError, NotImplementedError, ImportError, and custom exceptions across multiple modules. This improves error handling clarity and aligns with Python best practices for exception usage.

* Set res to None before running hook setup

Added initialization of the 'res' variable to None before executing hook setup in the Session class. This change clarifies the state of 'res' prior to its use and may help prevent potential issues with uninitialized variables.

* Improve upload size exceeded error message

The HTTP 413 error now includes the maximum allowed upload size in bytes for better clarity when the limit is exceeded.

Author: FeodorFitsner

sdk/python/packages/flet-web/src/flet_web/fastapi/flet_upload.py

@@ -112,6 +112,7 @@ async def handle(self, request: Request):
                 if self.__max_upload_size and size > self.__max_upload_size:
                     raise HTTPException(
                         status_code=status.HTTP_413_REQUEST_ENTITY_TOO_LARGE,
-                        detail="Max upload size exceeded",
+                        detail="Max upload size exceeded: "
+                        f"{self.__max_upload_size} bytes",
                     )
                 await f.write(chunk)

sdk/python/packages/flet/src/flet/messaging/session.py

@@ -346,6 +346,7 @@ async def __updates_scheduler(self):
                     # print(f"**** Running effect: {hook} {is_cleanup}")
                     if hook and hook.setup and not is_cleanup:
                         hook.cancel()
+                        res = None
                         if asyncio.iscoroutinefunction(hook.setup):
                             hook._setup_task = asyncio.create_task(hook.setup())
                         else: