Fix UIAdapter.dispatch_request typing (#3721)

Author: dmontagu

pydantic_ai_slim/pydantic_ai/ui/_adapter.py

@@ -13,6 +13,7 @@
     Generic,
     Protocol,
     TypeVar,
+    cast,
     runtime_checkable,
 )
 
@@ -43,7 +44,6 @@
     'StateDeps',
 ]
 
-
 RunInputT = TypeVar('RunInputT')
 """Type variable for protocol-specific run input types."""
 
@@ -53,10 +53,12 @@
 EventT = TypeVar('EventT')
 """Type variable for protocol-specific event types."""
 
-
 StateT = TypeVar('StateT', bound=BaseModel)
 """Type variable for the state type, which must be a subclass of `BaseModel`."""
 
+DispatchDepsT = TypeVar('DispatchDepsT')
+"""TypeVar for deps to avoid awkwardness with unbound classvar deps."""
+
 
 @runtime_checkable
 class StateHandler(Protocol):
@@ -328,18 +330,18 @@ async def dispatch_request(
         cls,
         request: Request,
         *,
-        agent: AbstractAgent[AgentDepsT, OutputDataT],
+        agent: AbstractAgent[DispatchDepsT, OutputDataT],
         message_history: Sequence[ModelMessage] | None = None,
         deferred_tool_results: DeferredToolResults | None = None,
         model: Model | KnownModelName | str | None = None,
-        instructions: Instructions[AgentDepsT] = None,
-        deps: AgentDepsT = None,
+        instructions: Instructions[DispatchDepsT] = None,
+        deps: DispatchDepsT = None,
         output_type: OutputSpec[Any] | None = None,
         model_settings: ModelSettings | None = None,
         usage_limits: UsageLimits | None = None,
         usage: RunUsage | None = None,
         infer_name: bool = True,
-        toolsets: Sequence[AbstractToolset[AgentDepsT]] | None = None,
+        toolsets: Sequence[AbstractToolset[DispatchDepsT]] | None = None,
         builtin_tools: Sequence[AbstractBuiltinTool] | None = None,
         on_complete: OnCompleteFunc[EventT] | None = None,
     ) -> Response:
@@ -376,7 +378,11 @@ async def dispatch_request(
             ) from e
 
         try:
-            adapter = await cls.from_request(request, agent=agent)
+            # The DepsT comes from `agent`, not from `cls`; the cast is necessary to explain this to pyright
+            adapter = cast(
+                UIAdapter[RunInputT, MessageT, EventT, DispatchDepsT, OutputDataT],
+                await cls.from_request(request, agent=agent),
+            )
         except ValidationError as e:  # pragma: no cover
             return Response(
                 content=e.json(),