fix(types): use SerdeFunctions type as serde plugin input, but call s…

…erde functions as type SerdeContext (#1183)

* fix(types): use optional endpoint for inputs to serializer middleware

* docs: add comments describing cast of SerdeFunctions to CommandSerdeContext

* fix: add default types (any) for serde plugin

* docs: remove code comments that no longer apply

.changeset/many-stingrays-bow.md

@@ -0,0 +1,5 @@
+---
+"@smithy/middleware-serde": patch
+---
+
+use SerdeFunctions as input type and SerdeContext as resolved type for serde plugin

packages/middleware-serde/src/deserializerMiddleware.ts

@@ -5,17 +5,20 @@ import {
   DeserializeMiddleware,
   HandlerExecutionContext,
   ResponseDeserializer,
+  SerdeContext,
   SerdeFunctions,
 } from "@smithy/types";
 
 /**
  * @internal
- *
- * 3rd type parameter is deprecated and unused.
  */
-export const deserializerMiddleware = <Input extends object, Output extends object, _ = any>(
+export const deserializerMiddleware = <
+  Input extends object = any,
+  Output extends object = any,
+  CommandSerdeContext extends SerdeContext = any
+>(
   options: SerdeFunctions,
-  deserializer: ResponseDeserializer<any, any, SerdeFunctions>
+  deserializer: ResponseDeserializer<any, any, CommandSerdeContext>
 ): DeserializeMiddleware<Input, Output> => (
   next: DeserializeHandler<Input, Output>,
   context: HandlerExecutionContext
@@ -24,7 +27,14 @@ export const deserializerMiddleware = <Input extends object, Output extends obje
 ): Promise<DeserializeHandlerOutput<Output>> => {
   const { response } = await next(args);
   try {
-    const parsed = await deserializer(response, options);
+    /**
+     * [options] is upgraded from SerdeFunctions to CommandSerdeContext,
+     * since the generated deserializer expects CommandSerdeContext.
+     *
+     * This is okay because options is from the same client's resolved config,
+     * and the deserializer doesn't need the `endpoint` field.
+     */
+    const parsed = await deserializer(response, options as CommandSerdeContext);
     return {
       response,
       output: parsed as Output,

packages/middleware-serde/src/serdePlugin.ts

@@ -1,13 +1,13 @@
 import {
   DeserializeHandlerOptions,
   Endpoint,
-  EndpointBearer,
   MetadataBearer,
   MiddlewareStack,
   Pluggable,
   Provider,
   RequestSerializer,
   ResponseDeserializer,
+  SerdeContext,
   SerdeFunctions,
   SerializeHandlerOptions,
   UrlParser,
@@ -43,12 +43,15 @@ export type V1OrV2Endpoint = {
 /**
  * @internal
  *
- * Note: 2nd type parameter is deprecated and unused.
  */
-export function getSerdePlugin<InputType extends object, _, OutputType extends MetadataBearer>(
+export function getSerdePlugin<
+  InputType extends object = any,
+  CommandSerdeContext extends SerdeContext = any,
+  OutputType extends MetadataBearer = any
+>(
   config: V1OrV2Endpoint & SerdeFunctions,
-  serializer: RequestSerializer<any, SerdeFunctions & EndpointBearer>,
-  deserializer: ResponseDeserializer<OutputType, any, SerdeFunctions>
+  serializer: RequestSerializer<any, CommandSerdeContext>,
+  deserializer: ResponseDeserializer<OutputType, any, CommandSerdeContext>
 ): Pluggable<InputType, OutputType> {
   return {
     applyToStack: (commandStack: MiddlewareStack<InputType, OutputType>) => {

packages/middleware-serde/src/serializerMiddleware.ts

@@ -1,7 +1,9 @@
 import {
-  EndpointBearer,
+  Endpoint,
   HandlerExecutionContext,
+  Provider,
   RequestSerializer,
+  SerdeContext,
   SerdeFunctions,
   SerializeHandler,
   SerializeHandlerArguments,
@@ -13,19 +15,21 @@ import type { V1OrV2Endpoint } from "./serdePlugin";
 
 /**
  * @internal
- *
- * Note: 3rd type parameter is deprecated and unused.
  */
-export const serializerMiddleware = <Input extends object, Output extends object, _>(
+export const serializerMiddleware = <
+  Input extends object = any,
+  Output extends object = any,
+  CommandSerdeContext extends SerdeContext = any
+>(
   options: V1OrV2Endpoint & SerdeFunctions,
-  serializer: RequestSerializer<any, SerdeFunctions & EndpointBearer>
+  serializer: RequestSerializer<any, CommandSerdeContext>
 ): SerializeMiddleware<Input, Output> => (
   next: SerializeHandler<Input, Output>,
   context: HandlerExecutionContext
 ): SerializeHandler<Input, Output> => async (
   args: SerializeHandlerArguments<Input>
 ): Promise<SerializeHandlerOutput<Output>> => {
-  const endpoint =
+  const endpoint: Provider<Endpoint> =
     context.endpointV2?.url && options.urlParser
       ? async () => options.urlParser!(context.endpointV2!.url as URL)
       : options.endpoint!;
@@ -34,7 +38,14 @@ export const serializerMiddleware = <Input extends object, Output extends object
     throw new Error("No valid endpoint provider available.");
   }
 
-  const request = await serializer(args.input, { ...options, endpoint });
+  /**
+   * [options] is upgraded from SerdeFunctions to CommandSerdeContext,
+   * since the generated serializer expects CommandSerdeContext.
+   *
+   * This is okay because options is from the same client's resolved config,
+   * and `endpoint` has been provided here by checking two sources.
+   */
+  const request = await serializer(args.input, { ...options, endpoint } as CommandSerdeContext);
 
   return next({
     ...args,