Add a serialize middleware step to keep from having to check if the request exists in all build middleware

Author: jeskew

packages/middleware-content-length/src/index.ts

@@ -14,11 +14,7 @@ export function contentLengthMiddleware(
     ): BuildHandler<any, Output, any> => async (
         args: BuildHandlerArguments<any, any>
     ): Promise<Output> => {
-        const {request} = args;
-        if (!request) {
-            throw new Error('Unable to determine request content-length due to missing request.');
-        }
-
+        let request = {...args.request};
         const {body, headers} = request;
         if (
             body &&
@@ -28,7 +24,10 @@ export function contentLengthMiddleware(
         ) {
             const length = bodyLengthCalculator(body);
             if (length !== undefined) {
-                headers['Content-Length'] = String(length);
+                request.headers = {
+                    ...request.headers,
+                    'Content-Length': String(length),
+                }
             }
         }
 

packages/middleware-stack/src/index.ts

@@ -5,10 +5,9 @@ import {
     Middleware,
     MiddlewareStack as IMiddlewareStack,
     HandlerExecutionContext,
+    Step,
 } from '@aws/types';
 
-export type Step = 'initialize'|'build'|'finalize';
-
 interface HandlerListEntry<
     Input extends object,
     Output extends object,
@@ -20,11 +19,17 @@ interface HandlerListEntry<
     tags?: {[tag: string]: any};
 }
 
+export interface MiddlewareStack<
+    Input extends object,
+    Output extends object,
+    Stream = Uint8Array
+> extends IMiddlewareStack<Input, Output, Stream> {}
+
 export class MiddlewareStack<
     Input extends object,
     Output extends object,
     Stream = Uint8Array
-> implements IMiddlewareStack<Input, Output, Stream> {
+> {
     private readonly entries: Array<HandlerListEntry<Input, Output, Stream>> = [];
     private sorted: boolean = true;
 
@@ -117,7 +122,8 @@ export class MiddlewareStack<
 }
 
 const stepWeights = {
-    initialize: 3,
+    initialize: 4,
+    serialize: 3,
     build: 2,
     finalize: 1,
 };