fix(core/protocols): drain Unit response streams in HttpBindingProtocol

.changeset/nervous-lies-film.md

@@ -0,0 +1,5 @@
+---
+"@smithy/core": patch
+---
+
+drain stream in httpBindingProtocol with unit output

packages/core/src/submodules/protocols/HttpBindingProtocol.spec.ts

@@ -1,4 +1,5 @@
 import { op } from "@smithy/core/schema";
+import { streamCollector } from "@smithy/node-http-handler";
 import { HttpResponse } from "@smithy/protocol-http";
 import type {
   $Schema,
@@ -20,6 +21,7 @@ import type {
   TimestampEpochSecondsSchema,
 } from "@smithy/types";
 import { parseUrl } from "@smithy/url-parser/src";
+import { Readable } from "node:stream";
 import { describe, expect, test as it } from "vitest";
 
 import { HttpBindingProtocol } from "./HttpBindingProtocol";
@@ -244,4 +246,42 @@ describe(HttpBindingProtocol.name, () => {
     expect(request.path).toMatch(/[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}/);
     expect(request.headers?.["header-token"]).toMatch(/^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/);
   });
+
+  it("should discard response bodies for Unit operation outputs, making no attempt to parse them", async () => {
+    const protocol = new StringRestProtocol();
+    let streamProgress = 0;
+    const response = await protocol.deserializeResponse(
+      op("", "", {}, "unit", "unit"),
+      {
+        streamCollector: streamCollector,
+      } as any,
+      new HttpResponse({
+        statusCode: 200,
+        headers: {},
+        body: Readable.from({
+          async *[Symbol.asyncIterator]() {
+            yield "@";
+            streamProgress = 25;
+            yield "#";
+            streamProgress = 50;
+            yield "$";
+            streamProgress = 75;
+            yield "%";
+            streamProgress = 100;
+          },
+        }),
+      })
+    );
+
+    expect(response).toEqual({
+      $metadata: {
+        cfId: undefined,
+        extendedRequestId: undefined,
+        httpStatusCode: 200,
+        requestId: undefined,
+      },
+    });
+
+    expect(streamProgress).toBe(100);
+  });
 });

packages/core/src/submodules/protocols/HttpBindingProtocol.ts

@@ -229,6 +229,8 @@ export abstract class HttpBindingProtocol extends HttpProtocol {
       }
       // Due to Smithy validation, we can assume that the members with no HTTP
       // bindings DO NOT contain an event stream.
+    } else if (nonHttpBindingMembers.discardResponseBody) {
+      await collectBody(response.body, context);
     }
 
     dataObject.$metadata = this.deserializeMetadata(response);
@@ -247,35 +249,37 @@ export abstract class HttpBindingProtocol extends HttpProtocol {
     response: IHttpResponse,
     headerBindings: Set<string>,
     dataObject: any
-  ): Promise<string[]>;
+  ): Promise<string[] & { discardResponseBody?: boolean }>;
   protected async deserializeHttpMessage(
     schema: Schema,
     context: HandlerExecutionContext & SerdeFunctions,
     response: IHttpResponse,
     dataObject: any
-  ): Promise<string[]>;
+  ): Promise<string[] & { discardResponseBody?: boolean }>;
   protected async deserializeHttpMessage(
     schema: Schema,
     context: HandlerExecutionContext & SerdeFunctions,
     response: IHttpResponse,
     arg4: unknown,
     arg5?: unknown
-  ): Promise<string[]> {
+  ): Promise<string[] & { discardResponseBody?: boolean }> {
     let dataObject: any;
     if (arg4 instanceof Set) {
       dataObject = arg5;
     } else {
       dataObject = arg4;
     }
 
+    let discardResponseBody = true;
     const deserializer = this.deserializer;
     const ns = NormalizedSchema.of(schema);
-    const nonHttpBindingMembers = [] as string[];
+    const nonHttpBindingMembers = [] as string[] & { discardResponseBody?: boolean };
 
     for (const [memberName, memberSchema] of ns.structIterator()) {
       const memberTraits = memberSchema.getMemberTraits();
 
       if (memberTraits.httpPayload) {
+        discardResponseBody = false;
         const isStreaming = memberSchema.isStreaming();
         if (isStreaming) {
           const isEventStream = memberSchema.isStructSchema();
@@ -339,6 +343,7 @@ export abstract class HttpBindingProtocol extends HttpProtocol {
         nonHttpBindingMembers.push(memberName);
       }
     }
+    nonHttpBindingMembers.discardResponseBody = discardResponseBody;
     return nonHttpBindingMembers;
   }
 }