[core] Allow setting content-type header even if there is no request body

sdk/core/ts-http-runtime/CHANGELOG.md

@@ -8,6 +8,8 @@
 
 ### Bugs Fixed
 
+- Fixed an issue where setting `content-type` header was ignored when the request has no body. [#37181](https://github.com/Azure/azure-sdk-for-js/pull/37181)
+
 ### Other Changes
 
 ## 0.3.2 (2025-11-06)

sdk/core/ts-http-runtime/src/client/sendRequest.ts

@@ -73,7 +73,7 @@ export async function sendRequest(
  * @param options - request options InternalRequestParameters
  * @returns returns the content-type
  */
-function getRequestContentType(options: InternalRequestParameters = {}): string {
+function getRequestContentType(options: InternalRequestParameters = {}): string | undefined {
   return (
     options.contentType ??
     (options.headers?.["content-type"] as string) ??
@@ -88,6 +88,10 @@ function getRequestContentType(options: InternalRequestParameters = {}): string
  * @returns returns the content-type
  */
 function getContentType(body: any): string | undefined {
+  if (body === undefined) {
+    return undefined;
+  }
+
   if (ArrayBuffer.isView(body)) {
     return "application/octet-stream";
   }
@@ -116,15 +120,13 @@ function buildPipelineRequest(
 ): PipelineRequest {
   const requestContentType = getRequestContentType(options);
   const { body, multipartBody } = getRequestBody(options.body, requestContentType);
-  const hasContent = body !== undefined || multipartBody !== undefined;
 
   const headers = createHttpHeaders({
     ...(options.headers ? options.headers : {}),
     accept: options.accept ?? options.headers?.accept ?? "application/json",
-    ...(hasContent &&
-      requestContentType && {
-        "content-type": requestContentType,
-      }),
+    ...(requestContentType && {
+      "content-type": requestContentType,
+    }),
   });
 
   return createPipelineRequest({

sdk/core/ts-http-runtime/test/client/sendRequest.spec.ts

@@ -366,16 +366,28 @@ describe("sendRequest", () => {
     await sendRequest("POST", mockBaseUrl, mockPipeline, { contentType: "testContent", body: {} });
   });
 
-  it("should not set content-type if no body is present", async () => {
+  it("should set content-type via contentType option even without body", async () => {
     const mockPipeline: Pipeline = createEmptyPipeline();
     mockPipeline.sendRequest = async (_client, request) => {
-      assert.equal(request.headers.get("content-type"), undefined);
+      assert.equal(request.headers.get("content-type"), "testContent");
       return { headers: createHttpHeaders() } as PipelineResponse;
     };
 
     await sendRequest("POST", mockBaseUrl, mockPipeline, { contentType: "testContent" });
   });
 
+  it("should set content-type via headers option even without body", async () => {
+    const mockPipeline: Pipeline = createEmptyPipeline();
+    mockPipeline.sendRequest = async (_client, request) => {
+      assert.equal(request.headers.get("content-type"), "application/xml");
+      return { headers: createHttpHeaders() } as PipelineResponse;
+    };
+
+    await sendRequest("POST", mockBaseUrl, mockPipeline, {
+      headers: { "content-type": "application/xml" },
+    });
+  });
+
   it("should set custom accept", async () => {
     const mockPipeline: Pipeline = createEmptyPipeline();
     mockPipeline.sendRequest = async (_client, request) => {