Fix the duplicate usage flag value

packages/typespec-client-generator-core/src/interfaces.ts

@@ -638,7 +638,7 @@ export enum UsageFlags {
   // Set when model is used in conjunction with an application/json content type.
   Json = 1 << 8,
   // Set when model is used in conjunction with an application/xml content type.
-  Xml = 1 << 8,
+  Xml = 1 << 9,
 }
 
 interface SdkExampleBase {

packages/typespec-client-generator-core/src/types.ts

@@ -1568,7 +1568,7 @@ function updateTypesFromOperation(
         updateUsageOfModel(context, UsageFlags.Json, sdkType);
       }
       if (httpBody.contentTypes.some((x) => isXmlContentType(x))) {
-        updateUsageOfModel(context, UsageFlags.Json, sdkType);
+        updateUsageOfModel(context, UsageFlags.Xml, sdkType);
       }
       if (httpBody.contentTypes.includes("application/merge-patch+json")) {
         // will also have Json type

packages/typespec-client-generator-core/test/types/model-types.test.ts

@@ -1473,17 +1473,33 @@ describe("typespec-client-generator-core: model types", () => {
     await runner.compileAndDiagnose(`
         @service({})
         namespace MyService {
-          model Test {
+          model RoundTrip {
+            prop: string;
+          }
+
+          model Input {
             prop: string;
           }
 
-          op test(@header("content-type") contentType: "application/xml", @body body: Test): Test;
+          @route("/test1")
+          op test1(@header("content-type") contentType: "application/xml", @body body: RoundTrip): RoundTrip;
+
+          @route("/test2")
+          op test2(@header("content-type") contentType: "application/xml", @body body: Input): void;
         }
       `);
 
     const models = runner.context.sdkPackage.models;
-    strictEqual(models.length, 1);
-    strictEqual(models[0].name, "Test");
-    strictEqual(models[0].usage, UsageFlags.Input | UsageFlags.Output | UsageFlags.Xml);
+    strictEqual(models.length, 2);
+    const roundTripModel = models.find((x) => x.name === "RoundTrip");
+    const inputModel = models.find((x) => x.name === "Input");
+    ok(roundTripModel);
+    strictEqual(
+      roundTripModel.usage,
+      UsageFlags.Input | UsageFlags.Output | UsageFlags.Json | UsageFlags.Xml
+    );
+
+    ok(inputModel);
+    strictEqual(inputModel.usage, UsageFlags.Input | UsageFlags.Xml);
   });
 });

packages/typespec-client-generator-core/test/types/usage-flags.test.ts

@@ -0,0 +1,23 @@
+import { beforeEach, describe, expect, it } from "vitest";
+import { UsageFlags } from "../../src/interfaces.js";
+import { SdkTestRunner, createSdkTestRunner } from "../test-host.js";
+
+describe("typespec-client-generator-core: usage flags", () => {
+  let runner: SdkTestRunner;
+
+  beforeEach(async () => {
+    runner = await createSdkTestRunner({ emitterName: "@azure-tools/typespec-java" });
+  });
+
+  it("all possible values in UsageFlags should be orthogonal", async () => {
+    const values = Object.values(UsageFlags).filter(
+      (value) => typeof value === "number"
+    ) as number[];
+
+    for (let i = 0; i < values.length; i++) {
+      for (let j = i + 1; j < values.length; j++) {
+        expect(values[i] & values[j]).toBe(0);
+      }
+    }
+  });
+});