[tcgc] add UsageFlags.JsonMergePatch

.chronus/changes/move_patch_to_usage-2024-2-20-15-40-32.md

@@ -0,0 +1,7 @@
+---
+changeKind: feature
+packages:
+  - "@azure-tools/typespec-client-generator-core"
+---
+
+We've added Usage.JsonMergePatch. Usage.Input continues to refer to all inputs, Usage.JsonMergePatch is set if a model is explicitly set as JSON merge patch input body

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

@@ -535,4 +535,5 @@ export enum UsageFlags {
   Input = 1 << 1,
   Output = 1 << 2,
   Versioning = 1 << 3,
+  JsonMergePatch = 1 << 4,
 }

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

@@ -1338,14 +1338,18 @@ function updateTypesFromOperation(
       });
     }
   }
-  if (httpOperation.parameters.body) {
-    const bodies = diagnostics.pipe(
-      checkAndGetClientType(context, httpOperation.parameters.body.type, operation)
-    );
+  const httpBody = httpOperation.parameters.body;
+  if (httpBody) {
+    const bodies = diagnostics.pipe(checkAndGetClientType(context, httpBody.type, operation));
     if (generateConvenient) {
       bodies.forEach((body) => {
         updateUsageOfModel(context, UsageFlags.Input, body);
       });
+      if (httpBody.contentTypes.includes("application/merge-patch+json")) {
+        bodies.forEach((body) => {
+          updateUsageOfModel(context, UsageFlags.JsonMergePatch, body);
+        });
+      }
     }
   }
   for (const response of httpOperation.responses) {

packages/typespec-client-generator-core/test/decorators.test.ts

@@ -4,7 +4,6 @@ import {
   Model,
   Namespace,
   Operation,
-  UsageFlags,
   ignoreDiagnostics,
 } from "@typespec/compiler";
 import { expectDiagnostics } from "@typespec/compiler/testing";
@@ -22,7 +21,7 @@ import {
   shouldGenerateConvenient,
   shouldGenerateProtocol,
 } from "../src/decorators.js";
-import { SdkOperationGroup } from "../src/interfaces.js";
+import { SdkOperationGroup, UsageFlags } from "../src/interfaces.js";
 import { getCrossLanguageDefinitionId, getCrossLanguagePackageId } from "../src/public-utils.js";
 import { getAllModels } from "../src/types.js";
 import { SdkTestRunner, createSdkContextTestHelper, createSdkTestRunner } from "./test-host.js";
@@ -2248,6 +2247,37 @@ describe("typespec-client-generator-core: decorators", () => {
 
       strictEqual(getUsage(runner.context, Dog), UsageFlags.Output);
     });
+
+    it("patch usage", async () => {
+      const { PatchModel, JsonMergePatchModel } = (await runner.compile(`
+        @service({})
+        @test namespace MyService {
+          @test
+          model PatchModel {
+            age: int32;
+          }
+
+          @test
+          model JsonMergePatchModel {
+            prop: string
+          }
+
+          @patch
+          @route("/patch")
+          op patchModel(@body body: PatchModel): void;
+
+          @patch
+          @route("/jsonMergePatch")
+          op jsonMergePatchModel(@body body: JsonMergePatchModel, @header contentType: "application/merge-patch+json"): void;
+        }
+      `)) as { PatchModel: Model; JsonMergePatchModel: Model };
+
+      strictEqual(getUsage(runner.context, PatchModel), UsageFlags.Input);
+      strictEqual(
+        getUsage(runner.context, JsonMergePatchModel),
+        UsageFlags.JsonMergePatch | UsageFlags.Input
+      );
+    });
   });
 
   describe("@flattenProperty", () => {