Add Spector case for Flatten property

packages/typespec-ts/package.json

@@ -69,7 +69,7 @@
     "@typespec/spector": "0.1.0-alpha.24-dev.2",
     "@typespec/spec-api": "0.1.0-dev.0",
     "@typespec/tspd": "0.74.0",
-    "@azure-tools/azure-http-specs": "0.1.0-alpha.38-dev.2",
+    "@azure-tools/azure-http-specs": "0.1.0-alpha.38-dev.4",
     "@azure-tools/typespec-autorest": "^0.65.0",
     "@azure-tools/typespec-azure-core": "^0.65.0",
     "@azure-tools/typespec-azure-resource-manager": "^0.65.0",

packages/typespec-ts/src/modular/helpers/operationHelpers.ts

@@ -1951,6 +1951,11 @@ function getSerializationExpressionForFlatten(
       !isReadOnly(p) &&
       !isMetadata(context.program, p.__raw!)
   );
+  // If all properties in the flattened model are read-only, omit the field entirely
+  // so it is not included in the serialized request body.
+  if (validProps.length === 0) {
+    return `undefined`;
+  }
   const optionalPrefix = property.optional
     ? `${resolveReference(SerializationHelpers.areAllPropsUndefined)}(${propertyPath}, [${validProps
         .map((p) => `"${p.name}"`)

packages/typespec-ts/src/modular/serialization/buildSerializerFunction.ts

@@ -502,9 +502,26 @@ function buildModelTypeSerializer(
         return ${serializeContent}
       `);
     } else {
-      output.push(`
-        return item;
-      `);
+      // For flatten properties, if all properties are readonly, return empty object
+      // Otherwise, return the item itself
+      if (options.flatten) {
+        // Change parameter name to _item to indicate it's intentionally unused
+        serializerFunction.parameters = [
+          {
+            name: "_item",
+            type: options.flatten
+              ? resolveReference(refkey(options.flatten.baseModel))
+              : resolveReference(refkey(type))
+          }
+        ];
+        output.push(`
+          return {};
+        `);
+      } else {
+        output.push(`
+          return item;
+        `);
+      }
     }
     serializerFunction.statements = output;
   }

packages/typespec-ts/test/azureIntegration/generated/azure/client-generator-core/flatten-property/src/index.d.ts

@@ -44,6 +44,16 @@ export declare type FlattenPropertyClient = Client & {
 export declare interface FlattenPropertyClientOptions extends ClientOptions {
 }
 
+export declare interface FlattenUnknownModel {
+    name: string;
+    properties?: unknown;
+}
+
+export declare interface FlattenUnknownModelOutput {
+    name: string;
+    properties?: any;
+}
+
 export declare interface NestedFlattenModel {
     name: string;
     properties: ChildFlattenModel;
@@ -69,6 +79,36 @@ export declare interface PutFlattenModelBodyParam {
 
 export declare type PutFlattenModelParameters = PutFlattenModelBodyParam & RequestParameters;
 
+export declare interface PutFlattenReadOnlyModel {
+    put(options: PutFlattenReadOnlyModelParameters): StreamableMethod<PutFlattenReadOnlyModel200Response>;
+}
+
+export declare interface PutFlattenReadOnlyModel200Response extends HttpResponse {
+    status: "200";
+    body: SolutionOutput;
+}
+
+export declare interface PutFlattenReadOnlyModelBodyParam {
+    body: Solution;
+}
+
+export declare type PutFlattenReadOnlyModelParameters = PutFlattenReadOnlyModelBodyParam & RequestParameters;
+
+export declare interface PutFlattenUnknownModel {
+    put(options: PutFlattenUnknownModelParameters): StreamableMethod<PutFlattenUnknownModel200Response>;
+}
+
+export declare interface PutFlattenUnknownModel200Response extends HttpResponse {
+    status: "200";
+    body: FlattenUnknownModelOutput;
+}
+
+export declare interface PutFlattenUnknownModelBodyParam {
+    body: FlattenUnknownModel;
+}
+
+export declare type PutFlattenUnknownModelParameters = PutFlattenUnknownModelBodyParam & RequestParameters;
+
 export declare interface PutNestedFlattenModel {
     put(options: PutNestedFlattenModelParameters): StreamableMethod<PutNestedFlattenModel200Response>;
 }
@@ -87,6 +127,29 @@ export declare type PutNestedFlattenModelParameters = PutNestedFlattenModelBodyP
 export declare interface Routes {
     (path: "/azure/client-generator-core/flatten-property/flattenModel"): PutFlattenModel;
     (path: "/azure/client-generator-core/flatten-property/nestedFlattenModel"): PutNestedFlattenModel;
+    (path: "/azure/client-generator-core/flatten-property/flattenUnknownModel"): PutFlattenUnknownModel;
+    (path: "/azure/client-generator-core/flatten-property/flattenReadOnlyModel"): PutFlattenReadOnlyModel;
+}
+
+export declare interface Solution {
+    name: string;
+    properties: SolutionProperties;
+    propertiesOptional?: SolutionProperties;
+}
+
+export declare interface SolutionOutput {
+    name: string;
+    properties: SolutionPropertiesOutput;
+    propertiesOptional?: SolutionPropertiesOutput;
+}
+
+export declare interface SolutionProperties {
+}
+
+export declare interface SolutionPropertiesOutput {
+    readonly solutionId?: string;
+    readonly title?: string;
+    readonly content?: string;
 }
 
 export { }

packages/typespec-ts/test/azureIntegration/modelFlatten.spec.ts

@@ -50,4 +50,37 @@ describe("Flatten Property Rest Client", () => {
     assert.strictEqual(result.body.properties.properties.description, "foo");
     assert.strictEqual(result.body.properties.properties.age, 1);
   });
+
+  it("should update and receive model with unknown flatten property", async () => {
+    const result = await client
+      .path("/azure/client-generator-core/flatten-property/flattenUnknownModel")
+      .put({
+        body: {
+          name: "foo"
+        }
+      });
+    assert.strictEqual(result.status, "200");
+    assert.strictEqual(result.body.name, "test");
+    assert.deepEqual(result.body.properties, {
+      key1: "value1",
+      key2: "value2"
+    });
+  });
+
+  it("should update and receive model with all readonly flatten properties", async () => {
+    const result = await client
+      .path(
+        "/azure/client-generator-core/flatten-property/flattenReadOnlyModel"
+      )
+      .put({
+        body: {
+          name: "foo"
+        } as any
+      });
+    assert.strictEqual(result.status, "200");
+    assert.strictEqual(result.body.name, "foo");
+    assert.strictEqual((result.body as any).solutionId, "solution1");
+    assert.strictEqual((result.body as any).title, "Solution Title");
+    assert.strictEqual((result.body as any).content, "Solution Content");
+  });
 });

packages/typespec-ts/test/azureModularIntegration/generated/azure/client-generator-core/flatten-property/src/index.d.ts

@@ -23,13 +23,20 @@ export declare class FlattenPropertyClient {
     private _client;
     readonly pipeline: Pipeline;
     constructor(options?: FlattenPropertyClientOptionalParams);
+    putFlattenReadOnlyModel(body: Solution, options?: PutFlattenReadOnlyModelOptionalParams): Promise<Solution>;
+    putFlattenUnknownModel(input: FlattenUnknownModel, options?: PutFlattenUnknownModelOptionalParams): Promise<FlattenUnknownModel>;
     putNestedFlattenModel(input: NestedFlattenModel, options?: PutNestedFlattenModelOptionalParams): Promise<NestedFlattenModel>;
     putFlattenModel(input: FlattenModel, options?: PutFlattenModelOptionalParams): Promise<FlattenModel>;
 }
 
 export declare interface FlattenPropertyClientOptionalParams extends ClientOptions {
 }
 
+export declare interface FlattenUnknownModel {
+    name: string;
+    properties?: any;
+}
+
 export declare interface NestedFlattenModel {
     name: string;
     summary: string;
@@ -39,7 +46,29 @@ export declare interface NestedFlattenModel {
 export declare interface PutFlattenModelOptionalParams extends OperationOptions {
 }
 
+export declare interface PutFlattenReadOnlyModelOptionalParams extends OperationOptions {
+}
+
+export declare interface PutFlattenUnknownModelOptionalParams extends OperationOptions {
+}
+
 export declare interface PutNestedFlattenModelOptionalParams extends OperationOptions {
 }
 
+export declare interface Solution {
+    name: string;
+    readonly solutionId?: string;
+    readonly title?: string;
+    readonly content?: string;
+    readonly solutionIdPropertiesOptionalSolutionId?: string;
+    readonly titlePropertiesOptionalTitle?: string;
+    readonly contentPropertiesOptionalContent?: string;
+}
+
+export declare interface SolutionProperties {
+    readonly solutionId?: string;
+    readonly title?: string;
+    readonly content?: string;
+}
+
 export { }

packages/typespec-ts/test/azureModularIntegration/modelFlatten.spec.ts

@@ -35,4 +35,23 @@ describe("Property Flatten Client", () => {
     assert.strictEqual(result.properties.description, "foo");
     assert.strictEqual(result.properties.age, 1);
   });
+
+  it("Update and receive model with unknown properties flattening", async () => {
+    const result = await client.putFlattenUnknownModel({
+      name: "foo"
+    });
+    assert.strictEqual(result.name, "test");
+    assert.strictEqual(result.properties?.key1, "value1");
+    assert.strictEqual(result.properties?.key2, "value2");
+  });
+
+  it("Update and receive model with read-only properties flattening", async () => {
+    const result = await client.putFlattenReadOnlyModel({
+      name: "foo"
+    });
+    assert.strictEqual(result.name, "foo");
+    assert.strictEqual(result.solutionId, "solution1");
+    assert.strictEqual(result.title, "Solution Title");
+    assert.strictEqual(result.content, "Solution Content");
+  });
 });

packages/typespec-ts/test/modularUnit/scenarios/models/serialization/readonlyFlattenModel.md

@@ -35,8 +35,6 @@ needTCGC: true
 ## Models
 
 ```ts models
-import { areAllPropsUndefined } from "../static-helpers/serialization/check-prop-undefined.js";
-
 /**
  * This file contains only generated model types and their (de)serializers.
  * Disable the following rules for internal models with '_' prefix and deserializers which require 'any' for raw JSON input.
@@ -54,12 +52,7 @@ export interface Solution {
 }
 
 export function solutionSerializer(item: Solution): any {
-  return {
-    properties: _solutionPropertiesSerializer(item),
-    propertiesOptional: areAllPropsUndefined(item, [])
-      ? undefined
-      : _solutionPropertiesOptionalSerializer(item),
-  };
+  return { properties: undefined, propertiesOptional: undefined };
 }
 
 /** model interface SolutionProperties */
@@ -73,11 +66,11 @@ export function solutionPropertiesSerializer(item: SolutionProperties): any {
   return item;
 }
 
-export function _solutionPropertiesSerializer(item: Solution): any {
-  return item;
+export function _solutionPropertiesSerializer(_item: Solution): any {
+  return {};
 }
 
-export function _solutionPropertiesOptionalSerializer(item: Solution): any {
-  return item;
+export function _solutionPropertiesOptionalSerializer(_item: Solution): any {
+  return {};
 }
 ```