[http-server-js] handle Scalar and value literal return types in result processing

packages/http-server-js/src/http/server/index.ts

@@ -580,6 +580,25 @@ function* emitResultProcessingForType(
     }
   }
 
+  if (target.kind === "Scalar" || isValueLiteralType(target)) {
+    const serializationRequired =
+      target.kind === "Scalar" && isSerializationRequired(ctx, module, target, "application/json");
+
+    if (target.kind === "Scalar") {
+      requireSerialization(ctx, target, "application/json");
+    }
+
+    yield `${names.ctx}.response.setHeader("content-type", "application/json");`;
+
+    if (serializationRequired) {
+      yield `${names.ctx}.response.end(globalThis.JSON.stringify(${transposeExpressionToJson(ctx, target, names.result, module)}));`;
+    } else {
+      yield `${names.ctx}.response.end(globalThis.JSON.stringify(${names.result}));`;
+    }
+
+    return;
+  }
+
   if (target.kind !== "Model") {
     throw new UnimplementedError(`result processing for type kind '${target.kind}'`);
   }

packages/http-server-js/test/scalar.test.ts

@@ -1,15 +1,22 @@
-import { ModelProperty, NoTarget, Scalar } from "@typespec/compiler";
-import { BasicTestRunner, createTestRunner } from "@typespec/compiler/testing";
+import { ModelProperty, NoTarget, Scalar, resolvePath } from "@typespec/compiler";
+import { BasicTestRunner, createTestRunner, createTester } from "@typespec/compiler/testing";
 import { deepStrictEqual, strictEqual } from "assert";
-import { beforeEach, describe, it } from "vitest";
+import { beforeEach, describe, expect, it } from "vitest";
 import { getJsScalar } from "../src/common/scalar.js";
-import { createPathCursor, JsContext, Module } from "../src/ctx.js";
+import { JsContext, Module, createPathCursor } from "../src/ctx.js";
 
 import { module as dateTimeModule } from "../generated-defs/helpers/datetime.js";
 import { module as temporalHelpersModule } from "../generated-defs/helpers/temporal/native.js";
 import { module as temporalPolyfillHelpersModule } from "../generated-defs/helpers/temporal/polyfill.js";
 import { JsEmitterOptions } from "../src/lib.js";
 
+const HttpServerEmitterTester = createTester(resolvePath(import.meta.dirname, ".."), {
+  libraries: ["@typespec/http", "@typespec/http-server-js"],
+})
+  .import("@typespec/http")
+  .using("Http")
+  .emit("@typespec/http-server-js");
+
 describe("scalar", () => {
   let runner: BasicTestRunner;
 
@@ -186,6 +193,22 @@ describe("scalar", () => {
     );
   });
 
+  it("emits result processing for bare scalar responses", async () => {
+    const { outputs } = await HttpServerEmitterTester.compile(`
+      @service(#{ title: "Example" })
+      @route("/")
+      namespace Example {
+        @get op read(): string;
+      }
+    `);
+
+    const serverRaw = outputs["src/generated/http/operations/server-raw.ts"];
+
+    expect(serverRaw).toBeDefined();
+    expect(serverRaw).toContain('response.setHeader("content-type", "application/json");');
+    expect(serverRaw).toMatch(/response\.end\(globalThis\.JSON\.stringify\(__result_\d+\)\);/);
+  });
+
   describe("date/time/duration types", () => {
     describe("mode: temporal", () => {
       const options: JsEmitterOptions = {