fix(app): throw error when trying to return function or symbol as response

Author: pi0

src/app.ts

@@ -236,5 +236,9 @@ function handleHandlerResponse(event: H3Event, val: any, jsonSpace?: number) {
     return send(event, val.toString(), MIMES.json);
   }
 
-  return false;
+  // Symbol or Function (undefined is already handled by consumer)
+  throw createError({
+    statusCode: 500,
+    statusMessage: `[h3] Cannot send ${valType} as response.`,
+  });
 }

test/app.test.ts

@@ -39,6 +39,33 @@ describe("app", () => {
     expect(res.text).toBe("9007199254740991");
   });
 
+  it("throws error when returning symbol or function", async () => {
+    app.use(
+      "/fn",
+      eventHandler(() => {
+        return function foo() {};
+      })
+    );
+    app.use(
+      "/symbol",
+      eventHandler(() => {
+        return Symbol.for("foo");
+      })
+    );
+
+    const resFn = await request.get("/fn");
+    expect(resFn.status).toBe(500);
+    expect(resFn.body.statusMessage).toBe(
+      "[h3] Cannot send function as response."
+    );
+
+    const resSymbol = await request.get("/symbol");
+    expect(resSymbol.status).toBe(500);
+    expect(resSymbol.body.statusMessage).toBe(
+      "[h3] Cannot send symbol as response."
+    );
+  });
+
   it("can return Response directly", async () => {
     app.use(
       "/",