Fix action handling for no contents

packages/binding-http/src/routes/action.ts

@@ -83,7 +83,7 @@ export default async function actionRoute(
                 res.writeHead(200);
                 output.body.pipe(res);
             } else {
-                res.writeHead(200);
+                res.writeHead(204);
                 res.end();
             }
         } catch (err) {

packages/binding-http/test/http-server-test.ts

@@ -213,6 +213,36 @@ class HttpServerTest {
         return httpServer.stop();
     }
 
+    @test async "should return 204 when action has not output"() {
+        const httpServer = new HttpServer({ port: 0 });
+
+        await httpServer.start(null);
+
+        const testThing = new ExposedThing(null, {
+            title: "Test",
+            actions: {
+                noOutput: {
+                    output: { type: "string" },
+                    forms: [],
+                },
+            },
+        });
+
+        testThing.setActionHandler("noOutput", async () => undefined);
+
+        await httpServer.expose(testThing);
+
+        const uri = `http://localhost:${httpServer.getPort()}/test/`;
+
+        debug(`Testing ${uri}`);
+
+        const resp = await fetch(uri + "actions/noOutput", { method: "POST" });
+
+        expect(resp.status).to.equal(204);
+
+        return httpServer.stop();
+    }
+
     @test async "should check uriVariables consistency"() {
         const httpServer = new HttpServer({ port: 0 });
 

packages/core/src/exposed-thing.ts

@@ -369,7 +369,7 @@ export default class ExposedThing extends TD.Thing implements WoT.ExposedThing {
                     new InteractionOutput(inputContent, form, this.actions[name].input),
                     options
                 );
-                if (result) {
+                if (result !== undefined) {
                     // TODO: handle form.response.contentType
                     return ContentManager.valueToContent(result, this.actions[name].output, form.contentType);
                 }

packages/core/test/ServerTest.ts

@@ -1022,6 +1022,39 @@ class WoTServerTest {
         callback.should.have.been.called();
     }
 
+    @test async "should return content when returning 0 for action handler"() {
+        const thing = await WoTServerTest.WoT.produce({
+            title: "The Machine",
+            actions: {
+                test: {
+                    output: {
+                        type: "number",
+                    },
+                    forms: [
+                        {
+                            href: "http://example.org/test",
+                            op: ["invokeaction"],
+                        },
+                    ],
+                },
+            },
+        });
+        const callback = spy(async (params: InteractionOutput) => {
+            return 0;
+        });
+
+        thing.setActionHandler("test", callback);
+
+        const result = await (<ExposedThing>thing).handleInvokeAction(
+            "test",
+            new Content("application/json", Readable.from(Buffer.from(""))),
+            { formIndex: 0 }
+        );
+
+        callback.should.have.been.called();
+        expect(result).to.be.instanceOf(Content);
+    }
+
     @test async "should fail due to wrong uriVariable"() {
         const thing = await WoTServerTest.WoT.produce({
             title: "The Machine",