Add basic input/output metadata to discovery

Author: slinkydeveloper

sdk-api-kotlin/src/main/kotlin/dev/restate/sdk/kotlin/KtSerdes.kt

@@ -53,6 +53,10 @@ object KtSerdes {
         override fun deserialize(byteString: ByteString) {
           return
         }
+
+        override fun contentType(): String? {
+          return null
+        }
       }
 
   /** Creates a [Serde] implementation using the `kotlinx.serialization` json module. */
@@ -65,6 +69,10 @@ object KtSerdes {
       override fun deserialize(value: ByteArray?): T {
         return Json.decodeFromString(serializer, String(value!!, StandardCharsets.UTF_8))
       }
+
+      override fun contentType(): String {
+        return "application/json"
+      }
     }
   }
 }

sdk-api-kotlin/src/main/kotlin/dev/restate/sdk/kotlin/Service.kt

@@ -121,7 +121,14 @@ private constructor(
       private val LOG = LogManager.getLogger()
     }
 
-    fun toHandlerDefinition() = HandlerDefinition(handlerSignature.name, handlerType, this)
+    fun toHandlerDefinition() =
+        HandlerDefinition(
+            handlerSignature.name,
+            handlerType,
+            handlerSignature.requestSerde.contentType() != null,
+            handlerSignature.requestSerde.contentType(),
+            handlerSignature.responseSerde.contentType(),
+            this)
 
     override fun handle(
         syscalls: Syscalls,

sdk-api/src/main/java/dev/restate/sdk/Service.java

@@ -132,7 +132,13 @@ public BiFunction<Context, REQ, RES> getRunner() {
     }
 
     public HandlerDefinition<Service.Options> toHandlerDefinition() {
-      return new HandlerDefinition<>(this.handlerSignature.name, this.handlerType, this);
+      return new HandlerDefinition<>(
+          this.handlerSignature.name,
+          this.handlerType,
+          this.handlerSignature.requestSerde.contentType() != null,
+          this.handlerSignature.requestSerde.contentType(),
+          this.handlerSignature.responseSerde.contentType(),
+          this);
     }
 
     @Override

sdk-common/src/main/java/dev/restate/sdk/common/syscalls/HandlerDefinition.java

@@ -10,15 +10,28 @@
 
 import dev.restate.sdk.common.HandlerType;
 import java.util.Objects;
+import org.jspecify.annotations.Nullable;
 
 public final class HandlerDefinition<O> {
   private final String name;
   private final HandlerType handlerType;
+  private final boolean inputRequired;
+  private final @Nullable String acceptInputContentType;
+  private final @Nullable String returnedContentType;
   private final InvocationHandler<O> handler;
 
-  public HandlerDefinition(String name, HandlerType handlerType, InvocationHandler<O> handler) {
+  public HandlerDefinition(
+      String name,
+      HandlerType handlerType,
+      boolean inputRequired,
+      @Nullable String acceptInputContentType,
+      @Nullable String returnedContentType,
+      InvocationHandler<O> handler) {
     this.name = name;
     this.handlerType = handlerType;
+    this.inputRequired = inputRequired;
+    this.acceptInputContentType = acceptInputContentType;
+    this.returnedContentType = returnedContentType;
     this.handler = handler;
   }
 
@@ -30,6 +43,18 @@ public HandlerType getHandlerType() {
     return handlerType;
   }
 
+  public boolean isInputRequired() {
+    return inputRequired;
+  }
+
+  public String getAcceptInputContentType() {
+    return acceptInputContentType;
+  }
+
+  public String getReturnedContentType() {
+    return returnedContentType;
+  }
+
   public InvocationHandler<O> getHandler() {
     return handler;
   }

sdk-core/src/main/java/dev/restate/sdk/core/DeploymentManifest.java

@@ -10,14 +10,15 @@
 
 import dev.restate.sdk.common.HandlerType;
 import dev.restate.sdk.common.ServiceType;
+import dev.restate.sdk.common.syscalls.HandlerDefinition;
 import dev.restate.sdk.common.syscalls.ServiceDefinition;
-import dev.restate.sdk.core.manifest.DeploymentManifestSchema;
-import dev.restate.sdk.core.manifest.Handler;
-import dev.restate.sdk.core.manifest.Service;
+import dev.restate.sdk.core.manifest.*;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 final class DeploymentManifest {
+  private static final Input EMPTY_INPUT = new Input();
+  private static final Output EMPTY_OUTPUT = new Output().withSetContentTypeIfEmpty(false);
 
   private final DeploymentManifestSchema manifest;
 
@@ -37,12 +38,7 @@ public DeploymentManifest(
                                 .withTy(convertServiceType(svc.getServiceType()))
                                 .withHandlers(
                                     svc.getHandlers().stream()
-                                        .map(
-                                            method ->
-                                                new Handler()
-                                                    .withTy(
-                                                        convertHandlerType(method.getHandlerType()))
-                                                    .withName(method.getName()))
+                                        .map(DeploymentManifest::convertHandler)
                                         .collect(Collectors.toList())))
                     .collect(Collectors.toList()));
   }
@@ -62,6 +58,24 @@ private static Service.Ty convertServiceType(ServiceType serviceType) {
     throw new IllegalStateException();
   }
 
+  private static Handler convertHandler(HandlerDefinition<?> handler) {
+    return new Handler()
+        .withName(handler.getName())
+        .withTy(convertHandlerType(handler.getHandlerType()))
+        .withInput(
+            handler.getAcceptInputContentType() == null
+                ? EMPTY_INPUT
+                : new Input()
+                    .withRequired(handler.isInputRequired())
+                    .withContentType(handler.getAcceptInputContentType()))
+        .withOutput(
+            handler.getReturnedContentType() == null
+                ? EMPTY_OUTPUT
+                : new Output()
+                    .withContentType(handler.getReturnedContentType())
+                    .withSetContentTypeIfEmpty(false));
+  }
+
   private static Handler.Ty convertHandlerType(HandlerType handlerType) {
     switch (handlerType) {
       case EXCLUSIVE:

sdk-core/src/test/java/dev/restate/sdk/core/ComponentDiscoveryHandlerTest.java

@@ -32,7 +32,14 @@ void handleWithMultipleServices() {
                 new ServiceDefinition<>(
                     "MyGreeter",
                     ServiceType.SERVICE,
-                    List.of(new HandlerDefinition<>("greet", HandlerType.EXCLUSIVE, null)))));
+                    List.of(
+                        new HandlerDefinition<>(
+                            "greet",
+                            HandlerType.EXCLUSIVE,
+                            false,
+                            "application/json",
+                            "application/json",
+                            null)))));
 
     DeploymentManifestSchema manifest = deploymentManifest.manifest();