allow ErrorHandler to provide an alternate result

Author: Kaleidox

src/main/java/org/comroid/api/tree/Component.java

@@ -105,8 +105,8 @@ default String getFullName() {
 
     @Override
     default <T extends Component> Stream<T> components(@Nullable Class<? super T> type) {
-        return Stream.concat(streamChildren(type),
-                isSubComponent() ? Stream.of(getParent()).filter(Objects::nonNull).flatMap(comp -> comp.components(type)) : empty());
+        return Stream.<T>concat(streamChildren(type),
+                isSubComponent() ? Stream.of(getParent()).filter(Objects::nonNull).flatMap(comp -> comp.components(type)) : empty()).distinct();
     }
 
     @Override

src/main/java/org/comroid/interaction/InteractionCore.java

@@ -4,10 +4,8 @@
 import lombok.extern.java.Log;
 import org.comroid.api.tree.Component;
 import org.comroid.interaction.component.RegistryHandler;
-import org.comroid.interaction.component.error.ErrorHandler;
 import org.comroid.interaction.component.response.ResponseConverter;
 import org.comroid.interaction.component.response.ResponseHandler;
-import org.comroid.interaction.model.InteractionContext;
 import org.comroid.interaction.model.InteractionTree;
 import org.comroid.interaction.registry.InstanceRegistry;
 import org.comroid.interaction.registry.RegistrySource;
@@ -17,7 +15,6 @@
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.Set;
-import java.util.logging.Level;
 
 @Log
 @Value
@@ -59,16 +56,4 @@ public void register(Object target) {
     private void verifyComponentExists(Class<?> type) {
         component(type).assertion("No component of type %s was found".formatted(type.getCanonicalName()));
     }
-
-    public void handle(InteractionContext context, Throwable error) {
-        log.log(Level.SEVERE, "Encountered an error during interaction handling", error);
-
-        var handlers = (context == null ? components(ErrorHandler.class) : context.components(ErrorHandler.class)).iterator();
-        if (!handlers.hasNext()) return;
-
-        do {
-            var state = handlers.next().handle(context, error);
-            if (state != ErrorHandler.State.UNCHANGED) break;
-        } while (handlers.hasNext());
-    }
 }

src/main/java/org/comroid/interaction/adapter/stdio/StreamAdapter.java

@@ -19,6 +19,7 @@
 import java.util.Objects;
 import java.util.Queue;
 import java.util.concurrent.LinkedBlockingQueue;
+import java.util.logging.Level;
 
 @Log
 @Value
@@ -119,7 +120,8 @@ public void run() {
                 (context = createContext(line)).invoke();
                 output.write("> ");
             } catch (Throwable t) {
-                core.handle(context, t);
+                if (context != null) context.handle(t);
+                else log.log(Level.SEVERE, "An error occurred during initialization", t);
             }
         }
     }

src/main/java/org/comroid/interaction/component/error/ErrorHandler.java

@@ -4,7 +4,5 @@
 import org.jspecify.annotations.Nullable;
 
 public interface ErrorHandler {
-    State handle(@Nullable InteractionContext context, Throwable error);
-
-    enum State {UNCHANGED, RECOVERED}
+    @Nullable Object handle(@Nullable InteractionContext context, Throwable error);
 }

src/main/java/org/comroid/interaction/model/InteractionContext.java

@@ -8,6 +8,7 @@
 import org.comroid.api.tree.Component;
 import org.comroid.eval.MinimalExpression;
 import org.comroid.interaction.InteractionCore;
+import org.comroid.interaction.component.error.ErrorHandler;
 import org.comroid.interaction.component.response.ResponseConverter;
 import org.comroid.interaction.component.response.ResponseHandler;
 import org.comroid.interaction.node.MethodNode;
@@ -21,6 +22,7 @@
 import java.util.Objects;
 import java.util.concurrent.CompletableFuture;
 import java.util.function.Supplier;
+import java.util.logging.Level;
 
 @Log
 @Value
@@ -99,31 +101,41 @@ public void invoke() {
         if (node.getInteraction().async()) {
             component(ResponseHandler.class).ifPresent(it -> it.deferResponse(this));
 
-            CompletableFuture.supplyAsync(() -> node.invoke(this)).thenAccept(this::handleResponse).exceptionally(t -> {
-                core.handle(this, t);
+            CompletableFuture.supplyAsync(() -> node.invoke(this)).thenAccept(this::handle).exceptionally(t -> {
+                handle(t);
                 return null;
             });
         } else try {
             var response = node.invoke(this);
 
-            handleResponse(response);
+            handle(response);
         } catch (Throwable t) {
-            core.handle(this, t);
+            handle(t);
         }
     }
 
     @SuppressWarnings("unchecked")
-    private void handleResponse(final Object response) {
-        components(ResponseConverter.class).distinct()
-                .map(converter -> converter.convertResponse(response))
-                .distinct()
-                .filter(Objects::nonNull)
-                .forEach(formatted -> {
-                    var fType = formatted.getClass();
-                    components(ResponseHandler.class).distinct()
-                            .filter(handler -> handler.getResponseType().isAssignableFrom(fType))
-                            .forEach(handler -> handler.sendResponse(this, formatted));
-                });
+    private void handle(final Object response) {
+        components(ResponseConverter.class).map(converter -> converter.convertResponse(response)).distinct().filter(Objects::nonNull).forEach(formatted -> {
+            var fType = formatted.getClass();
+            components(ResponseHandler.class).filter(handler -> handler.getResponseType().isAssignableFrom(fType))
+                    .forEach(handler -> handler.sendResponse(this, formatted));
+        });
+    }
+
+    public void handle(Throwable error) {
+        log.log(Level.SEVERE, "Encountered an error during interaction handling", error);
+
+        var handlers = components(ErrorHandler.class).iterator();
+        if (!handlers.hasNext()) return;
+
+        Object response;
+
+        do {
+            response = handlers.next().handle(this, error);
+        } while (response == null && handlers.hasNext());
+
+        if (response != null) handle(response);
     }
 
     private static Supplier<RuntimeException> noSuchCommand(String name) {