[Backport 2.x] Infer edges from previous node inputs

src/main/java/org/opensearch/flowframework/model/Workflow.java

@@ -19,6 +19,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
+import java.util.stream.Collectors;
 
 import static org.opensearch.core.xcontent.XContentParserUtils.ensureExpectedToken;
 
@@ -119,13 +120,14 @@ public static Workflow parse(XContentParser parser) throws IOException {
         if (nodes.isEmpty()) {
             throw new IOException("A workflow must have at least one node.");
         }
-        if (edges.isEmpty()) {
-            // infer edges from sequence of nodes
-            // Start iteration at 1, will skip for a one-node array
-            for (int i = 1; i < nodes.size(); i++) {
-                edges.add(new WorkflowEdge(nodes.get(i - 1).id(), nodes.get(i).id()));
-            }
-        }
+        // Iterate the nodes and infer edges from previous node inputs
+        List<WorkflowEdge> inferredEdges = nodes.stream()
+            .flatMap(node -> node.previousNodeInputs().keySet().stream().map(previousNode -> new WorkflowEdge(previousNode, node.id())))
+            .collect(Collectors.toList());
+        // Remove any that are already in edges list
+        inferredEdges.removeAll(edges);
+        // Then add them to the edges
+        edges.addAll(inferredEdges);
         return new Workflow(userParams, nodes, edges);
     }
 

src/test/java/org/opensearch/flowframework/model/TemplateTestJsonUtil.java

@@ -17,6 +17,7 @@
 import org.opensearch.flowframework.workflow.NoOpStep;
 
 import java.io.IOException;
+import java.util.Arrays;
 import java.util.List;
 import java.util.stream.Collectors;
 
@@ -53,6 +54,22 @@ public static String nodeWithTypeAndTimeout(String id, String type, String timeo
             + "\"}}";
     }
 
+    public static String nodeWithTypeAndPreviousNodes(String id, String type, String... previousNodes) {
+        return "{\""
+            + WorkflowNode.ID_FIELD
+            + "\": \""
+            + id
+            + "\", \""
+            + WorkflowNode.TYPE_FIELD
+            + "\": \""
+            + type
+            + "\", \""
+            + WorkflowNode.PREVIOUS_NODE_INPUTS_FIELD
+            + "\": {"
+            + Arrays.stream(previousNodes).map(n -> "\"" + n + "\": \"output_value\"").collect(Collectors.joining(","))
+            + "}}";
+    }
+
     public static String edge(String sourceId, String destId) {
         return "{\"" + WorkflowEdge.SOURCE_FIELD + "\": \"" + sourceId + "\", \"" + WorkflowEdge.DEST_FIELD + "\": \"" + destId + "\"}";
     }

src/test/java/org/opensearch/flowframework/rest/FlowFrameworkRestApiIT.java

@@ -140,7 +140,7 @@ public void testCreateAndProvisionRemoteModelWorkflow() throws Exception {
         Workflow cyclicalWorkflow = new Workflow(
             originalWorkflow.userParams(),
             originalWorkflow.nodes(),
-            List.of(new WorkflowEdge("workflow_step_1", "workflow_step_2"), new WorkflowEdge("workflow_step_2", "workflow_step_1"))
+            List.of(new WorkflowEdge("workflow_step_2", "workflow_step_3"), new WorkflowEdge("workflow_step_3", "workflow_step_2"))
         );
 
         Template cyclicalTemplate = new Template.Builder().name(template.name())
@@ -155,7 +155,10 @@ public void testCreateAndProvisionRemoteModelWorkflow() throws Exception {
 
         // Hit dry run
         ResponseException exception = expectThrows(ResponseException.class, () -> createWorkflowValidation(cyclicalTemplate));
-        assertTrue(exception.getMessage().contains("Cycle detected: [workflow_step_2->workflow_step_1, workflow_step_1->workflow_step_2]"));
+        // output order not guaranteed
+        assertTrue(exception.getMessage().contains("Cycle detected"));
+        assertTrue(exception.getMessage().contains("workflow_step_2->workflow_step_3"));
+        assertTrue(exception.getMessage().contains("workflow_step_3->workflow_step_2"));
 
         // Hit Create Workflow API with original template
         Response response = createWorkflow(template);

src/test/java/org/opensearch/flowframework/workflow/WorkflowProcessSorterTests.java

@@ -24,7 +24,6 @@
 import org.opensearch.common.unit.TimeValue;
 import org.opensearch.core.action.ActionListener;
 import org.opensearch.core.rest.RestStatus;
-import org.opensearch.core.xcontent.XContentParser;
 import org.opensearch.flowframework.common.FlowFrameworkSettings;
 import org.opensearch.flowframework.exception.FlowFrameworkException;
 import org.opensearch.flowframework.indices.FlowFrameworkIndicesHandler;
@@ -59,6 +58,7 @@
 import static org.opensearch.flowframework.model.TemplateTestJsonUtil.edge;
 import static org.opensearch.flowframework.model.TemplateTestJsonUtil.node;
 import static org.opensearch.flowframework.model.TemplateTestJsonUtil.nodeWithType;
+import static org.opensearch.flowframework.model.TemplateTestJsonUtil.nodeWithTypeAndPreviousNodes;
 import static org.opensearch.flowframework.model.TemplateTestJsonUtil.nodeWithTypeAndTimeout;
 import static org.opensearch.flowframework.model.TemplateTestJsonUtil.workflow;
 import static org.mockito.ArgumentMatchers.any;
@@ -72,11 +72,14 @@ public class WorkflowProcessSorterTests extends OpenSearchTestCase {
     private static final String NO_START_NODE_DETECTED = "No start node detected: all nodes have a predecessor.";
     private static final String CYCLE_DETECTED = "Cycle detected:";
 
+    // Wrap parser into workflow
+    private static Workflow parseToWorkflow(String json) throws IOException {
+        return Workflow.parse(TemplateTestJsonUtil.jsonToParser(json));
+    }
+
     // Wrap parser into node list
     private static List<ProcessNode> parseToNodes(String json) throws IOException {
-        XContentParser parser = TemplateTestJsonUtil.jsonToParser(json);
-        Workflow w = Workflow.parse(parser);
-        return workflowProcessSorter.sortProcessNodes(w, "123");
+        return workflowProcessSorter.sortProcessNodes(parseToWorkflow(json), "123");
     }
 
     // Wrap parser into string list
@@ -242,6 +245,56 @@ public void testNoEdges() throws IOException {
         assertTrue(workflow.contains("B"));
     }
 
+    public void testInferredEdges() throws IOException {
+        Workflow w = parseToWorkflow(
+            workflow(List.of(nodeWithTypeAndPreviousNodes("A", "noop"), nodeWithTypeAndPreviousNodes("B", "noop")), Collections.emptyList())
+        );
+        assertTrue(w.edges().isEmpty());
+
+        w = parseToWorkflow(
+            workflow(List.of(nodeWithTypeAndPreviousNodes("A", "noop"), nodeWithTypeAndPreviousNodes("B", "noop")), List.of(edge("B", "A")))
+        );
+        // edge from previous inputs only
+        assertEquals(List.of(new WorkflowEdge("B", "A")), w.edges());
+
+        w = parseToWorkflow(
+            workflow(
+                List.of(nodeWithTypeAndPreviousNodes("A", "noop", "B"), nodeWithTypeAndPreviousNodes("B", "noop")),
+                Collections.emptyList()
+            )
+        );
+        // edge from edges only
+        assertEquals(List.of(new WorkflowEdge("B", "A")), w.edges());
+
+        w = parseToWorkflow(
+            workflow(
+                List.of(
+                    nodeWithTypeAndPreviousNodes("A", "noop", "B"),
+                    nodeWithTypeAndPreviousNodes("B", "noop"),
+                    nodeWithTypeAndPreviousNodes("C", "noop")
+                ),
+                List.of(edge("C", "A"))
+            )
+        );
+        // combine sources, order not guaranteed
+        assertEquals(2, w.edges().size());
+        assertTrue(w.edges().contains(new WorkflowEdge("B", "A")));
+        assertTrue(w.edges().contains(new WorkflowEdge("C", "A")));
+
+        w = parseToWorkflow(
+            workflow(
+                List.of(
+                    nodeWithTypeAndPreviousNodes("A", "noop", "B"),
+                    nodeWithTypeAndPreviousNodes("B", "noop"),
+                    nodeWithTypeAndPreviousNodes("C", "noop")
+                ),
+                List.of(edge("B", "A"))
+            )
+        );
+        // duplicates, only 1
+        assertEquals(List.of(new WorkflowEdge("B", "A")), w.edges());
+    }
+
     public void testExceptions() throws IOException {
         Exception ex = assertThrows(
             FlowFrameworkException.class,