[Agent Builder] fix workflow tools returning empty output (elastic#242046)

## Summary

Fix elastic/search-team#11763
Follow-up of elastic#241040

Fix a bug in the `getWorkflowOutput` logic which was causing it to
return empty output because workflows no longer have an initial empty
scopeStack.

(not backporting because workflow behave may be different on 9.2 and the
initial PR wasn't backported)

Author: pgayvallet

x-pack/platform/plugins/shared/onechat/server/services/tools/tool_types/workflow/execute_workflow.ts

@@ -6,79 +6,18 @@
  */
 
 import type { KibanaRequest } from '@kbn/core-http-server';
-import {
-  ExecutionStatus as WorkflowExecutionStatus,
-  type WorkflowStepExecutionDto,
-} from '@kbn/workflows/types/v1';
+import { ExecutionStatus as WorkflowExecutionStatus } from '@kbn/workflows/types/v1';
 import type { WorkflowsServerPluginSetup } from '@kbn/workflows-management-plugin/server';
 import type { ToolHandlerResult } from '@kbn/onechat-server/tools';
 import { ToolResultType } from '@kbn/onechat-common/tools';
-import type { JsonValue } from '@kbn/utility-types';
+import { getWorkflowOutput } from './get_workflow_output';
 
 type WorkflowApi = WorkflowsServerPluginSetup['management'];
 
 const WORKFLOW_MAX_WAIT = 60_000;
 const WORKFLOW_INITIAL_WAIT = 1000;
 const WORKFLOW_CHECK_INTERVAL = 2_500;
 
-/**
- * Recursively extracts the output from a workflow execution's step executions.
- * At top-level (scopeDepth=0), finds the last step. At nested levels (scopeDepth>0),
- * considers all steps at that level. If steps have children, recurses into them.
- * Otherwise, returns their output(s).
- */
-export const getWorkflowOutput = (
-  stepExecutions: WorkflowStepExecutionDto[],
-  scopeDepth: number = 0
-): JsonValue => {
-  if (stepExecutions.length === 0) {
-    return null;
-  }
-
-  // Filter for steps at the current scope depth
-  const stepsAtThisLevel = stepExecutions.filter((step) => step.scopeStack.length === scopeDepth);
-
-  if (stepsAtThisLevel.length === 0) {
-    return null;
-  }
-
-  // At top-level (scopeDepth = 0), only consider the last step
-  // At nested levels (scopeDepth > 0), consider all steps
-  const stepsToProcess =
-    scopeDepth === 0 ? [stepsAtThisLevel[stepsAtThisLevel.length - 1]] : stepsAtThisLevel;
-
-  // Find all children of the steps we're processing
-  const children = stepExecutions.filter((step) => {
-    if (step.scopeStack.length !== scopeDepth + 1) return false;
-    const lastFrame = step.scopeStack[step.scopeStack.length - 1];
-    return stepsToProcess.some((parentStep) => lastFrame.stepId === parentStep.stepId);
-  });
-
-  // If there are children, recurse into them
-  // Pass only descendants (steps that have any of stepsToProcess in their scopeStack)
-  if (children.length > 0) {
-    const descendants = stepExecutions.filter((step) =>
-      step.scopeStack.some((frame) =>
-        stepsToProcess.some((parentStep) => frame.stepId === parentStep.stepId)
-      )
-    );
-    return getWorkflowOutput(descendants, scopeDepth + 1);
-  }
-
-  // Else, return the output(s)
-  // At scopeDepth > 0, always return as array to aggregate sibling iterations
-  // At scopeDepth = 0 with a single step, return the output directly
-  if (scopeDepth === 0 && stepsToProcess.length === 1) {
-    return stepsToProcess[0].output ?? null;
-  }
-
-  const outputs = stepsToProcess
-    .map((step) => step.output)
-    .filter((output): output is JsonValue => output !== undefined);
-
-  return outputs.length > 0 ? outputs : null;
-};
-
 export const executeWorkflow = async ({
   workflowId,
   workflowParams,

…_types/workflow/execute_workflow.test.ts …pes/workflow/get_workflow_output.test.tsx-pack/platform/plugins/shared/onechat/server/services/tools/tool_types/workflow/execute_workflow.test.ts renamed to x-pack/platform/plugins/shared/onechat/server/services/tools/tool_types/workflow/get_workflow_output.test.ts x-pack/platform/plugins/shared/onechat/server/services/tools/tool_types/workflow/execute_workflow.test.ts renamed to x-pack/platform/plugins/shared/onechat/server/services/tools/tool_types/workflow/get_workflow_output.test.ts

@@ -5,7 +5,7 @@
  * 2.0.
  */
 
-import { getWorkflowOutput } from './execute_workflow';
+import { getWorkflowOutput } from './get_workflow_output';
 import type { WorkflowStepExecutionDto } from '@kbn/workflows/types/v1';
 import { ExecutionStatus } from '@kbn/workflows/types/v1';
 
@@ -36,6 +36,17 @@ describe('getWorkflowOutput', () => {
       const result = getWorkflowOutput(steps);
       expect(result).toBeNull();
     });
+
+    it('should handle non-empty initial stack', () => {
+      const steps: WorkflowStepExecutionDto[] = [
+        createStep('step1', { result: 'first' }, [{ stepId: 'top-wrapper' }]),
+        createStep('step2', { result: 'second' }, [{ stepId: 'top-wrapper' }]),
+        createStep('step3', { result: 'third' }, [{ stepId: 'top-wrapper' }]),
+      ];
+
+      const result = getWorkflowOutput(steps);
+      expect(result).toEqual({ result: 'third' });
+    });
   });
 
   describe('foreach loops', () => {

x-pack/platform/plugins/shared/onechat/server/services/tools/tool_types/workflow/get_workflow_output.ts

@@ -0,0 +1,81 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import type { WorkflowStepExecutionDto } from '@kbn/workflows/types/v1';
+import type { JsonValue } from '@kbn/utility-types';
+
+/**
+ * Recursively extracts the output from a workflow execution's step executions.
+ * At top-level (scopeDepth=0), finds the last step. At nested levels (scopeDepth>0),
+ * considers all steps at that level. If steps have children, recurses into them.
+ * Otherwise, returns their output(s).
+ */
+export const getWorkflowOutput = (stepExecutions: WorkflowStepExecutionDto[]): JsonValue => {
+  if (stepExecutions.length === 0) {
+    return null;
+  }
+
+  // workflow execution do not necessarily start at depth 0
+  let minDepth = stepExecutions[0].scopeStack.length;
+  for (let i = 1; i < stepExecutions.length; i++) {
+    minDepth = Math.min(minDepth, stepExecutions[i].scopeStack.length);
+  }
+
+  return getWorkflowOutputRecursive(stepExecutions, minDepth, minDepth);
+};
+
+const getWorkflowOutputRecursive = (
+  stepExecutions: WorkflowStepExecutionDto[],
+  scopeDepth: number,
+  minDepth: number
+): JsonValue => {
+  if (stepExecutions.length === 0) {
+    return null;
+  }
+
+  // Filter for steps at the current scope depth
+  const stepsAtThisLevel = stepExecutions.filter((step) => step.scopeStack.length === scopeDepth);
+  if (stepsAtThisLevel.length === 0) {
+    return null;
+  }
+
+  // At top-level (scopeDepth = minDepth), only consider the last step
+  // At nested levels (scopeDepth > minDepth), consider all steps
+  const stepsToProcess =
+    scopeDepth === minDepth ? [stepsAtThisLevel[stepsAtThisLevel.length - 1]] : stepsAtThisLevel;
+
+  // Find all children of the steps we're processing
+  const children = stepExecutions.filter((step) => {
+    if (step.scopeStack.length !== scopeDepth + 1) return false;
+    const lastFrame = step.scopeStack[step.scopeStack.length - 1];
+    return stepsToProcess.some((parentStep) => lastFrame.stepId === parentStep.stepId);
+  });
+
+  // If there are children, recurse into them
+  // Pass only descendants (steps that have any of stepsToProcess in their scopeStack)
+  if (children.length > 0) {
+    const descendants = stepExecutions.filter((step) =>
+      step.scopeStack.some((frame) =>
+        stepsToProcess.some((parentStep) => frame.stepId === parentStep.stepId)
+      )
+    );
+    return getWorkflowOutputRecursive(descendants, scopeDepth + 1, minDepth);
+  }
+
+  // Else, return the output(s)
+  // At scopeDepth > minDepth, always return as array to aggregate sibling iterations
+  // At scopeDepth = minDepth with a single step, return the output directly
+  if (scopeDepth === minDepth && stepsToProcess.length === 1) {
+    return stepsToProcess[0].output ?? null;
+  }
+
+  const outputs = stepsToProcess
+    .map((step) => step.output)
+    .filter((output): output is JsonValue => output !== undefined);
+
+  return outputs.length > 0 ? outputs : null;
+};