Fix two related bugs in the BuildWorkflowParameters component:

   1. Workflow parameters merging when changing workflow types
      When user changed from one workflow type to another (e.g., google-cloud-buildpacks
      to docker), the review step showed merged parameters from both workflows instead
      of only the currently selected workflow's parameters.

   2. Form data loss when navigating back in wizard
      When user navigated forward to trait steps and then back to workflow configuration,
      all entered parameters were lost, forcing them to re-enter values.

Author: kaviththiranga

packages/app/src/scaffolder/BuildWorkflowParameters/BuildWorkflowParametersExtension.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useState } from 'react';
+import { useEffect, useState, useRef } from 'react';
 import { FieldExtensionComponentProps } from '@backstage/plugin-scaffolder-react';
 import { Typography, Box } from '@material-ui/core';
 import {
@@ -45,6 +45,10 @@ export const BuildWorkflowParameters = ({
   const [loading, setLoading] = useState(false);
   const [error, setError] = useState<string | null>(null);
 
+  // Track workflow changes to force Form remount only when workflow actually changes
+  const [resetKey, setResetKey] = useState(0);
+  const prevWorkflowRef = useRef<string | undefined>(undefined);
+
   const discoveryApi = useApi(discoveryApiRef);
   const identityApi = useApi(identityApiRef);
 
@@ -53,6 +57,16 @@ export const BuildWorkflowParameters = ({
   const selectedWorkflowName = formContext?.formData?.workflow_name;
   const organizationName = formContext?.formData?.organization_name;
 
+  // Increment resetKey only when workflow actually changes
+  // This forces Form remount only on workflow change, not on every render
+  useEffect(() => {
+    if (prevWorkflowRef.current !== undefined &&
+        prevWorkflowRef.current !== selectedWorkflowName) {
+      setResetKey(prev => prev + 1);
+    }
+    prevWorkflowRef.current = selectedWorkflowName;
+  }, [selectedWorkflowName]);
+
   // Fetch workflow schema when workflow selection changes
   useEffect(() => {
     let ignore = false;
@@ -124,20 +138,27 @@ export const BuildWorkflowParameters = ({
     };
   }, [selectedWorkflowName, organizationName, discoveryApi, identityApi]);
 
-  // Sync schema to formData when workflow schema changes
+  // Sync schema to formData when workflow changes (not just when schema loads)
   useEffect(() => {
-    if (workflowSchema) {
-      // Update formData to include the schema for validation
+    if (workflowSchema && resetKey > 0) {
+      // Clear old parameters only when workflow actually changes (resetKey increments)
+      // This prevents clearing when user navigates back to this step
+      onChange({
+        parameters: {},
+        schema: workflowSchema,
+      });
+    } else if (workflowSchema && resetKey === 0 && !formData?.schema) {
+      // First time loading: initialize with existing or empty parameters
       onChange({
         parameters: formData?.parameters || {},
         schema: workflowSchema,
       });
     }
-    // We intentionally only depend on workflowSchema to avoid infinite loop.
+    // We intentionally only depend on workflowSchema and resetKey.
     // Adding onChange or formData would cause infinite re-renders:
     // onChange -> formData changes -> useEffect triggers -> onChange -> loop
     // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [workflowSchema]);
+  }, [workflowSchema, resetKey]);
 
   // Handle form data changes from RJSF
   const handleFormChange = (changeEvent: any) => {
@@ -190,6 +211,7 @@ export const BuildWorkflowParameters = ({
           Workflow Parameters
         </Typography>
         <Form
+          key={resetKey}
           schema={workflowSchema}
           uiSchema={uiSchema}
           formData={formData?.parameters || {}}