fix(template-engine): resolve TemplateEngine-015,016 — cascade-rename nested derived templates, correct composed-script ParentPath

src/ScadaLink.TemplateEngine/TemplateService.cs

@@ -705,12 +705,28 @@ public class TemplateService
         {
             var newDerivedName = $"{owner.Name}.{newInstanceName}";
             var allTemplates = await _repository.GetAllTemplatesAsync(cancellationToken);
-            if (allTemplates.Any(t => t.Id != derived.Id && t.Name == newDerivedName))
-                return Result<TemplateComposition>.Failure(
-                    $"Cannot rename derived template to '{newDerivedName}': a template with that name already exists.");
 
-            derived.Name = newDerivedName;
-            await _repository.UpdateTemplateAsync(derived, cancellationToken);
+            // The cascade of derived templates created by AddComposition follows a
+            // dotted path (Pump.TempSensor and the nested Pump.TempSensor.Probe1).
+            // Renaming the slot must rename every derived template in that cascade
+            // so the dotted-path naming invariant holds — pre-check every new name
+            // the cascade will introduce before any row mutates.
+            var renames = new List<(Template Template, string NewName)>();
+            await CollectCascadeRenamesAsync(derived, newDerivedName, renames, cancellationToken);
+
+            var renamedIds = renames.Select(r => r.Template.Id).ToHashSet();
+            foreach (var (_, newName) in renames)
+            {
+                if (allTemplates.Any(t => !renamedIds.Contains(t.Id) && t.Name == newName))
+                    return Result<TemplateComposition>.Failure(
+                        $"Cannot rename derived template to '{newName}': a template with that name already exists.");
+            }
+
+            foreach (var (template, newName) in renames)
+            {
+                template.Name = newName;
+                await _repository.UpdateTemplateAsync(template, cancellationToken);
+            }
         }
 
         composition.InstanceName = newInstanceName;
@@ -747,6 +763,30 @@ public class TemplateService
         return Result<bool>.Success(true);
     }
 
+    /// <summary>
+    /// Recursively collects the (template, new name) pairs for a renamed derived
+    /// template and every cascaded inner derived template beneath it. Each inner
+    /// derived's new name is re-derived from its renamed parent and the slot's
+    /// instance name (mirroring the cascade <see cref="CreateCascadedCompositionAsync"/>
+    /// builds and the recursion in <see cref="CascadeDeleteDerivedAsync"/>).
+    /// </summary>
+    private async Task CollectCascadeRenamesAsync(
+        Template derived,
+        string newName,
+        List<(Template Template, string NewName)> renames,
+        CancellationToken cancellationToken)
+    {
+        renames.Add((derived, newName));
+
+        foreach (var child in derived.Compositions.ToList())
+        {
+            var childDerived = await _repository.GetTemplateByIdAsync(child.ComposedTemplateId, cancellationToken);
+            if (childDerived != null && childDerived.IsDerived && childDerived.OwnerCompositionId == child.Id)
+                await CollectCascadeRenamesAsync(
+                    childDerived, $"{newName}.{child.InstanceName}", renames, cancellationToken);
+        }
+    }
+
     /// <summary>
     /// Recursively deletes a derived template along with the cascade of inner
     /// derived templates the compose flow created. Each composition row on the