perf(templateengine): memoise CollisionDetector's composed-module walk per check (review 2026-10-21 04/P8b)

2026-10-22 06:30:27 -04:00
parent 52aab37299
commit 0d4f7d33b9
3 changed files with 153 additions and 26 deletions
@@ -258,4 +258,55 @@ public class CollisionDetectorTests
        var collisions = CollisionDetector.DetectCollisions(a, all);
        Assert.Empty(collisions);
    }
+
+    // ========================================================================
+    // Review 2026-10-21 04/P8(b): a module reached through several slots is walked once
+    // ========================================================================
+
+    /// <summary>
+    /// Verifies that a module composed into several slots (a diamond) has its subtree
+    /// walked once per collision check — every further slot reuses the memoised member
+    /// list under its own prefix — while still producing every canonical name.
+    /// </summary>
+    [Fact]
+    public void DetectCollisions_DiamondComposition_WalksSharedModuleOnce()
+    {
+        var leaf = new Template("Leaf") { Id = 3 };
+        leaf.Attributes.Add(new TemplateAttribute("V") { Id = 30, TemplateId = 3, DataType = DataType.Float });
+
+        var mid = new Template("Mid") { Id = 2 };
+        var midCompositions = new CountingCollection<TemplateComposition>
+        {
+            new TemplateComposition("x") { Id = 20, TemplateId = 2, ComposedTemplateId = 3 },
+            new TemplateComposition("y") { Id = 21, TemplateId = 2, ComposedTemplateId = 3 },
+        };
+        mid.Compositions = midCompositions;
+
+        var root = new Template("Root") { Id = 1 };
+        root.Compositions.Add(new TemplateComposition("a") { Id = 10, TemplateId = 1, ComposedTemplateId = 2 });
+        root.Compositions.Add(new TemplateComposition("b") { Id = 11, TemplateId = 1, ComposedTemplateId = 2 });
+        root.Compositions.Add(new TemplateComposition("c") { Id = 12, TemplateId = 1, ComposedTemplateId = 2 });
+        // A genuine collision reachable only through the third slot of the shared module.
+        root.Attributes.Add(new TemplateAttribute("c.y.V") { Id = 40, TemplateId = 1, DataType = DataType.Float });
+
+        midCompositions.Enumerations = 0;
+        var collisions = CollisionDetector.DetectCollisions(root, new List<Template> { root, mid, leaf });
+
+        Assert.Equal(1, midCompositions.Enumerations); // pre-fix: 3 (once per slot)
+        var collision = Assert.Single(collisions);
+        Assert.Contains("'c.y.V'", collision);
+        Assert.Contains("module 'c.y'", collision);
+    }
+
+    /// <summary>An <see cref="ICollection{T}"/> that counts how often it is enumerated.</summary>
+    private sealed class CountingCollection<T> : List<T>, ICollection<T>
+    {
+        public int Enumerations { get; set; }
+
+        IEnumerator<T> IEnumerable<T>.GetEnumerator()
+        {
+            Enumerations++;
+            return GetEnumerator();
+        }
+    }
 }