From e6d7af33fa6c48aa4d7707bcbd833f2846323b8a Mon Sep 17 00:00:00 2001
From: Claude <claude@anthropic.com>
Date: Thu, 25 Jun 2026 00:23:02 -0400
Subject: [PATCH] test(ui): deepen keyed reconciliation (complex moves)
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Toward React equivalency for the reconciler's hardest move patterns: full reverse
(order flips, every node moved not recreated — identity preserved), simultaneous
insert+remove, collapse to one survivor, and grow back. Each produces the correct
order and child count.

Verified via the native reconciler harness (the same surface that found the
v3.4.8 duplicate-key leak). All pass; no version bump.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 ui/reconciler_keyed_moves_test.go | 88 +++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 ui/reconciler_keyed_moves_test.go

diff --git a/ui/reconciler_keyed_moves_test.go b/ui/reconciler_keyed_moves_test.go
new file mode 100644
index 00000000..6c9b2356
--- /dev/null
+++ b/ui/reconciler_keyed_moves_test.go
@@ -0,0 +1,88 @@
+//go:build !js || !wasm
+
+package ui_test
+
+import (
+	"testing"
+
+	"github.com/monstercameron/GoWebComponents/internal/platform/mockdom"
+	"github.com/monstercameron/GoWebComponents/internal/runtime"
+)
+
+func keyedListWithData(parseKeys ...string) *runtime.Element {
+	parseKids := make([]any, len(parseKeys))
+	for parseI, parseK := range parseKeys {
+		parseKids[parseI] = runtime.CreateElement("li", map[string]any{"key": parseK, "data-k": parseK}, parseK)
+	}
+	return runtime.CreateElement("ul", map[string]any{}, parseKids...)
+}
+
+// Deepens keyed-reconciliation coverage with the harder move patterns React's
+// reconciler tests exercise: full reverse (identity preserved), simultaneous
+// insert+remove, and collapse — each producing the correct order and child count.
+func TestKeyedComplexMoves(t *testing.T) {
+	adapter := mockdom.NewMockDOMAdapter()
+	rt := runtime.NewRuntime(runtime.Config{DOMAdapter: adapter, Reset: true})
+	root := adapter.CreateElement("div")
+
+	order := func() []string {
+		parseUL := adapter.GetChildren(root)[0]
+		var parseOut []string
+		for _, parseLI := range adapter.GetChildren(parseUL) {
+			if parseN, parseOk := parseLI.(*mockdom.MockDOMNode); parseOk {
+				parseOut = append(parseOut, parseN.Attrs["data-k"])
+			}
+		}
+		return parseOut
+	}
+	idOfKey := func(parseKey string) int {
+		parseUL := adapter.GetChildren(root)[0]
+		for _, parseLI := range adapter.GetChildren(parseUL) {
+			if parseN, parseOk := parseLI.(*mockdom.MockDOMNode); parseOk && parseN.Attrs["data-k"] == parseKey {
+				return parseN.ID
+			}
+		}
+		return -1
+	}
+	equal := func(parseGot, parseWant []string) bool {
+		if len(parseGot) != len(parseWant) {
+			return false
+		}
+		for parseI := range parseGot {
+			if parseGot[parseI] != parseWant[parseI] {
+				return false
+			}
+		}
+		return true
+	}
+
+	rt.RenderInto(root, keyedListWithData("a", "b", "c", "d", "e"))
+	parseIDA, parseIDE := idOfKey("a"), idOfKey("e")
+
+	// Full reverse: order flips, every node is moved (not recreated).
+	rt.RenderInto(root, keyedListWithData("e", "d", "c", "b", "a"))
+	if !equal(order(), []string{"e", "d", "c", "b", "a"}) {
+		t.Fatalf("reverse order = %v", order())
+	}
+	if idOfKey("a") != parseIDA || idOfKey("e") != parseIDE {
+		t.Errorf("reverse recreated nodes (a: %d->%d, e: %d->%d)", parseIDA, idOfKey("a"), parseIDE, idOfKey("e"))
+	}
+
+	// Simultaneous insert (x, y) and remove (b, d).
+	rt.RenderInto(root, keyedListWithData("e", "x", "c", "y", "a"))
+	if !equal(order(), []string{"e", "x", "c", "y", "a"}) {
+		t.Errorf("insert+remove order = %v, want [e x c y a]", order())
+	}
+
+	// Collapse to a single survivor.
+	rt.RenderInto(root, keyedListWithData("c"))
+	if !equal(order(), []string{"c"}) {
+		t.Errorf("collapse order = %v, want [c]", order())
+	}
+
+	// Grow back from one.
+	rt.RenderInto(root, keyedListWithData("c", "z", "w"))
+	if !equal(order(), []string{"c", "z", "w"}) {
+		t.Errorf("grow order = %v, want [c z w]", order())
+	}
+}