From 40c610acb3016d2e1253e0434e86e32b672f4ec8 Mon Sep 17 00:00:00 2001
From: OpaqueRock <305760598+OpaqueRock@users.noreply.github.com>
Date: Wed, 22 Jul 2026 17:26:30 +0300
Subject: [PATCH] Fix undefined-array-key warning in visit() for custom Node
 kinds

Node::kind is not required to be a NodeKind constant (custom Node
subclasses are supported), so $visitorKeys[$node->kind] can be
undefined. Previously the ?? [] fallback was applied to the whole
ternary result, so it never triggered for the $inList branch and left
the non-list branch's array access unguarded. Move the fallback onto
just that array access instead.

Add regression tests covering generic and kind-specific visitors for
a custom Node kind.
---
 src/Language/Visitor.php       |  4 ++-
 tests/Language/VisitorTest.php | 66 ++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+), 1 deletion(-)

diff --git a/src/Language/Visitor.php b/src/Language/Visitor.php
index d1101c68a..c63f45da2 100644
--- a/src/Language/Visitor.php
+++ b/src/Language/Visitor.php
@@ -319,7 +319,9 @@ public static function visit(object $root, array $visitor, ?array $keyMap = null
                 ];
                 $inList = $node instanceof NodeList;
 
-                $keys = ($inList ? $node : $visitorKeys[$node->kind]) ?? [];
+                // Nodes with a kind not present in $visitorKeys (e.g. a custom
+                // Node subclass) are treated as leaves, i.e. no children.
+                $keys = $inList ? $node : ($visitorKeys[$node->kind] ?? []);
                 $index = -1;
                 $edits = [];
                 if ($parent !== null) {
diff --git a/tests/Language/VisitorTest.php b/tests/Language/VisitorTest.php
index 12acd43e0..70788a281 100644
--- a/tests/Language/VisitorTest.php
+++ b/tests/Language/VisitorTest.php
@@ -1905,4 +1905,70 @@ public function testThrowsExceptionWhenAddingIntegerToNodeList(): void
             ]
         );
     }
+
+    /**
+     * visit() must correctly invoke generic enter/leave visitors for a Node
+     * whose kind is not one of the built-in NodeKind constants (e.g. a
+     * custom Node subclass defined by a consumer).
+     */
+    public function testVisitCallsGenericVisitorsForCustomKind(): void
+    {
+        $customNode = new class([]) extends Node {
+            public string $kind = 'CustomKind';
+        };
+
+        $visited = [];
+
+        Visitor::visit(
+            $customNode,
+            [
+                'enter' => static function (Node $node) use (&$visited): void {
+                    $visited[] = ['enter', $node->kind];
+                },
+                'leave' => static function (Node $node) use (&$visited): void {
+                    $visited[] = ['leave', $node->kind];
+                },
+            ]
+        );
+
+        self::assertSame(
+            [
+                ['enter', 'CustomKind'],
+                ['leave', 'CustomKind'],
+            ],
+            $visited
+        );
+    }
+
+    /** Same as testVisitCallsGenericVisitorsForCustomKind, but for a visitor keyed specifically by the custom kind. */
+    public function testVisitCallsKindSpecificVisitorForCustomKind(): void
+    {
+        $customNode = new class([]) extends Node {
+            public string $kind = 'CustomKind';
+        };
+
+        $visited = [];
+
+        Visitor::visit(
+            $customNode,
+            [
+                'CustomKind' => [
+                    'enter' => static function (Node $node) use (&$visited): void {
+                        $visited[] = ['enter', $node->kind];
+                    },
+                    'leave' => static function (Node $node) use (&$visited): void {
+                        $visited[] = ['leave', $node->kind];
+                    },
+                ],
+            ]
+        );
+
+        self::assertSame(
+            [
+                ['enter', 'CustomKind'],
+                ['leave', 'CustomKind'],
+            ],
+            $visited
+        );
+    }
 }