From 780e2bc436ccdee9221a9ae5e37490989bee57ed Mon Sep 17 00:00:00 2001
From: Aaron Robertshaw <60436221+aaronrobertshaw@users.noreply.github.com>
Date: Wed, 24 Jun 2026 16:21:45 -0700
Subject: [PATCH 1/2] Editor: Guard elements hover styles against a missing
 hover selector.

Only render `:hover` element styles for element types that actually define a
hover selector. In `wp_render_elements_support_styles()`, only the `link`
element type defines a `hover_selector`. If a block's `style.elements` carries
a `:hover` object for `button` or `heading`, accessing
`$element_config['hover_selector']` reaches for a key that does not exist,
emitting an "Undefined array key 'hover_selector'" warning and passing an
empty selector to the style engine.

Add a `! empty( $element_config['hover_selector'] )` guard so hover processing
is skipped for element types without a hover selector, and extend the elements
styles test with a `button` `:hover` case that confirms only the base rule is
emitted.

Backport of Gutenberg PR https://github.com/WordPress/gutenberg/pull/79511.

Props aaronrobertshaw.
See #65538.
---
 .../wpRenderElementsSupportStyles.php            | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/tests/phpunit/tests/block-supports/wpRenderElementsSupportStyles.php b/tests/phpunit/tests/block-supports/wpRenderElementsSupportStyles.php
index 5c9fc8af5819d..7500c1d3f6f5e 100644
--- a/tests/phpunit/tests/block-supports/wpRenderElementsSupportStyles.php
+++ b/tests/phpunit/tests/block-supports/wpRenderElementsSupportStyles.php
@@ -22,6 +22,7 @@ public function tear_down() {
 	 *
 	 * @ticket 59555
 	 * @ticket 60557
+	 * @ticket 65538
 	 *
 	 * @covers ::wp_render_elements_support_styles
 	 *
@@ -185,6 +186,21 @@ public function data_elements_block_support_styles() {
 				),
 				'expected_styles' => '/^.wp-elements-\d+ .wp-element-button, .wp-elements-\d+ .wp-block-button__link' . $color_css_rules . '$/',
 			),
+			'button hover styles are skipped without a hover selector' => array(
+				'color_settings'  => array( 'button' => true ),
+				'elements_styles' => array(
+					'button' => array(
+						'color'  => $color_styles,
+						':hover' => array( 'color' => $color_styles ),
+					),
+				),
+				/*
+				 * Only the base button rule should be emitted. The button element
+				 * type has no `hover_selector`, so the `:hover` object must be
+				 * ignored rather than triggering an undefined array key warning.
+				 */
+				'expected_styles' => '/^.wp-elements-[a-f0-9]{32} .wp-element-button, .wp-elements-[a-f0-9]{32} .wp-block-button__link' . $color_css_rules . '$/',
+			),
 			'link element styles are applied'            => array(
 				'color_settings'  => array( 'link' => true ),
 				'elements_styles' => array(

From f4605cc9b7ed6bc88e06047d40fbbdc15576667b Mon Sep 17 00:00:00 2001
From: Aaron Robertshaw <60436221+aaronrobertshaw@users.noreply.github.com>
Date: Thu, 25 Jun 2026 13:36:34 -0700
Subject: [PATCH 2/2] Correct test regex for recent change to element classname
 generation

---
 .../tests/block-supports/wpRenderElementsSupportStyles.php     | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tests/phpunit/tests/block-supports/wpRenderElementsSupportStyles.php b/tests/phpunit/tests/block-supports/wpRenderElementsSupportStyles.php
index 7500c1d3f6f5e..386d2a0041159 100644
--- a/tests/phpunit/tests/block-supports/wpRenderElementsSupportStyles.php
+++ b/tests/phpunit/tests/block-supports/wpRenderElementsSupportStyles.php
@@ -194,12 +194,13 @@ public function data_elements_block_support_styles() {
 						':hover' => array( 'color' => $color_styles ),
 					),
 				),
+
 				/*
 				 * Only the base button rule should be emitted. The button element
 				 * type has no `hover_selector`, so the `:hover` object must be
 				 * ignored rather than triggering an undefined array key warning.
 				 */
-				'expected_styles' => '/^.wp-elements-[a-f0-9]{32} .wp-element-button, .wp-elements-[a-f0-9]{32} .wp-block-button__link' . $color_css_rules . '$/',
+				'expected_styles' => '/^.wp-elements-\d+ .wp-element-button, .wp-elements-\d+ .wp-block-button__link' . $color_css_rules . '$/',
 			),
 			'link element styles are applied'            => array(
 				'color_settings'  => array( 'link' => true ),