From 0aa4d3646df3ba4c69fdc9c573b026c51060582b Mon Sep 17 00:00:00 2001
From: Ben Bowler <ben@benbowler.com>
Date: Mon, 4 Aug 2025 11:52:03 +0100
Subject: [PATCH 1/2] Remove console ignore in E2E block editor by polyfilling
 findLastIndex.

---
 assets/js/googlesitekit-polyfills.js | 30 ++++++++++++++++++++++++++++
 tests/e2e/config/bootstrap.js        |  6 ------
 2 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/assets/js/googlesitekit-polyfills.js b/assets/js/googlesitekit-polyfills.js
index 9e20970a4a7..247b349ce1b 100644
--- a/assets/js/googlesitekit-polyfills.js
+++ b/assets/js/googlesitekit-polyfills.js
@@ -20,6 +20,36 @@
 __webpack_public_path__ = `${ global._googlesitekitBaseData.assetsURL }js/`;
 
 async function loadPolyfills() {
+	// Add findLastIndex polyfill to prevent:
+	// `block-editor.js wp.blockEditor.transformStyles Failed to transform CSS.
+	// TypeError: tokenized.findLastIndex is not a function`
+	// errors blocks within Gutenberg built with node < v18.
+	if ( ! Array.prototype.findLastIndex ) {
+		Array.prototype.findLastIndex = function ( predicate, thisArg ) {
+			if ( this === null || this === undefined ) {
+				throw new TypeError(
+					'Array.prototype.findLastIndex called on null or undefined'
+				);
+			}
+			if ( typeof predicate !== 'function' ) {
+				throw new TypeError( 'predicate must be a function' );
+			}
+
+			const obj = Object( this );
+			const len = parseInt( obj.length ) || 0;
+
+			for ( let i = len - 1; i >= 0; i-- ) {
+				if ( i in obj ) {
+					const element = obj[ i ];
+					if ( predicate.call( thisArg, element, i, obj ) ) {
+						return i;
+					}
+				}
+			}
+			return -1;
+		};
+	}
+
 	if ( typeof global.IntersectionObserver === 'undefined' ) {
 		await import( 'intersection-observer' );
 	}
diff --git a/tests/e2e/config/bootstrap.js b/tests/e2e/config/bootstrap.js
index 0d8968941b6..bc762419592 100644
--- a/tests/e2e/config/bootstrap.js
+++ b/tests/e2e/config/bootstrap.js
@@ -172,12 +172,6 @@ const IGNORE_CONSOLE_MESSAGES = [
 		matcher: 'startsWith',
 		pattern: 'Warning: You are importing createRoot from',
 	},
-	// Gutenberg blockEditor.transformStyles warnings within the block editor.
-	{
-		matcher: 'includes',
-		pattern:
-			'wp.blockEditor.transformStyles Failed to transform CSS. JSHandle@error',
-	},
 ];
 
 /**

From c40706df9661996863f09b587b0f7fbb93ff2baf Mon Sep 17 00:00:00 2001
From: Ben Bowler <ben@benbowler.com>
Date: Wed, 13 Aug 2025 14:22:29 +0100
Subject: [PATCH 2/2] Ad debug logging where findLastIndex polyfill is
 required.

---
 assets/js/googlesitekit-polyfills.js | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/assets/js/googlesitekit-polyfills.js b/assets/js/googlesitekit-polyfills.js
index 247b349ce1b..1b84c97ef39 100644
--- a/assets/js/googlesitekit-polyfills.js
+++ b/assets/js/googlesitekit-polyfills.js
@@ -26,6 +26,13 @@ async function loadPolyfills() {
 	// errors blocks within Gutenberg built with node < v18.
 	if ( ! Array.prototype.findLastIndex ) {
 		Array.prototype.findLastIndex = function ( predicate, thisArg ) {
+			// eslint-disable-next-line no-console
+			console.error(
+				'Array.prototype.findLastIndex polyfill applied to:',
+				this,
+				new Error().stack
+			);
+
 			if ( this === null || this === undefined ) {
 				throw new TypeError(
 					'Array.prototype.findLastIndex called on null or undefined'