From acd6c7a6e7b32e724e2d8c1ce1cdf52aa3851df0 Mon Sep 17 00:00:00 2001
From: Ishita Jagtap <143935560+ishitaj34@users.noreply.github.com>
Date: Fri, 16 Oct 2026 18:59:58 +0530
Subject: [PATCH] fix: strip null values from theme.json output

---
 includes/create-theme/resolver_additions.php | 27 ++++++++++
 tests/test-theme-utils.php                   | 55 ++++++++++++++++++++
 2 files changed, 82 insertions(+)

diff --git a/includes/create-theme/resolver_additions.php b/includes/create-theme/resolver_additions.php
index 3de2cc25..549d7b87 100644
--- a/includes/create-theme/resolver_additions.php
+++ b/includes/create-theme/resolver_additions.php
@@ -116,13 +116,40 @@ public static function get_user_data() {
 				: parent::get_user_data();
 		}
 
+		/**
+		 * Recursively remove null values from an array.
+		 *
+		 * The theme.json schema rejects null values and WordPress ignores them.
+		 * Empty arrays and non-null falsy values (false, 0, '') are preserved.
+		 *
+		 * @param mixed $data Data to filter.
+		 * @return mixed Data without null values.
+		 */
+		public static function strip_null_values( $data ) {
+			if ( ! is_array( $data ) ) {
+				return $data;
+			}
+
+			$clean = array();
+			foreach ( $data as $key => $value ) {
+				if ( null === $value ) {
+					continue;
+				}
+				$clean[ $key ] = self::strip_null_values( $value );
+			}
+
+			return $clean;
+		}
+
 		/**
 		 * Stringify the array data.
 		 *
 		 * $data is an array of data to be converted to a JSON string.
+		 * Null values are stripped since they are invalid in theme.json.
 		 * @return string JSON string.
 		 */
 		public static function stringify( $data ) {
+			$data = self::strip_null_values( $data );
 			$data = wp_json_encode( $data, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE );
 			// Convert spaces to tabs
 			return preg_replace( '~(?:^|\G)\h{4}~m', "\t", $data );
diff --git a/tests/test-theme-utils.php b/tests/test-theme-utils.php
index 05ab7e7f..31aa69eb 100644
--- a/tests/test-theme-utils.php
+++ b/tests/test-theme-utils.php
@@ -61,4 +61,59 @@ function oldslug_support() {
 		$this->assertStringContainsString( 'function new_slug_support', $updated_code_string );
 		$this->assertStringContainsString( "function_exists( 'new_slug_support' )", $updated_code_string );
 	}
+
+	public function test_stringify_strips_null_values() {
+		$data = array(
+			'version' => 3,
+			'styles'  => array(
+				'blocks' => array(
+					'core/quote' => array(
+						'border' => array(
+							'color' => null,
+							'style' => null,
+							'width' => null,
+							'left'  => array(
+								'color' => 'currentColor',
+								'style' => 'solid',
+								'width' => '4px',
+							),
+						),
+					),
+				),
+			),
+		);
+
+		$decoded = json_decode( CBT_Theme_JSON_Resolver::stringify( $data ), true );
+		$this->assertSame(
+			array(
+				'left' => array(
+					'color' => 'currentColor',
+					'style' => 'solid',
+					'width' => '4px',
+				),
+			),
+			$decoded['styles']['blocks']['core/quote']['border']
+		);
+		$this->assertStringNotContainsString( 'null', CBT_Theme_JSON_Resolver::stringify( $data ) );
+	}
+
+	public function test_strip_null_values_preserves_falsy_values() {
+		$data = array(
+			'custom' => false,
+			'zero'   => 0,
+			'empty'  => '',
+			'list'   => array(),
+			'none'   => null,
+		);
+
+		$this->assertSame(
+			array(
+				'custom' => false,
+				'zero'   => 0,
+				'empty'  => '',
+				'list'   => array(),
+			),
+			CBT_Theme_JSON_Resolver::strip_null_values( $data )
+		);
+	}
 }