Editor: guard against non-string values in style engine.

Checks that the value passed to add_declaration is a string to prevent fatal errors due to malformed block attributes.

Props andrewserong.
Fixes #64545.


git-svn-id: https://develop.svn.wordpress.org/trunk@61516 602fd350-edb4-49c9-b593-d223f7449a82

Author: tellthemachines

src/wp-includes/style-engine/class-wp-style-engine-css-declarations.php

@@ -59,6 +59,11 @@ public function add_declaration( $property, $value ) {
 			return $this;
 		}
 
+		// Bail early if value is not a string. Prevents fatal errors from malformed block markup.
+		if ( ! is_string( $value ) ) {
+			return $this;
+		}
+
 		// Trims the value. If empty, bail early.
 		$value = trim( $value );
 		if ( '' === $value ) {

tests/phpunit/tests/style-engine/wpStyleEngineCssDeclarations.php

@@ -290,4 +290,32 @@ public function test_should_remove_multiple_declarations() {
 			'Output after removing "color" and "margin" declarations via `remove_declarations()` does not match expectations'
 		);
 	}
+
+	/**
+	 * Tests that non-string values are rejected without causing fatal errors.
+	 *
+	 * @ticket 64545
+	 *
+	 * @covers ::add_declaration
+	 */
+	public function test_should_reject_non_string_values() {
+		$css_declarations = new WP_Style_Engine_CSS_Declarations();
+
+		// Add valid string value first.
+		$css_declarations->add_declaration( 'color', 'red' );
+
+		// Try to add array value - should be silently rejected.
+		$css_declarations->add_declaration( 'padding-margin', array( 'top' => '10px' ) );
+
+		// Try to add other non-string values.
+		$css_declarations->add_declaration( 'font-size', 123 );
+		$css_declarations->add_declaration( 'margin', null );
+
+		// Only the valid string value should be stored.
+		$this->assertSame(
+			array( 'color' => 'red' ),
+			$css_declarations->get_declarations(),
+			'Non-string values should be rejected without causing errors.'
+		);
+	}
 }