Ensure stylesheets of zero size can be inlined

Author: westonruter

src/wp-includes/script-loader.php

@@ -3081,7 +3081,7 @@ function wp_maybe_inline_styles() {
 		$path = $wp_styles->get_data( $handle, 'path' );
 		if ( $path && $src ) {
 			$size = wp_filesize( $path );
-			if ( 0 === $size ) {
+			if ( 0 === $size && ! file_exists( $path ) ) {
 				_doing_it_wrong(
 					__FUNCTION__,
 					sprintf(

tests/phpunit/tests/dependencies/styles.php

@@ -794,11 +794,13 @@ public function test_wp_maybe_inline_styles_bad_path_at_file_size_check() {
 	 * @expectedIncorrectUsage wp_maybe_inline_styles
 	 */
 	public function test_wp_maybe_inline_styles_bad_path_with_file_size_provided() {
+		$inc_path = '/css/ancient-themes.css'; // Does not exist.
+
 		// This ensures the initial file size check is bypassed.
 		add_filter(
 			'pre_wp_filesize',
-			static function ( $size, $path ) {
-				if ( str_contains( $path, 'ancient-themes.css' ) ) {
+			static function ( $size, $path ) use ( $inc_path ) {
+				if ( str_contains( $path, $inc_path ) ) {
 					$size = 1000;
 				}
 				return $size;
@@ -807,9 +809,8 @@ static function ( $size, $path ) {
 			2
 		);
 
-		$handle   = 'test-handle';
-		$inc_path = '/css/ancient-themes.css'; // Does not exist.
-		$url      = '/' . WPINC . $inc_path;
+		$handle = 'test-handle';
+		$url    = '/' . WPINC . $inc_path;
 		wp_register_style( $handle, $url );
 		wp_style_add_data( $handle, 'path', ABSPATH . WPINC . $inc_path );
 		wp_enqueue_style( $handle );
@@ -819,6 +820,37 @@ static function ( $size, $path ) {
 		$this->assertSame( $GLOBALS['wp_styles']->registered[ $handle ]->src, $url );
 	}
 
+	/**
+	 * @ticket 64447
+	 *
+	 * @covers ::wp_maybe_inline_styles
+	 */
+	public function test_wp_maybe_inline_styles_good_path_with_zero_file_size_provided() {
+		$inc_path = '/css/classic-themes.css';
+
+		// This simulates the file having a zero size.
+		add_filter(
+			'pre_wp_filesize',
+			static function ( $size, $path ) use ( $inc_path ) {
+				if ( str_contains( $path, $inc_path ) ) {
+					$size = 0;
+				}
+				return $size;
+			},
+			10,
+			2
+		);
+
+		$handle = 'test-handle';
+		wp_register_style( $handle, '/' . WPINC . $inc_path );
+		wp_style_add_data( $handle, 'path', ABSPATH . WPINC . $inc_path );
+		wp_enqueue_style( $handle );
+
+		wp_maybe_inline_styles();
+
+		$this->assertFalse( $GLOBALS['wp_styles']->registered[ $handle ]->src );
+	}
+
 	/**
 	 * @ticket 63887
 	 */