Introduce a _deprecated_class() function.

Similar to other function in the `_deprecated_*` series, `_deprecated_class()` comes with two new hooks: `deprecated_class_run` and `deprecated_class_trigger_error`.

Support has also been added for setting class deprecation expectations in tests.

Props jrf, wvega, ohryan.
See #41125.


git-svn-id: https://develop.svn.wordpress.org/trunk@56467 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/functions.php

@@ -5595,6 +5595,64 @@ function _deprecated_constructor( $class_name, $version, $parent_class = '' ) {
 
 }
 
+/**
+ * Marks a class as deprecated and informs when it has been used.
+ *
+ * There is a {@see 'deprecated_class_run'} hook that will be called that can be used
+ * to get the backtrace up to what file and function called the
+ * deprecated class.
+ *
+ * The current behavior is to trigger a user error if `WP_DEBUG` is true.
+ *
+ * This function is to be used in the class constructor for every deprecated class.
+ * See {@see _deprecated_constructor()} for deprecating PHP4 style constructors.
+ *
+ * @since 6.4.0
+ *
+ * @param string $class       The class being instantiated
+ * @param string $version     The version of WordPress that deprecated the class.
+ * @param string $replacement Optional. The class or function that should have been called.
+ *                            Default empty string.
+ */
+function _deprecated_class( $class, $version, $replacement = '' ) {
+
+	/**
+	 * Fires when a deprecated class is called.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param string $class       The class being instantiated
+	 * @param string $replacement The class or function that should have been called.
+	 * @param string $version     The version of WordPress that deprecated the class.
+	 */
+	do_action( 'deprecated_class_run', $class, $replacement, $version );
+
+	/**
+	 * Filters whether to trigger an error for a deprecated class.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param bool $trigger Whether to trigger an error for a deprecated class. Default true.
+	 */
+	if ( WP_DEBUG && apply_filters( 'deprecated_class_trigger_error', true ) ) {
+		if ( function_exists( '__' ) ) {
+			if ( ! is_null( $replacement ) ) {
+				/* translators: 1: PHP class name, 2: version number, 3: alternative clas or function name */
+				trigger_error( sprintf( __('Class %1$s is <strong>deprecated</strong> since version %2$s! Use %3$s instead.'), $class, $version, $replacement ), E_USER_DEPRECATED );
+			} else {
+				/* translators: 1: PHP class name, 2: version number */
+				trigger_error( sprintf( __('Class %1$s is <strong>deprecated</strong> since version %2$s with no alternative available.'), $class, $version ), E_USER_DEPRECATED );
+			}
+		} else {
+			if ( ! is_null( $replacement ) ) {
+				trigger_error( sprintf( 'Class %1$s is <strong>deprecated</strong> since version %2$s! Use %3$s instead.', $class, $version, $replacement ), E_USER_DEPRECATED );
+			} else {
+				trigger_error( sprintf( 'Class %1$s is <strong>deprecated</strong> since version %2$s with no alternative available.', $class, $version ), E_USER_DEPRECATED );
+			}
+		}
+	}
+}
+
 /**
  * Marks a file as deprecated and inform when it has been used.
  *

tests/phpunit/includes/abstract-testcase.php

@@ -568,12 +568,14 @@ public function expectDeprecated() {
 
 		add_action( 'deprecated_function_run', array( $this, 'deprecated_function_run' ), 10, 3 );
 		add_action( 'deprecated_argument_run', array( $this, 'deprecated_function_run' ), 10, 3 );
+		add_action( 'deprecated_class_run', array( $this, 'deprecated_function_run' ), 10, 3 );
 		add_action( 'deprecated_file_included', array( $this, 'deprecated_function_run' ), 10, 4 );
 		add_action( 'deprecated_hook_run', array( $this, 'deprecated_function_run' ), 10, 4 );
 		add_action( 'doing_it_wrong_run', array( $this, 'doing_it_wrong_run' ), 10, 3 );
 
 		add_action( 'deprecated_function_trigger_error', '__return_false' );
 		add_action( 'deprecated_argument_trigger_error', '__return_false' );
+		add_action( 'deprecated_class_trigger_error', '__return_false' );
 		add_action( 'deprecated_file_trigger_error', '__return_false' );
 		add_action( 'deprecated_hook_trigger_error', '__return_false' );
 		add_action( 'doing_it_wrong_trigger_error', '__return_false' );
@@ -746,6 +748,23 @@ public function deprecated_function_run( $function_name, $replacement, $version,
 					}
 					break;
 
+				case 'deprecated_class_run':
+					if ( $replacement ) {
+						$message = sprintf(
+							'Class %1$s is deprecated since version %2$s! Use %3$s instead.',
+							$function_name,
+							$version,
+							$replacement
+						);
+					} else {
+						$message = sprintf(
+							'Class %1$s is deprecated since version %2$s with no alternative available.',
+							$function_name,
+							$version
+						);
+					}
+					break;
+
 				case 'deprecated_file_included':
 					if ( $replacement ) {
 						$message = sprintf(