Respect doing_cron transient in wp cron event run --due-now

features/cron-event.feature

@@ -244,3 +244,31 @@ Feature: Manage WP Cron events
       """
       Debug: Beginning execution of cron event 'wp_version_check'
       """
+
+  Scenario: --due-now respects the doing_cron transient and skips when another run is in progress
+    When I run `wp cron event schedule wp_cli_test_event_lock now hourly`
+    Then STDOUT should contain:
+      """
+      Success: Scheduled event with hook 'wp_cli_test_event_lock'
+      """
+
+    # Simulate an in-progress cron run by setting the doing_cron transient.
+    When I run `wp eval 'set_transient( "doing_cron", sprintf( "%.22F", microtime( true ) ) );'`
+
+    And I try `wp cron event run --due-now`
+    Then STDERR should contain:
+      """
+      Warning: A cron event run is already in progress; skipping.
+      """
+    And STDOUT should not contain:
+      """
+      wp_cli_test_event_lock
+      """
+
+    # After the transient is cleared, the run should proceed normally.
+    When I run `wp eval 'delete_transient( "doing_cron" );'`
+    And I try `wp cron event run --due-now`
+    Then STDOUT should contain:
+      """
+      Executed the cron event 'wp_cli_test_event_lock'
+      """

features/cron.feature

@@ -307,8 +307,13 @@ Feature: Manage WP-Cron events and schedules
   # executes the "wp_privacy_delete_old_export_files" event there.
   @require-wp-5.0
   Scenario: Run currently scheduled events
+    # Disable web-triggered cron so spawn_cron() cannot set doing_cron between
+    # steps - wp cron event run always defines DOING_CRON so this has no effect
+    # on the commands being tested.
+    When I run `wp config set DISABLE_WP_CRON true --raw`
+
     # WP throws a notice here for older versions of core.
-    When I try `wp cron event run --all`
+    And I try `wp cron event run --all`
     Then STDOUT should contain:
       """
       Executed the cron event 'wp_version_check'

src/Cron_Event_Command.php

@@ -226,7 +226,8 @@ public function schedule( $args, $assoc_args ) {
 	 * : One or more hooks to run.
 	 *
 	 * [--due-now]
-	 * : Run all hooks due right now.
+	 * : Run all hooks due right now. Respects the doing_cron transient to
+	 * prevent overlapping runs.
 	 *
 	 * [--exclude=<hooks>]
 	 * : Comma-separated list of hooks to exclude.
@@ -243,10 +244,27 @@ public function schedule( $args, $assoc_args ) {
 	 *     Success: Executed a total of 2 cron events.
 	 */
 	public function run( $args, $assoc_args ) {
+		$due_now = Utils\get_flag_value( $assoc_args, 'due-now' );
+
+		$doing_cron_value = null;
+
+		if ( $due_now ) {
+			$lock_timeout         = defined( 'WP_CRON_LOCK_TIMEOUT' ) ? WP_CRON_LOCK_TIMEOUT : 60;
+			$doing_cron_transient = get_transient( 'doing_cron' );
+			if ( is_numeric( $doing_cron_transient ) && (float) $doing_cron_transient > microtime( true ) - $lock_timeout ) {
+				WP_CLI::warning( 'A cron event run is already in progress; skipping.' );
+				return;
+			}
+			$doing_cron_value = sprintf( '%.22F', microtime( true ) );
+			set_transient( 'doing_cron', $doing_cron_value, $lock_timeout );
+		}
 
 		$events = self::get_selected_cron_events( $args, $assoc_args );
 
 		if ( is_wp_error( $events ) ) {
+			if ( $due_now && get_transient( 'doing_cron' ) === $doing_cron_value ) {
+				delete_transient( 'doing_cron' );
+			}
 			WP_CLI::error( $events );
 		}
 
@@ -263,6 +281,10 @@ public function run( $args, $assoc_args ) {
 			}
 		}
 
+		if ( $due_now && get_transient( 'doing_cron' ) === $doing_cron_value ) {
+			delete_transient( 'doing_cron' );
+		}
+
 		$message = ( 1 === $executed ) ? 'Executed a total of %d cron event.' : 'Executed a total of %d cron events.';
 		WP_CLI::success( sprintf( $message, $executed ) );
 	}