Give a warning when flushing cache on multisite with --url=<url> (#86)

* When flushing cache on a multisite give a warning.

Cache flushes on all sites, not just the current url.

* Updated the --url warning.

* Remove comma from the message

---------

Co-authored-by: Daniel Bachhuber <[email protected]>

Author: janw-me

features/cache.feature

@@ -132,3 +132,18 @@ Feature: Managed the WordPress object cache
       """
       Error: Could not replace object 'bar' in group 'foo'. Does it not exist?
       """
+
+  Scenario: Flushing cache on a multisite installation
+    Given a WP multisite installation
+
+    When I try `wp cache flush`
+    Then STDERR should not contain:
+      """
+      Warning: Ignoring the --url=<url> argument because flushing the cache affects all sites on a multisite installation.
+      """
+
+    When I try `wp cache flush --url=example.com`
+    Then STDERR should contain:
+      """
+      Warning: Ignoring the --url=<url> argument because flushing the cache affects all sites on a multisite installation.
+      """

src/Cache_Command.php

@@ -155,8 +155,12 @@ public function delete( $args, $assoc_args ) {
 	 *     Success: The cache was flushed.
 	 */
 	public function flush( $args, $assoc_args ) {
-		$value = wp_cache_flush();
 
+		if ( WP_CLI::has_config( 'url' ) && ! empty( WP_CLI::get_config()['url'] ) && is_multisite() ) {
+			WP_CLI::warning( 'Ignoring the --url=<url> argument because flushing the cache affects all sites on a multisite installation.' );
+		}
+
+		$value = wp_cache_flush();
 		if ( false === $value ) {
 			WP_CLI::error( 'The object cache could not be flushed.' );
 		}