Add wp cache supports <feature> command (#84)

* Added command: wp cache supports <feature>

* Added failsafe for older WP versions.

* Create a dedicated `Scenario` and only run for WP 6.1

* Use `When I run` for successful invocations

* Register the command and regenerate the README

---------

Co-authored-by: Daniel Bachhuber <daniel.bachhuber@automattic.com>

Author: janw-me

README.md

@@ -304,6 +304,33 @@ Errors if the value can't be set.
 
 
 
+### wp cache supports
+
+Determines whether the object cache implementation supports a particular feature.
+
+~~~
+wp cache supports <feature>
+~~~
+
+**OPTIONS**
+
+	<feature>
+		Name of the feature to check for.
+
+**EXAMPLES**
+
+    # Check whether is add_multiple supported.
+    $ wp cache supports add_multiple
+    $ echo $?
+    0
+
+    # Bash script for checking whether for support like this:
+    if ! wp cache supports non_existing; then
+        echo 'non_existing is not supported'
+    fi
+
+
+
 ### wp cache type
 
 Attempts to determine which object cache is being used.

composer.json

@@ -41,6 +41,7 @@
             "cache incr",
             "cache replace",
             "cache set",
+            "cache supports",
             "cache type",
             "transient",
             "transient delete",

features/cache.feature

@@ -147,3 +147,13 @@ Feature: Managed the WordPress object cache
       """
       Warning: Ignoring the --url=<url> argument because flushing the cache affects all sites on a multisite installation.
       """
+
+  @require-wp-6.1
+  Scenario: Checking if the cache supports a feature
+    Given a WP install
+
+    When I try `wp cache supports non_existing`
+    Then the return code should be 1
+
+    When I run `wp cache supports set_multiple`
+    Then the return code should be 0

src/Cache_Command.php

@@ -343,4 +343,39 @@ public function type( $args, $assoc_args ) {
 		WP_CLI::line( $message );
 	}
 
+	/**
+	 * Determines whether the object cache implementation supports a particular feature.
+	 *
+	 * ## OPTIONS
+	 *
+	 * <feature>
+	 * : Name of the feature to check for.
+	 *
+	 * ## EXAMPLES
+	 *
+	 *     # Check whether is add_multiple supported.
+	 *     $ wp cache supports add_multiple
+	 *     $ echo $?
+	 *     0
+	 *
+	 *     # Bash script for checking whether for support like this:
+	 *     if ! wp cache supports non_existing; then
+	 *         echo 'non_existing is not supported'
+	 *     fi
+	 */
+	public function supports( $args, $assoc_args ) {
+		list ( $feature ) = $args;
+
+		if ( ! function_exists( 'wp_cache_supports' ) ) {
+			WP_CLI::error( 'Checking cache features is only available in WordPress 6.1 and higher' );
+		}
+
+		$supports = wp_cache_supports( $feature );
+
+		if ( $supports ) {
+			WP_CLI::halt( 0 );
+		}
+		WP_CLI::halt( 1 );
+	}
+
 }