add pluck command to transient

Author: petitphp

features/transient.feature

@@ -572,3 +572,53 @@ Feature: Manage WordPress transient cache
       name
       foo4
       """
+
+  Scenario: Nested values from transient can be retrieved at any depth.
+    Given a WP install
+    And a wp-content/mu-plugins/test-harness.php file:
+      """
+      <?php
+      $set_foo = function(){
+        set_transient( 'my_key', ['foo' => 'bar'] );
+        set_transient( 'my_key_2', ['foo' => ['bar' => 'baz']] );
+      };
+
+      WP_CLI::add_hook( 'before_invoke:transient pluck', $set_foo );
+      """
+
+    When I try `wp transient pluck my_key foo`
+    Then STDOUT should be:
+      """
+      bar
+      """
+
+    When I try `wp transient pluck my_key_2 foo bar`
+    Then STDOUT should be:
+      """
+      baz
+      """
+
+  Scenario: Nested values from site transient can be retrieved at any depth.
+    Given a WP multisite install
+    And I run `wp site create --slug=foo`
+    And a wp-content/mu-plugins/test-harness.php file:
+      """
+      <?php
+      $set_foo = function(){
+        set_site_transient( 'my_key', ['foo' => 'bar'] );
+      };
+
+      WP_CLI::add_hook( 'before_invoke:transient pluck', $set_foo );
+      """
+
+    When I try `wp transient pluck my_key foo --network`
+    Then STDOUT should be:
+      """
+      bar
+      """
+
+    When I try `wp transient pluck my_key foo`
+    Then STDERR should be:
+      """
+      Warning: Transient with key "my_key" is not set.
+      """

src/Transient_Command.php

@@ -1,5 +1,6 @@
 <?php
 
+use WP_CLI\Cache\RecursiveDataStructureTraverser;
 use WP_CLI\Utils;
 
 /**
@@ -404,6 +405,61 @@ public function list_( $args, $assoc_args ) {
 		$formatter->display_items( $results );
 	}
 
+	/**
+	 * Get a nested value from a transient.
+	 *
+	 * ## OPTIONS
+	 *
+	 * <key>
+	 * : Key for the transient.
+	 *
+	 * <key-path>...
+	 * : The name(s) of the keys within the value to locate the value to pluck.
+	 *
+	 * [--format=<format>]
+	 * : The output format of the value.
+	 * ---
+	 * default: plaintext
+	 * options:
+	 *   - plaintext
+	 *   - json
+	 *   - yaml
+	 * ---
+	 *
+	 * [--network]
+	 * : Get the value of a network|site transient. On single site, this is
+	 * a specially-named cache key. On multisite, this is a global cache
+	 * (instead of local to the site).
+	 */
+	public function pluck( $args, $assoc_args ) {
+		list( $key ) = $args;
+
+		$func  = Utils\get_flag_value( $assoc_args, 'network' ) ? 'get_site_transient' : 'get_transient';
+		$value = $func( $key );
+
+		if ( false === $value ) {
+			WP_CLI::warning( 'Transient with key "' . $key . '" is not set.' );
+			exit;
+		}
+
+		$key_path = array_map( function( $key ) {
+			if ( is_numeric( $key ) && ( $key === (string) intval( $key ) ) ) {
+				return (int) $key;
+			}
+			return $key;
+		}, array_slice( $args, 1 ) );
+
+		$traverser = new RecursiveDataStructureTraverser( $value );
+
+		try {
+			$value = $traverser->get( $key_path );
+		} catch ( \Exception $e ) {
+			die( 1 );
+		}
+
+		WP_CLI::print_value( $value, $assoc_args );
+	}
+
 	/**
 	 * Retrieves the expiration time.
 	 *