Add restart command and --watch option to wp shell

composer.json

@@ -12,7 +12,7 @@
         }
     ],
     "require": {
-        "wp-cli/wp-cli": "^2.12"
+        "wp-cli/wp-cli": "^2.13"
     },
     "require-dev": {
         "wp-cli/wp-cli-tests": "^5"

features/shell.feature

@@ -61,6 +61,43 @@ Feature: WordPress REPL
       """
     And STDERR should be empty
 
+  Scenario: Restart shell
+    Given a WP install
+    And a session file:
+      """
+      $a = 1;
+      restart
+      $b = 2;
+      """
+
+    When I run `wp shell --basic < session`
+    Then STDOUT should contain:
+      """
+      Restarting shell...
+      """
+    And STDOUT should contain:
+      """
+      => int(2)
+      """
+
+  Scenario: Exit shell
+    Given a WP install
+    And a session file:
+      """
+      $a = 1;
+      exit
+      """
+
+    When I run `wp shell --basic < session`
+    Then STDOUT should contain:
+      """
+      => int(1)
+      """
+    And STDOUT should not contain:
+      """
+      exit
+      """
+
   Scenario: Input starting with dash
     Given a WP install
     And a session file:

src/Shell_Command.php

@@ -13,20 +13,51 @@ class Shell_Command extends WP_CLI_Command {
 	 * is loaded, you have access to all the functions, classes and globals
 	 * that you can use within a WordPress plugin, for example.
 	 *
+	 * The `restart` command reloads the shell by spawning a new PHP process,
+	 * allowing modified code to be fully reloaded. Note that this requires
+	 * the `pcntl_exec()` function. If not available, the shell restarts
+	 * in-process, which resets variables but doesn't reload PHP files.
+	 *
 	 * ## OPTIONS
 	 *
 	 * [--basic]
 	 * : Force the use of WP-CLI's built-in PHP REPL, even if the Boris or
 	 * PsySH PHP REPLs are available.
 	 *
+	 * [--watch=<path>]
+	 * : Watch a file or directory for changes and automatically restart the shell.
+	 * Only works with the built-in REPL (--basic).
+	 *
 	 * ## EXAMPLES
 	 *
 	 *     # Call get_bloginfo() to get the name of the site.
 	 *     $ wp shell
 	 *     wp> get_bloginfo( 'name' );
 	 *     => string(6) "WP-CLI"
+	 *
+	 *     # Restart the shell to reload code changes.
+	 *     $ wp shell
+	 *     wp> restart
+	 *     Restarting shell in new process...
+	 *     wp>
+	 *
+	 *     # Watch a directory for changes and auto-restart.
+	 *     $ wp shell --watch=wp-content/plugins/my-plugin
+	 *     wp> // Make changes to files in the plugin directory
+	 *     Detected changes in wp-content/plugins/my-plugin, restarting shell...
+	 *     wp>
+	 *
+	 * @param string[] $_ Positional arguments. Unused.
+	 * @param array{basic?: bool, watch?: string} $assoc_args Associative arguments.
 	 */
 	public function __invoke( $_, $assoc_args ) {
+		$watch_path = Utils\get_flag_value( $assoc_args, 'watch', false );
+
+		if ( $watch_path && ! Utils\get_flag_value( $assoc_args, 'basic' ) ) {
+			WP_CLI::warning( 'The --watch option only works with the built-in REPL. Enabling --basic mode.' );
+			$assoc_args['basic'] = true;
+		}
+
 		$class = WP_CLI\Shell\REPL::class;
 
 		$implementations = array(
@@ -55,8 +86,108 @@ public function __invoke( $_, $assoc_args ) {
 			/**
 			 * @var class-string<WP_CLI\Shell\REPL> $class
 			 */
-			$repl = new $class( 'wp> ' );
-			$repl->start();
+			if ( $watch_path ) {
+				$watch_path = $this->resolve_watch_path( $watch_path );
+			}
+
+			do {
+				$repl = new $class( 'wp> ' );
+				if ( $watch_path ) {
+					$repl->set_watch_path( $watch_path );
+				}
+				$exit_code = $repl->start();
+
+				// If restart requested, exec a new PHP process to reload all code
+				if ( WP_CLI\Shell\REPL::EXIT_CODE_RESTART === $exit_code ) {
+					$this->restart_process( $assoc_args );
+					// If restart_process() returns, pcntl_exec is not available, continue in-process
+				}
+			} while ( WP_CLI\Shell\REPL::EXIT_CODE_RESTART === $exit_code );
+		}
+	}
+
+	/**
+	 * Resolve and validate the watch path.
+	 *
+	 * @param string $path Path to watch.
+	 * @return string|never Absolute path to watch.
+	 */
+	private function resolve_watch_path( $path ) {
+		if ( ! file_exists( $path ) ) {
+			WP_CLI::error( "Watch path does not exist: {$path}" );
+		}
+
+		$realpath = realpath( $path );
+		if ( false === $realpath ) {
+			WP_CLI::error( "Could not resolve watch path: {$path}" );
+		}
+
+		return $realpath;
+	}
+
+	/**
+	 * Restart the shell by spawning a new PHP process.
+	 *
+	 * This replaces the current process with a new one to fully reload all code.
+	 * Falls back to in-process restart if pcntl_exec is not available.
+	 *
+	 * @param array{basic?: bool, watch?: string} $assoc_args Command arguments to preserve.
+	 */
+	private function restart_process( $assoc_args ) {
+		// Check if pcntl_exec is available
+		if ( ! function_exists( 'pcntl_exec' ) ) {
+			WP_CLI::debug( 'pcntl_exec not available, falling back to in-process restart', 'shell' );
+			return;
+		}
+
+		// Build the command to restart wp shell with the same arguments
+		$php_binary = Utils\get_php_binary();
+
+		// Get the WP-CLI script path
+		$wp_cli_script = null;
+		foreach ( array( 'argv', '_SERVER' ) as $source ) {
+			if ( 'argv' === $source && is_array( $GLOBALS['argv'] ) && isset( $GLOBALS['argv'][0] ) ) {
+				$wp_cli_script = $GLOBALS['argv'][0];
+				break;
+			} elseif ( '_SERVER' === $source && is_array( $_SERVER['argv'] ) && isset( $_SERVER['argv'][0] ) ) {
+				$wp_cli_script = $_SERVER['argv'][0];
+				break;
+			}
+		}
+
+		if ( ! $wp_cli_script ) {
+			WP_CLI::debug( 'Could not determine WP-CLI script path, falling back to in-process restart', 'shell' );
+			return;
 		}
+
+		// Build arguments array
+		$args = array( $php_binary, $wp_cli_script, 'shell' );
+
+		if ( Utils\get_flag_value( $assoc_args, 'basic' ) ) {
+			$args[] = '--basic';
+		}
+
+		$watch_path = Utils\get_flag_value( $assoc_args, 'watch', false );
+		if ( $watch_path ) {
+			$args[] = '--watch=' . $watch_path;
+		}
+
+		// Add the path argument if present in $_SERVER
+		if ( isset( $_SERVER['argv'] ) && is_array( $_SERVER['argv'] ) ) {
+			foreach ( $_SERVER['argv'] as $arg ) {
+				if ( is_string( $arg ) && '--path=' === substr( $arg, 0, 7 ) ) {
+					$args[] = $arg;
+				}
+			}
+		}
+
+		WP_CLI::log( 'Restarting shell in new process...' );
+
+		// Replace the current process with a new one
+		// Note: pcntl_exec does not return on success
+		pcntl_exec( $php_binary, array_slice( $args, 1 ) );
+
+		// If we reach here, exec failed
+		WP_CLI::warning( 'Failed to restart process, falling back to in-process restart' );
 	}
 }

src/WP_CLI/Shell/REPL.php

@@ -10,21 +10,53 @@ class REPL {
 
 	private $history_file;
 
+	private $watch_path;
+
+	private $watch_mtime;
+
+	const EXIT_CODE_RESTART = 10;
+
 	public function __construct( $prompt ) {
 		$this->prompt = $prompt;
 
 		$this->set_history_file();
 	}
 
+	/**
+	 * Set a path to watch for changes.
+	 *
+	 * @param string $path Path to watch for changes.
+	 */
+	public function set_watch_path( $path ) {
+		$this->watch_path  = $path;
+		$this->watch_mtime = $this->get_recursive_mtime( $path );
+	}
+
 	public function start() {
-		// @phpstan-ignore while.alwaysTrue
 		while ( true ) {
+			// Check for file changes if watching
+			if ( $this->watch_path && $this->has_changes() ) {
+				WP_CLI::log( "Detected changes in {$this->watch_path}, restarting shell..." );
+				return self::EXIT_CODE_RESTART;
+			}
+
 			$line = $this->prompt();
 
 			if ( '' === $line ) {
 				continue;
 			}
 
+			// Check for special exit command
+			if ( 'exit' === trim( $line ) ) {
+				return 0;
+			}
+
+			// Check for special restart command
+			if ( 'restart' === trim( $line ) ) {
+				WP_CLI::log( 'Restarting shell...' );
+				return self::EXIT_CODE_RESTART;
+			}
+
 			$line = rtrim( $line, ';' ) . ';';
 
 			if ( self::starts_with( self::non_expressions(), $line ) ) {
@@ -121,7 +153,7 @@ private static function create_prompt_cmd( $prompt, $history_path ) {
 		$prompt       = escapeshellarg( $prompt );
 		$history_path = escapeshellarg( $history_path );
 		if ( getenv( 'WP_CLI_CUSTOM_SHELL' ) ) {
-			$shell_binary = getenv( 'WP_CLI_CUSTOM_SHELL' );
+			$shell_binary = (string) getenv( 'WP_CLI_CUSTOM_SHELL' );
 		} else {
 			$shell_binary = '/bin/bash';
 		}
@@ -153,4 +185,64 @@ private function set_history_file() {
 	private static function starts_with( $tokens, $line ) {
 		return preg_match( "/^($tokens)[\(\s]+/", $line );
 	}
+
+	/**
+	 * Check if the watched path has changes.
+	 *
+	 * @return bool True if changes detected, false otherwise.
+	 */
+	private function has_changes() {
+		if ( ! $this->watch_path ) {
+			return false;
+		}
+
+		$current_mtime = $this->get_recursive_mtime( $this->watch_path );
+		return $current_mtime !== $this->watch_mtime;
+	}
+
+	/**
+	 * Get the most recent modification time for a path recursively.
+	 *
+	 * @param string $path Path to check.
+	 * @return int Most recent modification time.
+	 */
+	private function get_recursive_mtime( $path ) {
+		$mtime = 0;
+
+		if ( is_file( $path ) ) {
+			$file_mtime = filemtime( $path );
+			return false !== $file_mtime ? $file_mtime : 0;
+		}
+
+		if ( is_dir( $path ) ) {
+			$dir_mtime = filemtime( $path );
+			$mtime     = false !== $dir_mtime ? $dir_mtime : 0;
+
+			try {
+				$iterator = new \RecursiveIteratorIterator(
+					new \RecursiveDirectoryIterator( $path, \RecursiveDirectoryIterator::SKIP_DOTS ),
+					\RecursiveIteratorIterator::SELF_FIRST
+				);
+
+				foreach ( $iterator as $file ) {
+					/** @var \SplFileInfo $file */
+					$file_mtime = $file->getMTime();
+					if ( $file_mtime > $mtime ) {
+						$mtime = $file_mtime;
+					}
+				}
+			} catch ( \UnexpectedValueException $e ) {
+				// Handle unreadable directories/files gracefully.
+				WP_CLI::warning(
+					sprintf(
+						'Could not read path "%s" while checking for changes: %s',
+						$path,
+						$e->getMessage()
+					)
+				);
+			}
+		}
+
+		return $mtime;
+	}
 }