Repurpose --quiet flag to suppress automatic REPL output

features/shell.feature

@@ -151,3 +151,49 @@ Feature: WordPress REPL
       Error: The 'shutdown' hook has not fired yet
       """
     And the return code should be 1
+
+  Scenario: Quiet mode suppresses return value output
+    Given a WP install
+    And a session file:
+      """
+      $a = "hello";
+      """
+
+    When I run `wp shell --basic --quiet < session`
+    Then STDOUT should be empty
+
+  Scenario: Quiet mode still shows echo output
+    Given a WP install
+    And a session file:
+      """
+      echo "test output";
+      """
+
+    When I run `wp shell --basic --quiet < session`
+    Then STDOUT should contain:
+      """
+      test output
+      """
+
+  Scenario: Quiet mode with expression
+    Given a WP install
+    And a session file:
+      """
+      get_bloginfo('name');
+      """
+
+    When I run `wp shell --basic --quiet < session`
+    Then STDOUT should be empty
+
+  Scenario: Normal mode shows return value
+    Given a WP install
+    And a session file:
+      """
+      $a = "hello";
+      """
+
+    When I run `wp shell --basic < session`
+    Then STDOUT should contain:
+      """
+      string(5) "hello"
+      """

src/Shell_Command.php

@@ -36,6 +36,11 @@ class Shell_Command extends WP_CLI_Command {
 	 *
 	 *     # Start a shell, ensuring the 'init' hook has already fired.
 	 *     $ wp shell --hook=init
+	 *
+	 *     # Start a shell in quiet mode, suppressing return value output.
+	 *     $ wp shell --quiet
+	 *     wp> $a = "hello";
+	 *     wp>
 	 */
 	public function __invoke( $_, $assoc_args ) {
 		$hook = Utils\get_flag_value( $assoc_args, 'hook', '' );
@@ -71,6 +76,7 @@ public function __invoke( $_, $assoc_args ) {
 	 */
 	private function start_shell( $assoc_args ) {
 		$class = WP_CLI\Shell\REPL::class;
+		$quiet = (bool) WP_CLI::get_config( 'quiet' );
 
 		$implementations = array(
 			\Psy\Shell::class,
@@ -94,11 +100,14 @@ private function start_shell( $assoc_args ) {
 		if ( \Psy\Shell::class === $class ) {
 			$shell = new Psy\Shell();
 			$shell->run();
+		} elseif ( \Boris\Boris::class === $class ) {
+			$boris = new \Boris\Boris( 'wp> ' );
+			$boris->start();
 		} else {
 			/**
 			 * @var class-string<WP_CLI\Shell\REPL> $class
 			 */
-			$repl = new $class( 'wp> ' );
+			$repl = new $class( 'wp> ', $quiet );
 			$repl->start();
 		}
 	}

src/WP_CLI/Shell/REPL.php

@@ -10,8 +10,16 @@ class REPL {
 
 	private $history_file;
 
-	public function __construct( $prompt ) {
+	/** @var bool Whether to suppress automatic output. */
+	private $quiet;
+
+	/**
+	 * @param string $prompt Prompt to display.
+	 * @param bool   $quiet  Whether to suppress automatic output.
+	 */
+	public function __construct( $prompt, $quiet = false ) {
 		$this->prompt = $prompt;
+		$this->quiet  = $quiet;
 
 		$this->set_history_file();
 	}
@@ -49,8 +57,11 @@ public function start() {
 				if ( 0 < strlen( $__repl_output ) ) {
 					echo rtrim( $__repl_output, "\n" ) . "\n";
 				}
-				echo '=> ';
-				var_dump( $__repl_eval_result );
+				ob_start();
+				if ( ! $this->quiet ) {
+					echo '=> ';
+					var_dump( $__repl_eval_result );
+				}
 				fwrite( STDOUT, (string) ob_get_clean() );
 			}
 		}