Add support for formatting boolean values in WP_CLI\Formatter

features/formatter.feature

@@ -153,3 +153,35 @@ Feature: Format output
       | gaa/gaa-log      | *          | ✔      |
       | gaa/gaa-nonsense | v3.0.11    | 🛇      |
       | gaa/gaa-100%new  | v100%new   | ✔      |
+
+  Scenario: Format data with boolean value
+    Given an empty directory
+    And a file.php file:
+      """
+      <?php
+      $items = array(
+        array(
+          'id' => 1,
+          'status' => true,
+        ),
+        array(
+          'id' => 2,
+          'status' => false,
+        ),
+      );
+      $iterator = \WP_CLI\Utils\iterator_map(
+          $items,
+          function (array $item) {
+              return $item;
+          }
+      );
+      $assoc_args = array( 'format' => 'table' );
+      $formatter = new WP_CLI\Formatter( $assoc_args, array( 'id', 'status' ) );
+      $formatter->display_items($iterator);
+      """
+
+    When I run `wp eval-file file.php --skip-wordpress`
+    Then STDOUT should be a table containing rows:
+      | id | status |
+      | 1  | true   |
+      | 2  | false  |

php/WP_CLI/Formatter.php

@@ -89,9 +89,9 @@ public function display_items( $items, $ascii_pre_colorized = false ) {
 
 			if ( in_array( $this->args['format'], [ 'table', 'csv' ], true ) ) {
 				if ( $items instanceof Iterator ) {
-					$items = Utils\iterator_map( $items, [ $this, 'transform_item_values_to_json' ] );
+					$items = Utils\iterator_map( $items, [ $this, 'transform_item_values' ] );
 				} else {
-					$items = array_map( [ $this, 'transform_item_values_to_json' ], $items );
+					$items = array_map( [ $this, 'transform_item_values' ], $items );
 				}
 			}
 
@@ -347,21 +347,37 @@ private function assoc_array_to_rows( $fields ) {
 	}
 
 	/**
-	 * Transforms objects and arrays to JSON as necessary
+	 * Transforms into shell-friendly output, as necessary
 	 *
 	 * @param mixed $item
 	 * @return mixed
 	 */
-	public function transform_item_values_to_json( $item ) {
+	public function transform_item_values( $item ) {
 		foreach ( $this->args['fields'] as $field ) {
 			$true_field = $this->find_item_key( $item, $field );
 			$value      = is_object( $item ) ? $item->$true_field : $item[ $true_field ];
+
+			// Transform into JSON.
 			if ( is_array( $value ) || is_object( $value ) ) {
 				if ( is_object( $item ) ) {
 					$item->$true_field = json_encode( $value );
 				} elseif ( is_array( $item ) ) {
 					$item[ $true_field ] = json_encode( $value );
 				}
+
+				return $item;
+			}
+
+			// Transform boolean.
+			// See: https://github.com/wp-cli/wp-cli/issues/5542
+			if ( is_bool( $value ) ) {
+				if ( is_object( $item ) ) {
+					$item->$true_field = $value ? 'true' : 'false';
+				} elseif ( is_array( $item ) ) {
+					$item[ $true_field ] = $value ? 'true' : 'false';
+				}
+
+				return $item;
 			}
 		}
 		return $item;