Add check for restricted contributors

includes/Checker/Checks/Plugin_Repo/Plugin_Readme_Check.php

@@ -651,6 +651,8 @@ private function check_for_donate_link( Check_Result $result, string $readme_fil
 	 *
 	 * @param Check_Result $result      The Check Result to amend.
 	 * @param string       $readme_file Readme file.
+	 *
+	 * @SuppressWarnings(PHPMD.ExcessiveMethodLength)
 	 */
 	private function check_for_contributors( Check_Result $result, string $readme_file ) {
 		$regex = '/Contributors\s?:(?:\*\*|\s)?(.*?)\R/';
@@ -666,7 +668,7 @@ private function check_for_contributors( Check_Result $result, string $readme_fi
 
 		$usernames = explode( ',', $matches[1] );
 
-		$usernames = array_map( 'trim', $usernames );
+		$usernames = array_unique( array_map( 'trim', $usernames ) );
 
 		$valid = true;
 
@@ -692,6 +694,72 @@ private function check_for_contributors( Check_Result $result, string $readme_fi
 				'',
 				6
 			);
+
+			return;
+		}
+
+		$restricted_contributors = $this->get_restricted_contributors();
+
+		$disallowed_contributors = array_keys(
+			array_filter(
+				$restricted_contributors,
+				function ( $value ) {
+					return 'error' === strtolower( $value );
+				}
+			)
+		);
+
+		if ( ! empty( $disallowed_contributors ) ) {
+			$disallowed_usernames = array_intersect( $usernames, $disallowed_contributors );
+
+			if ( ! empty( $disallowed_usernames ) ) {
+				$this->add_result_error_for_file(
+					$result,
+					sprintf(
+						/* translators: 1: plugin header field, 2: usernames */
+						__( 'The "%1$s" header in the readme file contains restricted username(s). Found: %2$s', 'plugin-check' ),
+						'Contributors',
+						'"' . implode( '", "', $disallowed_usernames ) . '"'
+					),
+					'readme_restricted_contributors',
+					$readme_file,
+					0,
+					0,
+					'https://developer.wordpress.org/plugins/wordpress-org/how-your-readme-txt-works/#readme-header-information',
+					7
+				);
+			}
+		}
+
+		$reserved_contributors = array_keys(
+			array_filter(
+				$restricted_contributors,
+				function ( $value ) {
+					return 'warning' === strtolower( $value );
+				}
+			)
+		);
+
+		if ( ! empty( $reserved_contributors ) ) {
+			$reserved_usernames = array_intersect( $usernames, $reserved_contributors );
+
+			if ( ! empty( $reserved_usernames ) ) {
+				$this->add_result_warning_for_file(
+					$result,
+					sprintf(
+						/* translators: 1: plugin header field, 2: usernames */
+						__( 'The "%1$s" header in the readme file contains reserved username(s). Found: %2$s', 'plugin-check' ),
+						'Contributors',
+						'"' . implode( '", "', $reserved_usernames ) . '"'
+					),
+					'readme_reserved_contributors',
+					$readme_file,
+					0,
+					0,
+					'https://developer.wordpress.org/plugins/wordpress-org/how-your-readme-txt-works/#readme-header-information',
+					6
+				);
+			}
 		}
 	}
 
@@ -762,6 +830,34 @@ private function get_ignored_warnings( Parser $parser ) {
 		return $ignored_warnings;
 	}
 
+	/**
+	 * Returns restricted contributors.
+	 *
+	 * @since 1.4.0
+	 *
+	 * @return array Restricted contributors.
+	 */
+	private function get_restricted_contributors() {
+		$restricted_contributors = array(
+			'username'                => 'error',
+			'your-username'           => 'error',
+			'your_wordpress_username' => 'error',
+			'yourusername'            => 'error',
+			'wordpressdotorg'         => 'warning',
+		);
+
+		/**
+		 * Filter the list of restricted contributors.
+		 *
+		 * @since 1.4.0
+		 *
+		 * @param array $restricted_contributors Array of restricted contributors with error type.
+		 */
+		$restricted_contributors = (array) apply_filters( 'wp_plugin_check_restricted_contributors', $restricted_contributors );
+
+		return $restricted_contributors;
+	}
+
 	/**
 	 * Gets the description for the check.
 	 *

tests/phpunit/testdata/plugins/test-plugin-plugin-readme-errors-invalid-name/readme.txt

@@ -1,6 +1,6 @@
 === Plugin Name ===
 
-Contributors:      plugin-check
+Contributors:      plugin-check, username, wordpressdotorg
 Requires at least: 6.0
 Tested up to:      6.1
 Requires PHP:      5.6

tests/phpunit/testdata/plugins/test-plugin-plugin-readme-parser-warnings/readme.txt

@@ -1,7 +1,7 @@
 
 === Test Plugin Readme Errors Parser Warnings ===
 
-Contributors:      plugin check, wordpressdotorg
+Contributors:      plugin check, johndoe
 Requires at least: 6.0
 Tested up to:      Latest
 Requires PHP:      5.6

tests/phpunit/tests/Checker/Checks/Plugin_Readme_Check_Tests.php

@@ -68,6 +68,28 @@ public function test_run_with_errors_invalid_name() {
 		$this->assertCount( 1, wp_list_filter( $errors['readme.txt'][0][0], array( 'code' => 'invalid_plugin_name' ) ) );
 	}
 
+	public function test_run_with_errors_restricted_contributors() {
+		$readme_check  = new Plugin_Readme_Check();
+		$check_context = new Check_Context( UNIT_TESTS_PLUGIN_DIR . 'test-plugin-plugin-readme-errors-invalid-name/load.php' );
+		$check_result  = new Check_Result( $check_context );
+
+		$readme_check->run( $check_result );
+
+		$errors   = $check_result->get_errors();
+		$warnings = $check_result->get_warnings();
+
+		$this->assertNotEmpty( $errors );
+		$this->assertNotEmpty( $warnings );
+		$this->assertArrayHasKey( 'readme.txt', $errors );
+		$this->assertArrayHasKey( 'readme.txt', $warnings );
+
+		// Check for restricted contributors error.
+		$this->assertCount( 1, wp_list_filter( $errors['readme.txt'][0][0], array( 'code' => 'readme_restricted_contributors' ) ) );
+
+		// Check for reserved contributors warning.
+		$this->assertCount( 1, wp_list_filter( $warnings['readme.txt'][0][0], array( 'code' => 'readme_reserved_contributors' ) ) );
+	}
+
 	public function test_run_with_errors_empty_name() {
 		$readme_check  = new Plugin_Readme_Check();
 		$check_context = new Check_Context( UNIT_TESTS_PLUGIN_DIR . 'test-plugin-plugin-readme-errors-empty-name/load.php' );