REST API: Add support for search_columns argument to the REST API

[youknowriad]

Backports to change originally made in WordPress/gutenberg#67330

This adds support to search_columns to the user controller, mirroring a change that was done in the past for the post controller.

Trac ticket: https://core.trac.wordpress.org/ticket/62596

Todo

• Add unit test.

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Props youknowriad, ntsekouras, joemcgill, mamaduka.

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[joemcgill]

This looks good to me. It would be nice to add a PHPUnit test that confirms that users without list_users caps are not able to use the user_email search column.

[Mamaduka]

@youknowriad, here's the patch.

diff --git tests/phpunit/tests/rest-api/rest-users-controller.php tests/phpunit/tests/rest-api/rest-users-controller.php
index 009200f401..fcaf7cdf5f 100644
--- tests/phpunit/tests/rest-api/rest-users-controller.php
+++ tests/phpunit/tests/rest-api/rest-users-controller.php
@@ -713,6 +713,9 @@ class WP_Test_REST_Users_Controller extends WP_Test_REST_Controller_Testcase {
 		$this->assertCount( 0, $response->get_data() );
 	}
 
+	/**
+	 * @ticket 62596
+	 */
 	public function test_get_items_search_columns() {
 		$request = new WP_REST_Request( 'GET', '/wp/v2/users' );
 		$request->set_param( 'search', 'yololololo' );
@@ -746,6 +749,27 @@ class WP_Test_REST_Users_Controller extends WP_Test_REST_Controller_Testcase {
 		$this->assertCount( 1, $response->get_data() );
 	}
 
+	/**
+	 * @ticket 62596
+	 */
+	public function test_get_items_seach_columns_without_permission() {
+		self::factory()->user->create(
+			array(
+				'display_name' => 'Adam',
+				'user_email'   => 'yololololo@example.localhost',
+			)
+		);
+
+		// Test user without sufficient capabilities - 'list_users'.
+		wp_set_current_user( self::$editor );
+
+		$request = new WP_REST_Request( 'GET', '/wp/v2/users' );
+		$request->set_param( 'search', 'yololololo' );
+		$request->set_param( 'search_columns', 'email' );
+		$response = rest_get_server()->dispatch( $request );
+		$this->assertCount( 0, $response->get_data() );
+	}
+
 	public function test_get_items_slug_query() {
 		wp_set_current_user( self::$user );