REST API: Optimize themes collection response when querying active theme.

This updates `WP_REST_Themes_Controller::get_items()` to shortcut returning the current theme when the request explicitly queries for the active theme, avoiding expensive call to `wp_get_themes()`.

Developed in WordPress#11032

Follow up to r49925.

Props aduth, mukesh27, westonruter.
See #50152. 
Fixes #64719.


git-svn-id: https://develop.svn.wordpress.org/trunk@61856 602fd350-edb4-49c9-b593-d223f7449a82

Author: westonruter

src/wp-includes/rest-api/endpoints/class-wp-rest-themes-controller.php

@@ -197,18 +197,22 @@ public function get_item( $request ) {
 	public function get_items( $request ) {
 		$themes = array();
 
-		$active_themes = wp_get_themes();
 		$current_theme = wp_get_theme();
 		$status        = $request['status'];
 
-		foreach ( $active_themes as $theme ) {
-			$theme_status = ( $this->is_same_theme( $theme, $current_theme ) ) ? 'active' : 'inactive';
-			if ( is_array( $status ) && ! in_array( $theme_status, $status, true ) ) {
-				continue;
-			}
-
-			$prepared = $this->prepare_item_for_response( $theme, $request );
+		if ( array( 'active' ) === $status ) {
+			$prepared = $this->prepare_item_for_response( $current_theme, $request );
 			$themes[] = $this->prepare_response_for_collection( $prepared );
+		} else {
+			foreach ( wp_get_themes() as $theme ) {
+				$theme_status = ( $this->is_same_theme( $theme, $current_theme ) ) ? 'active' : 'inactive';
+				if ( is_array( $status ) && ! in_array( $theme_status, $status, true ) ) {
+					continue;
+				}
+
+				$prepared = $this->prepare_item_for_response( $theme, $request );
+				$themes[] = $this->prepare_response_for_collection( $prepared );
+			}
 		}
 
 		$response = rest_ensure_response( $themes );

tests/phpunit/tests/rest-api/rest-themes-controller.php

@@ -163,9 +163,53 @@ public function test_register_routes() {
 	 *
 	 * @ticket 45016
 	 * @ticket 61021
-	 * @ticket 62574.
+	 * @ticket 62574
 	 */
 	public function test_get_items() {
+		wp_set_current_user( self::$admin_id );
+		$request = new WP_REST_Request( 'GET', self::$themes_route );
+
+		$response = rest_get_server()->dispatch( $request );
+
+		$this->assertSame( 200, $response->get_status() );
+		$data = $response->get_data();
+
+		$fields = array(
+			'_links',
+			'author',
+			'author_uri',
+			'description',
+			'is_block_theme',
+			'name',
+			'requires_php',
+			'requires_wp',
+			'screenshot',
+			'status',
+			'stylesheet',
+			'stylesheet_uri',
+			'tags',
+			'template',
+			'template_uri',
+			'textdomain',
+			'theme_uri',
+			'version',
+		);
+		$this->assertIsArray( $data );
+		$this->assertNotEmpty( $data );
+		$this->assertSameSets( $fields, array_keys( $data[0] ) );
+
+		$this->assertContains( 'twentytwenty', wp_list_pluck( $data, 'stylesheet' ) );
+		$this->assertContains( get_stylesheet(), wp_list_pluck( $data, 'stylesheet' ) );
+	}
+
+	/**
+	 * Test retrieving a collection of active themes.
+	 *
+	 * @ticket 64719
+	 */
+	public function test_get_items_active() {
+		wp_set_current_user( self::$admin_id );
+
 		$response = self::perform_active_theme_request();
 
 		$this->assertSame( 200, $response->get_status() );
@@ -196,8 +240,9 @@ public function test_get_items() {
 			'version',
 		);
 		$this->assertIsArray( $data );
-		$this->assertNotEmpty( $data );
+		$this->assertCount( 1, $data );
 		$this->assertSameSets( $fields, array_keys( $data[0] ) );
+		$this->assertEquals( array( 'rest-api' ), wp_list_pluck( $data, 'stylesheet' ) );
 	}
 
 	/**