Issue #842: Handle 'Closure' callbacks in get_plugin().

Also, address a Travis error.
Instead of testing for the presence of 'amp-wp,'
simply make it 'amp.'
This plugin seems to be in the directory 'amp-wp'
in the Travis tests.

includes/utils/class-amp-validation-utils.php

@@ -358,21 +358,22 @@ public static function callback_wrappers() {
 	 * @return string|null $plugin   The plugin to which the callback belongs, or null.
 	 */
 	public static function get_plugin( $callback ) {
-		// The $callback is a function or static method.
 		if ( is_string( $callback ) && is_callable( $callback ) ) {
+			// The $callback is a function or static method.
 			$exploded_callback = explode( '::', $callback );
 			if ( count( $exploded_callback ) > 1 ) {
 				$reflection = new ReflectionClass( $exploded_callback[0] );
-				$file       = $reflection->getFileName();
 			} else {
 				$reflection = new ReflectionFunction( $callback );
-				$file       = $reflection->getFileName();
 			}
-		} elseif ( isset( $callback[0], $callback[1] ) && method_exists( $callback[0], $callback[1] ) ) {
+		} elseif ( is_array( $callback ) && isset( $callback[0], $callback[1] ) && method_exists( $callback[0], $callback[1] ) ) {
+			// The $callback is a method.
 			$reflection = new ReflectionClass( $callback[0] );
-			$file       = $reflection->getFileName();
+		} elseif ( is_object( $callback ) && ( 'Closure' === get_class( $callback ) ) ) {
+			$reflection = new ReflectionFunction( $callback );
 		}
 
+		$file = isset( $reflection ) ? $reflection->getFileName() : null;
 		if ( ! isset( $file ) ) {
 			return null;
 		}

tests/test-class-amp-validation-utils.php

@@ -436,16 +436,16 @@ public function test_callback_wrappers() {
 		do_action( $action_no_argument );
 		$output = ob_get_clean();
 		$this->assertContains( '<div></div>', $output );
-		$this->assertContains( '<!--before:amp-->', $output );
-		$this->assertContains( '<!--after:amp-->', $output );
+		$this->assertContains( '<!--before:amp', $output );
+		$this->assertContains( '<!--after:amp', $output );
 
 		ob_start();
 		do_action( $action_one_argument, $notice );
 		$output = ob_get_clean();
 		$this->assertContains( $notice, $output );
 		$this->assertContains( sprintf( '<div class="notice notice-warning"><p>%s</p></div>', $notice ), $output );
-		$this->assertContains( '<!--before:amp-->', $output );
-		$this->assertContains( '<!--after:amp-->', $output );
+		$this->assertContains( '<!--before:amp', $output );
+		$this->assertContains( '<!--after:amp', $output );
 
 		ob_start();
 		do_action( $action_two_arguments, $notice, get_the_ID() );
@@ -454,8 +454,8 @@ public function test_callback_wrappers() {
 		self::output_message( $notice, get_the_ID() );
 		$expected_output = ob_get_clean();
 		$this->assertContains( $expected_output, $output );
-		$this->assertContains( '<!--before:amp-->', $output );
-		$this->assertContains( '<!--after:amp-->', $output );
+		$this->assertContains( '<!--before:amp', $output );
+		$this->assertContains( '<!--after:amp', $output );
 
 		// This action's callback isn't from a plugin, so it shouldn't be wrapped in comments.
 		ob_start();
@@ -501,10 +501,11 @@ public function test_wrapped_callback() {
 		call_user_func( $wrapped_callback );
 		$output = ob_get_clean();
 
+		$this->assertEquals( 'Closure', get_class( $wrapped_callback ) );
 		$this->assertTrue( is_object( $wrapped_callback ) );
 		$this->assertContains( strval( get_the_ID() ), $output );
-		$this->assertContains( '<!--before:amp-->', $output );
-		$this->assertContains( '<!--after:amp-->', $output );
+		$this->assertContains( '<!--before:amp', $output );
+		$this->assertContains( '<!--after:amp', $output );
 		unset( $post );
 	}
 	/**