Ticket #40444: 40444.2.patch

src/wp-includes/rest-api/class-wp-rest-server.php

@@ -252 +252 @@
                 $send_no_cache_headers = apply_filters( 'rest_send_nocache_headers', is_user_logged_in() );
                 if ( $send_no_cache_headers ) {
                         foreach ( wp_get_nocache_headers() as $header => $header_value ) {
+                                if ( empty( $header_value ) ) {
+                                        $this->clear_header( $header );
+                                        continue;
+                                }
+
                                 $this->send_header( $header, $header_value );
                         }
                 }
@@ -1261 +1266 @@
                         $this->send_header( $key, $value );
                 }
         }
+        /**
+         * Sends an HTTP header.
+         *
+         * @since 4.4.0
+         * @access public
+         *
+         * @param string $key Header key.
+         * @param string $value Header value.
+         */
+
+        /**
+         * Removes an HTTP header from the current response.
+         *
+         * @since 4.8.0
+         * @access public
+         *
+         * @param string $key Header key.
+         */
+        public function clear_header( $key ) {
+
+                // In PHP 5.3+ there is a way to remove an already set header.
+                if ( function_exists( 'header_remove' ) ) {
+                        @header_remove( $key );
+                } else {
+                        // In PHP 5.2, send an empty header, but only as a
+                        // last resort to override a header already sent.
+                        $this->send_header( $key, '' );
+                }
+        }
 
         /**
          * Retrieves the raw request entity (body).

tests/phpunit/includes/spy-rest-server.php

@@ -31 +31 @@
                 $this->sent_headers[ $header ] = $value;
         }
 
+        public function clear_header( $header ) {
+                unset( $this->sent_headers[ $header ] );
+        }
+
         /**
          * Override the dispatch method so we can get a handle on the request object.
          *

tests/phpunit/tests/rest-api/rest-server.php

@@ -763 +763 @@
                 $headers = $this->server->sent_headers;
 
                 foreach ( wp_get_nocache_headers() as $header => $value ) {
+                        if ( empty( $value ) ) {
+                                continue;
+                        }
+
                         $this->assertTrue( isset( $headers[ $header ] ), sprintf( 'Header %s is not present in the response.', $header ) );
                         $this->assertEquals( $value, $headers[ $header ] );
                 }
+
+                // Last-Modified should be unset as per #WP23021
+                $this->assertFalse( isset( $headers['Last-Modified'] ), 'Last-Modified should not be sent.' );
         }
 
         public function test_no_nocache_headers_on_unauthenticated_requests() {