Ticket #20564: 20564.25.diff

src/wp-admin/includes/post.php

@@ -1961 +1961 @@
                  * @param array $new_autosave Post array - the autosave that is about to be saved.
                  */
                 do_action( 'wp_creating_autosave', $new_autosave );
-
+                wp_autosave_post_revisioned_meta_fields( $new_autosave );
                 return wp_update_post( $new_autosave );
         }
 
@@ -1969 +1969 @@
         $post_data = wp_unslash( $post_data );
 
         // Otherwise create the new autosave as a special post revision.
-        return _wp_put_post_revision( $post_data, true );
+        $revision = _wp_put_post_revision( $post_data, true );
+
+        // Update the revisioned meta data as well.
+        wp_autosave_post_revisioned_meta_fields( get_post( $revision, ARRAY_A ) );
+        return $revision;
+}
+
+/**
+ * Autosave the revisioned meta fields.
+ *
+ * Iterates thru the revisioned meta fields and checks each to see if they are set,
+ * and have a changed value. If so, the meta value is saved and attached to the autosave.
+ *
+ * @since 6.4.0
+ *
+ * @param array $new_autosave The new post data being autosaved.
+ */
+function wp_autosave_post_revisioned_meta_fields( $new_autosave ) {
+        /*
+         * The post data arrives as either $_POST['data']['wp_autosave'] or the $_POST
+         * itself. This sets $posted_data to the correct variable.
+         *
+         * Ignoring sanitization to avoid altering meta. Ignoring the nonce check because
+         * this is hooked on inner core hooks where a valid nonce was already checked.
+         *
+         * @phpcs:disable WordPress.Security
+         */
+        $posted_data = isset( $_POST['data']['wp_autosave'] ) ? $_POST['data']['wp_autosave'] : $_POST;
+        // phpcs:enable
+
+        $post_type = get_post_type( $new_autosave['post_parent'] );
+
+        /*
+         * Go thru the revisioned meta keys and save them as part of the autosave, if
+         * the meta key is part of the posted data, the meta value is not blank and
+         * the the meta value has changes from the last autosaved value.
+         */
+        foreach ( wp_post_revision_meta_keys( $post_type ) as $meta_key ) {
+
+                if (
+                isset( $posted_data[ $meta_key ] ) &&
+                get_post_meta( $new_autosave['ID'], $meta_key, true ) !== wp_unslash( $posted_data[ $meta_key ] )
+                ) {
+                        /*
+                         * Use the underlying delete_metadata() and add_metadata() functions
+                         * vs delete_post_meta() and add_post_meta() to make sure we're working
+                         * with the actual revision meta.
+                         */
+                        delete_metadata( 'post', $new_autosave['ID'], $meta_key );
+
+                        /*
+                         * One last check to ensure meta value not empty().
+                         */
+                        if ( ! empty( $posted_data[ $meta_key ] ) ) {
+                                /*
+                                 * Add the revisions meta data to the autosave.
+                                 */
+                                add_metadata( 'post', $new_autosave['ID'], $meta_key, $posted_data[ $meta_key ] );
+                        }
+                }
+        }
 }
 
 /**

src/wp-includes/default-filters.php

@@ -414 +414 @@
 add_action( 'plugins_loaded', 'wp_maybe_load_embeds', 0 );
 add_action( 'shutdown', 'wp_ob_end_flush_all', 1 );
 // Create a revision whenever a post is updated.
+add_action( 'wp_after_insert_post', 'wp_save_post_revision_on_insert', 9, 3 );
 add_action( 'post_updated', 'wp_save_post_revision', 10, 1 );
 add_action( 'publish_post', '_publish_post_hook', 5, 1 );
 add_action( 'transition_post_status', '_transition_post_status', 5, 3 );
@@ -721 +722 @@
 // CPT wp_block custom postmeta field.
 add_action( 'init', 'wp_create_initial_post_meta' );
 
+// Include revisioned meta when considering whether a post revision has changed.
+add_filter( 'wp_save_post_revision_post_has_changed', 'wp_check_revisioned_meta_fields_have_changed', 10, 3 );
+
+// Save revisioned post meta immediately after a revision is saved
+add_action( '_wp_put_post_revision', 'wp_save_revisioned_meta_fields', 10, 2 );
+
 // Font management.
 add_action( 'wp_head', 'wp_print_font_faces', 50 );
 

src/wp-includes/meta.php

@@ -1367 +1367 @@
  * @since 4.9.8 The `$object_subtype` argument was added to the arguments array.
  * @since 5.3.0 Valid meta types expanded to include "array" and "object".
  * @since 5.5.0 The `$default` argument was added to the arguments array.
+ * @since 6.4.0 The `$revisions_enabled` argument was added to the arguments array.
  *
  * @param string       $object_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
  *                                  or any other object type with an associated meta table.
@@ -1392 +1393 @@
  *                                         support for custom fields for registered meta to be accessible via REST.
  *                                         When registering complex meta values this argument may optionally be an
  *                                         array with 'schema' or 'prepare_callback' keys instead of a boolean.
+ *     @type bool       $revisions_enabled Whether to enable revisions support for this meta_key. Can only be used when the
+ *                                         object type is 'post'.
  * }
  * @param string|array $deprecated Deprecated. Use `$args` instead.
  * @return bool True if the meta key was successfully registered in the global array, false if not.
@@ -1414 +1417 @@
                 'sanitize_callback' => null,
                 'auth_callback'     => null,
                 'show_in_rest'      => false,
+                'revisions_enabled' => false,
         );
 
         // There used to be individual args for sanitize and auth callbacks.

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

@@ -24 +24 @@
          */
         private $parent_post_type;
 
+        /**
+         * Instance of a revision meta fields object.
+         *
+         * @since 4.7.0
+         * @var WP_REST_Post_Meta_Fields
+         */
+        protected $meta;
+
         /**
          * Parent controller.
          *
@@ -60 +68 @@
                 $this->rest_base         = 'revisions';
                 $this->parent_base       = ! empty( $post_type_object->rest_base ) ? $post_type_object->rest_base : $post_type_object->name;
                 $this->namespace         = ! empty( $post_type_object->rest_namespace ) ? $post_type_object->rest_namespace : 'wp/v2';
+                $this->meta              = new WP_REST_Post_Meta_Fields( $parent_post_type );
         }
 
         /**
@@ -618 +627 @@
                         );
                 }
 
+                if ( rest_is_field_included( 'meta', $fields ) ) {
+                        $data['meta'] = $this->meta->get_value( $post->ID, $request );
+                }
+
                 $context  = ! empty( $request['context'] ) ? $request['context'] : 'view';
                 $data     = $this->add_additional_fields_to_object( $data, $request );
                 $data     = $this->filter_response_by_context( $data, $context );
@@ -751 +764 @@
                         $schema['properties']['guid'] = $parent_schema['properties']['guid'];
                 }
 
+                $schema['properties']['meta'] = $this->meta->get_field_schema();
+
                 $this->schema = $schema;
 
                 return $this->add_additional_fields_schema( $this->schema );

src/wp-includes/revision.php

@@ -95 +95 @@
         return $revision_data;
 }
 
+/**
+ * Saves revisions for a post after all changes have been made.
+ *
+ * @since 6.4.0
+ *
+ * @param int     $post_id The post id that was inserted.
+ * @param WP_Post $post    The post object that was inserted.
+ * @param bool    $update  Whether this insert is updating an existing post.
+ */
+function wp_save_post_revision_on_insert( $post_id, $post, $update ) {
+        if ( ! $update ) {
+                return;
+        }
+
+        if ( ! has_action( 'post_updated', 'wp_save_post_revision' ) ) {
+                return;
+        }
+
+        wp_save_post_revision( $post_id );
+}
+
 /**
  * Creates a revision for the current version of a post.
  *
@@ -111 +132 @@
                 return;
         }
 
+        // Prevent saving post revisions if revisions should be saved on wp_after_insert_post.
+        if ( doing_action( 'post_updated' ) && has_action( 'wp_after_insert_post', 'wp_save_post_revision_on_insert' ) ) {
+                return;
+        }
+
         $post = get_post( $post_id );
 
         if ( ! $post ) {
@@ -361 +387 @@
                  * Fires once a revision has been saved.
                  *
                  * @since 2.6.0
+                 * @since 6.4.0 The post_id parameter was added.
                  *
                  * @param int $revision_id Post revision ID.
+                 * @param int $post_id     Post ID.
                  */
-                do_action( '_wp_put_post_revision', $revision_id );
+                do_action( '_wp_put_post_revision', $revision_id, $post['post_parent'] );
         }
 
         return $revision_id;
 }
 
+
+/**
+ * Save the revisioned meta fields.
+ *
+ * @param int $revision_id The ID of the revision to save the meta to.
+ * @param int $post_id     The ID of the post the revision is associated with.
+ *
+ * @since 6.4.0
+ */
+function wp_save_revisioned_meta_fields( $revision_id, $post_id ) {
+
+        // Save revisioned meta fields.
+        foreach ( wp_post_revision_meta_keys( get_post_type( $post_id ) ) as $meta_key ) {
+                if ( metadata_exists( 'post', $post_id, $meta_key ) ) {
+                        _wp_copy_post_meta( $post_id, $revision_id, $meta_key );
+                }
+        }
+}
+
 /**
  * Gets a post revision.
  *
@@ -450 +497 @@
         // Update last edit user.
         update_post_meta( $post_id, '_edit_last', get_current_user_id() );
 
+        // Restore any revisioned meta fields.
+        wp_restore_post_revision_meta( $post_id, $revision['ID'] );
+
         /**
          * Fires after a post revision has been restored.
          *
@@ -463 +513 @@
         return $post_id;
 }
 
+/**
+ * Restore the revisioned meta values for a post.
+ *
+ * @param int $post_id     The ID of the post to restore the meta to.
+ * @param int $revision_id The ID of the revision to restore the meta from.
+ *
+ * @since 6.4.0
+ */
+function wp_restore_post_revision_meta( $post_id, $revision_id ) {
+
+        // Restore revisioned meta fields.
+        foreach ( wp_post_revision_meta_keys( get_post_type( $post_id ) ) as $meta_key ) {
+
+                // Clear any existing meta.
+                delete_post_meta( $post_id, $meta_key );
+
+                _wp_copy_post_meta( $revision_id, $post_id, $meta_key );
+        }
+}
+
+/**
+ * Copy post meta for the given key from one post to another.
+ *
+ * @param int    $source_post_id Post ID to copy meta value(s) from.
+ * @param int    $target_post_id Post ID to copy meta value(s) to.
+ * @param string $meta_key       Meta key to copy.
+ *
+ * @since 6.4.0
+ */
+function _wp_copy_post_meta( $source_post_id, $target_post_id, $meta_key ) {
+
+        foreach ( get_post_meta( $source_post_id, $meta_key ) as $meta_value ) {
+                /**
+                 * We use add_metadata() function vs add_post_meta() here
+                 * to allow for a revision post target OR regular post.
+                 */
+                add_metadata( 'post', $target_post_id, $meta_key, wp_slash( $meta_value ) );
+        }
+}
+
+/**
+ * Determine which post meta fields should be revisioned.
+ *
+ * @since 6.4.0
+ *
+ * @param string $post_type The post type being revisioned.
+ *
+ * @return array An array of meta keys to be revisioned.
+ */
+function wp_post_revision_meta_keys( $post_type ) {
+        $registered_meta = array_merge(
+                get_registered_meta_keys( 'post' ),
+                get_registered_meta_keys( 'post', $post_type )
+        );
+
+        $wp_revisioned_meta_keys = array();
+
+        foreach ( $registered_meta as $name => $args ) {
+                if ( $args['revisions_enabled'] ) {
+                        $wp_revisioned_meta_keys[ $name ] = true;
+                }
+        }
+
+        $wp_revisioned_meta_keys = array_keys( $wp_revisioned_meta_keys );
+
+        /**
+         * Filter the list of post meta keys to be revisioned.
+         *
+         * @since 6.4.0
+         *
+         * @param array $keys       An array of meta fields to be revisioned.
+         * @param string $post_type The post type being revisioned.
+         */
+        return apply_filters( 'wp_post_revision_meta_keys', $wp_revisioned_meta_keys, $post_type );
+}
+
+/**
+ * Check whether revisioned post meta fields have changed.
+ *
+ * @param bool    $post_has_changed Whether the post has changed.
+ * @param WP_Post $last_revision    The last revision post object.
+ * @param WP_Post $post             The post object.
+ *
+ * @since 6.4.0
+ */
+function wp_check_revisioned_meta_fields_have_changed( $post_has_changed, WP_Post $last_revision, WP_Post $post ) {
+        foreach ( wp_post_revision_meta_keys( $post->post_type ) as $meta_key ) {
+                if ( get_post_meta( $post->ID, $meta_key ) !== get_post_meta( $last_revision->ID, $meta_key ) ) {
+                        $post_has_changed = true;
+                        break;
+                }
+        }
+        return $post_has_changed;
+}
+
 /**
  * Deletes a revision.
  *
@@ -728 +873 @@
 
         add_filter( 'get_the_terms', '_wp_preview_terms_filter', 10, 3 );
         add_filter( 'get_post_metadata', '_wp_preview_post_thumbnail_filter', 10, 3 );
+        add_filter( 'get_post_metadata', '_wp_preview_meta_filter', 10, 4 );
 
         return $post;
 }
@@ -946 +1092 @@
 
         return true;
 }
+
+/**
+ * Filters preview post meta retrieval to get values from the autosave.
+ *
+ * Filters revisioned meta keys only.
+ *
+ * @since 6.4.0
+ *
+ * @param mixed  $value     Meta value to filter.
+ * @param int    $object_id Object ID.
+ * @param string $meta_key  Meta key to filter a value for.
+ * @param bool   $single    Whether to return a single value. Default false.
+ * @return mixed Original meta value if the meta key isn't revisioned, the object doesn't exist,
+ *               the post type is a revision or the post ID doesn't match the object ID.
+ *               Otherwise, the revisioned meta value is returned for the preview.
+ */
+function _wp_preview_meta_filter( $value, $object_id, $meta_key, $single ) {
+
+        $post = get_post();
+        if (
+                empty( $post ) ||
+                $post->ID !== $object_id ||
+                ! in_array( $meta_key, wp_post_revision_meta_keys( $post->post_type ), true ) ||
+                'revision' === $post->post_type
+        ) {
+                return $value;
+        }
+
+        $preview = wp_get_post_autosave( $post->ID );
+        if ( ! is_object( $preview ) ) {
+                return $value;
+        }
+
+        return get_post_meta( $preview->ID, $meta_key, $single );
+}

tests/phpunit/tests/meta/registerMeta.php

@@ -97 +97 @@
                                                 'sanitize_callback' => null,
                                                 'auth_callback'     => '__return_true',
                                                 'show_in_rest'      => false,
+                                                'revisions_enabled' => false,
                                         ),
                                 ),
                         ),
@@ -121 +122 @@
                                                 'sanitize_callback' => null,
                                                 'auth_callback'     => '__return_true',
                                                 'show_in_rest'      => false,
+                                                'revisions_enabled' => false,
                                         ),
                                 ),
                         ),
@@ -175 +177 @@
                                                 'sanitize_callback' => array( $this, '_new_sanitize_meta_cb' ),
                                                 'auth_callback'     => '__return_true',
                                                 'show_in_rest'      => false,
+                                                'revisions_enabled' => false,
                                         ),
                                 ),
                         ),
@@ -342 +345 @@
                                                 'sanitize_callback' => null,
                                                 'auth_callback'     => '__return_true',
                                                 'show_in_rest'      => false,
+                                                'revisions_enabled' => false,
                                         ),
                                 ),
                         ),
@@ -395 +399 @@
                                                 'sanitize_callback' => null,
                                                 'auth_callback'     => '__return_true',
                                                 'show_in_rest'      => false,
+                                                'revisions_enabled' => false,
                                         ),
                                 ),
                         ),

new file tests/phpunit/tests/post/metaRevisions.php

@@ +1 @@
+<?php
+
+/**
+ *
+ * Tests for post meta revisioning.
+ *
+ * @group post
+ * @group revision
+ * @group meta
+ * @group meta-revisions
+ */
+class MetaRevisionTests extends WP_UnitTestCase {
+
+        /**
+         * Callback function to add the revisioned keys.
+         *
+         * @param array $keys The array of revisioned keys.
+         *
+         * @return array
+         */
+        public function add_revisioned_keys( $keys ) {
+                $keys[] = 'meta_revision_test';
+                $keys[] = 'meta_multiples_test';
+                return $keys;
+        }
+
+        /**
+         * Test the revisions system for storage of meta values with slashes.
+         *
+         * @param string $passed   The passed data for testing.
+         *
+         * @param string $expected The expected value after storing & retrieving.
+         *
+         * @group revision
+         * @group slashed
+         * @dataProvider slashed_data_provider
+         */
+        public function test_revisions_stores_meta_values_with_slashes( $passed, $expected ) {
+                // Set up a new post.
+                $post_id = $this->factory->post->create();
+
+                // And update to store an initial revision.
+                wp_update_post(
+                        array(
+                                'post_content' => 'some initial content',
+                                'ID'           => $post_id,
+                        )
+                );
+                add_filter( 'wp_post_revision_meta_keys', array( $this, 'add_revisioned_keys' ) );
+
+                // Store a custom meta value, which is not revisioned by default.
+                update_post_meta( $post_id, 'meta_revision_test', wp_slash( $passed ) );
+                $this->assertEquals( $expected, get_post_meta( $post_id, 'meta_revision_test', true ) );
+
+                // Update the post, storing a revision.
+                wp_update_post(
+                        array(
+                                'post_content' => 'some more content',
+                                'ID'           => $post_id,
+                        )
+                );
+
+                // Overwrite.
+                update_post_meta( $post_id, 'meta_revision_test', 'original' );
+                // Update the post, storing a revision.
+                wp_update_post(
+                        array(
+                                'post_content' => 'some more content again',
+                                'ID'           => $post_id,
+                        )
+                );
+
+                // Restore the previous revision.
+                $revisions = (array) wp_get_post_revisions( $post_id );
+
+                // Go back to load the previous revision.
+                array_shift( $revisions );
+                $last_revision = array_shift( $revisions );
+
+                // Restore!
+                wp_restore_post_revision( $last_revision->ID );
+
+                $this->assertEquals( $expected, get_post_meta( $post_id, 'meta_revision_test', true ) );
+        }
+
+        /**
+         * Provide data for the slashed data tests.
+         */
+        public function slashed_data_provider() {
+                return array(
+                        array(
+                                'some\text',
+                                'some\text',
+                        ),
+                        array(
+                                'test some\ \\extra \\\slashed \\\\text ',
+                                'test some\ \\extra \\\slashed \\\\text ',
+                        ),
+                        array(
+                                "This \'is\' an example \n of a \"quoted\" string",
+                                "This \'is\' an example \n of a \"quoted\" string",
+                        ),
+                        array(
+                                'some unslashed text just to test! % & * ( ) #',
+                                'some unslashed text just to test! % & * ( ) #',
+                        ),
+                );
+        }
+
+        /**
+         * Test the revisions system for storage of meta values.
+         *
+         * @group revision
+         */
+        public function test_revisions_stores_meta_values() {
+                /*
+                 * Set Up.
+                 */
+
+                // Set up a new post.
+                $post_id          = $this->factory->post->create();
+                $original_post_id = $post_id;
+
+                // And update to store an initial revision.
+                wp_update_post(
+                        array(
+                                'post_content' => 'some initial content',
+                                'ID'           => $post_id,
+                        )
+                );
+
+                // One revision so far.
+                $revisions = wp_get_post_revisions( $post_id );
+                $this->assertCount( 1, $revisions );
+
+                /*
+                 * First set up a meta value.
+                 */
+
+                // Store a custom meta value, which is not revisioned by default.
+                update_post_meta( $post_id, 'meta_revision_test', 'original' );
+
+                // Update the post, storing a revision.
+                wp_update_post(
+                        array(
+                                'post_content' => 'some more content',
+                                'ID'           => $post_id,
+                        )
+                );
+
+                $revisions = wp_get_post_revisions( $post_id );
+                $this->assertCount( 2, $revisions );
+
+                // Next, store some updated meta values for the same key.
+                update_post_meta( $post_id, 'meta_revision_test', 'update1' );
+
+                // Save the post, changing content to force a revision.
+                wp_update_post(
+                        array(
+                                'post_content' => 'some updated content',
+                                'ID'           => $post_id,
+                        )
+                );
+
+                $revisions = wp_get_post_revisions( $post_id );
+                $this->assertCount( 3, $revisions );
+
+                /*
+                 * Now restore the original revision.
+                 */
+
+                // Restore the previous revision.
+                $revisions = (array) wp_get_post_revisions( $post_id );
+
+                // Go back two to load the previous revision.
+                array_shift( $revisions );
+                $last_revision = array_shift( $revisions );
+
+                // Restore!
+                wp_restore_post_revision( $last_revision->ID );
+
+                wp_update_post( array( 'ID' => $post_id ) );
+                $revisions = wp_get_post_revisions( $post_id );
+                $this->assertCount( 4, $revisions );
+
+                /*
+                 * Check the meta values to verify they are NOT revisioned - they are not revisioned by default.
+                 */
+
+                // Custom post meta should NOT be restored, orignal value should not be restored, value still 'update1'.
+                $this->assertEquals( 'update1', get_post_meta( $post_id, 'meta_revision_test', true ) );
+
+                update_post_meta( $post_id, 'meta_revision_test', 'update2' );
+
+                /*
+                 * Test the revisioning of custom meta when enabled by the wp_post_revision_meta_keys filter.
+                 */
+
+                // Add the custom field to be revised via the wp_post_revision_meta_keys filter.
+                add_filter( 'wp_post_revision_meta_keys', array( $this, 'add_revisioned_keys' ) );
+
+                // Save the post, changing content to force a revision.
+                wp_update_post(
+                        array(
+                                'post_content' => 'more updated content',
+                                'ID'           => $post_id,
+                        )
+                );
+
+                $revisions = array_values( wp_get_post_revisions( $post_id ) );
+                $this->assertCount( 5, $revisions );
+                $this->assertEquals( 'update2', get_post_meta( $revisions[0]->ID, 'meta_revision_test', true ) );
+
+                // Store custom meta values, which should now be revisioned.
+                update_post_meta( $post_id, 'meta_revision_test', 'update3' );
+
+                /*
+                 * Save the post again, custom meta should now be revisioned.
+                 *
+                 * Note that a revision is saved even though there is no change
+                 * in post content, because the revisioned post_meta has changed.
+                 */
+                wp_update_post(
+                        array(
+                                'ID' => $post_id,
+                        )
+                );
+
+                // This revision contains the existing post meta ('update3').
+                $revisions = wp_get_post_revisions( $post_id );
+                $this->assertCount( 6, $revisions );
+
+                // Verify that previous post meta is set.
+                $this->assertEquals( 'update3', get_post_meta( $post_id, 'meta_revision_test', true ) );
+
+                // Restore the previous revision.
+                $revisions = wp_get_post_revisions( $post_id );
+
+                // Go back two to load the previous revision.
+                array_shift( $revisions );
+                $last_revision = array_shift( $revisions );
+                wp_restore_post_revision( $last_revision->ID );
+
+                /*
+                 * Verify that previous post meta is restored.
+                 */
+                $this->assertEquals( 'update2', get_post_meta( $post_id, 'meta_revision_test', true ) );
+
+                // Try storing a blank meta.
+                update_post_meta( $post_id, 'meta_revision_test', '' );
+                wp_update_post(
+                        array(
+                                'ID' => $post_id,
+                        )
+                );
+
+                update_post_meta( $post_id, 'meta_revision_test', 'update 4' );
+                wp_update_post(
+                        array(
+                                'ID' => $post_id,
+                        )
+                );
+
+                // Restore the previous revision.
+                $revisions = wp_get_post_revisions( $post_id );
+                array_shift( $revisions );
+                $last_revision = array_shift( $revisions );
+                wp_restore_post_revision( $last_revision->ID );
+
+                /*
+                 * Verify that previous blank post meta is restored.
+                 */
+                $this->assertEquals( '', get_post_meta( $post_id, 'meta_revision_test', true ) );
+
+                /*
+                 * Test not tracking a key - remove the key from the revisioned meta.
+                 */
+                remove_all_filters( 'wp_post_revision_meta_keys' );
+
+                // Meta should no longer be revisioned.
+                update_post_meta( $post_id, 'meta_revision_test', 'update 5' );
+                wp_update_post(
+                        array(
+                                'ID'           => $post_id,
+                                'post_content' => 'changed content',
+                        )
+                );
+                update_post_meta( $post_id, 'meta_revision_test', 'update 6' );
+                wp_update_post(
+                        array(
+                                'ID'           => $post_id,
+                                'post_content' => 'go updated content',
+                        )
+                );
+
+                // Restore the previous revision.
+                $revisions = wp_get_post_revisions( $post_id );
+                array_shift( $revisions );
+                $last_revision = array_shift( $revisions );
+                wp_restore_post_revision( $last_revision->ID );
+
+                /*
+                 * Verify that previous post meta is NOT restored.
+                 */
+                $this->assertEquals( 'update 6', get_post_meta( $post_id, 'meta_revision_test', true ) );
+
+                // Add the custom field to be revised via the wp_post_revision_meta_keys filter.
+                add_filter( 'wp_post_revision_meta_keys', array( $this, 'add_revisioned_keys' ) );
+
+                /*
+                 * Test the revisioning of multiple meta keys.
+                 */
+
+                // Add three values for meta.
+                update_post_meta( $post_id, 'meta_revision_test', 'update 7' );
+                add_post_meta( $post_id, 'meta_revision_test', 'update 7 number 2' );
+                add_post_meta( $post_id, 'meta_revision_test', 'update 7 number 3' );
+                wp_update_post( array( 'ID' => $post_id ) );
+
+                // Update all three values.
+                update_post_meta( $post_id, 'meta_revision_test', 'update 8', 'update 7' );
+                update_post_meta( $post_id, 'meta_revision_test', 'update 8 number 2', 'update 7 number 2' );
+                update_post_meta( $post_id, 'meta_revision_test', 'update 8 number 3', 'update 7 number 3' );
+
+                // Restore the previous revision.
+                $revisions     = wp_get_post_revisions( $post_id );
+                $last_revision = array_shift( $revisions );
+                wp_restore_post_revision( $last_revision->ID );
+
+                /*
+                 * Verify that multiple metas stored correctly.
+                 */
+                $this->assertEquals( array( 'update 7', 'update 7 number 2', 'update 7 number 3' ), get_post_meta( $post_id, 'meta_revision_test' ) );
+
+                /*
+                 * Test the revisioning of a multidimensional array.
+                 */
+                $test_array = array(
+                        'a' => array(
+                                '1',
+                                '2',
+                                '3',
+                        ),
+                        'b' => 'ok',
+                        'c' => array(
+                                'multi' => array(
+                                        'a',
+                                        'b',
+                                        'c',
+                                ),
+                                'not'   => 'ok',
+                        ),
+                );
+
+                // Clear any old value.
+                delete_post_meta( $post_id, 'meta_revision_test' );
+
+                // Set the test meta to the array.
+                update_post_meta( $post_id, 'meta_revision_test', $test_array );
+
+                // Update to save.
+                wp_update_post( array( 'ID' => $post_id ) );
+
+                // Set the test meta blank.
+                update_post_meta( $post_id, 'meta_revision_test', '' );
+
+                // Restore the previous revision.
+                $revisions     = wp_get_post_revisions( $post_id );
+                $last_revision = array_shift( $revisions );
+                wp_restore_post_revision( $last_revision->ID );
+
+                /*
+                 * Verify  multidimensional array stored correctly.
+                 */
+                $stored_array = get_post_meta( $post_id, 'meta_revision_test' );
+                $this->assertEquals( $test_array, $stored_array[0] );
+                /*
+
+                 * Test multiple revisions on the same key.
+                 */
+
+                // Set the test meta to the array.
+                add_post_meta( $post_id, 'meta_multiples_test', 'test1' );
+                add_post_meta( $post_id, 'meta_multiples_test', 'test2' );
+                add_post_meta( $post_id, 'meta_multiples_test', 'test3' );
+
+                // Update to save.
+                wp_update_post( array( 'ID' => $post_id ) );
+
+                $stored_array = get_post_meta( $post_id, 'meta_multiples_test' );
+                $expect       = array( 'test1', 'test2', 'test3' );
+
+                $this->assertEquals( $expect, $stored_array );
+
+                // Restore the previous revision.
+                $revisions     = wp_get_post_revisions( $post_id );
+                $last_revision = array_shift( $revisions );
+                wp_restore_post_revision( $last_revision->ID );
+
+                $stored_array = get_post_meta( $post_id, 'meta_multiples_test' );
+                $expect       = array( 'test1', 'test2', 'test3' );
+
+                $this->assertEquals( $expect, $stored_array );
+
+                // Cleanup!
+                wp_delete_post( $original_post_id );
+        }
+
+        /**
+         * Verify that only existing meta is revisioned.
+         */
+        public function only_existing_meta_is_revisioned() {
+                add_filter( 'wp_post_revision_meta_keys', array( $this, 'add_revisioned_keys' ) );
+
+                // Set up a new post.
+                $post_id = $this->factory->post->create(
+                        array(
+                                'post_content' => 'initial content',
+                        )
+                );
+
+                // Revision v1.
+                wp_update_post(
+                        array(
+                                'ID'           => $post_id,
+                                'post_content' => 'updated content v1',
+                        )
+                );
+
+                $this->assertPostNotHasMetaKey( $post_id, 'foo' );
+                $this->assertPostNotHasMetaKey( $post_id, 'bar' );
+
+                $revisions = wp_get_post_revisions( $post_id );
+                $revision  = array_shift( $revisions );
+                $this->assertEmpty( get_metadata( 'post', $revision->ID ) );
+
+                // Revision v2.
+                wp_update_post(
+                        array(
+                                'ID'           => $post_id,
+                                'post_content' => 'updated content v2',
+                                'meta_input'   => array(
+                                        'foo' => 'foo v2',
+                                ),
+                        )
+                );
+
+                $this->assertPostHasMetaKey( $post_id, 'foo' );
+                $this->assertPostNotHasMetaKey( $post_id, 'bar' );
+                $this->assertPostNotHasMetaKey( $post_id, 'meta_revision_test' );
+
+                $revisions = wp_get_post_revisions( $post_id );
+                $revision  = array_shift( $revisions );
+                $this->assertPostHasMetaKey( $revision->ID, 'foo' );
+                $this->assertPostNotHasMetaKey( $revision->ID, 'bar' );
+                $this->assertPostNotHasMetaKey( $revision->ID, 'meta_revision_test' );
+        }
+
+        /**
+         * Verify that blank strings are revisioned correctly.
+         */
+        public function blank_meta_is_revisioned() {
+
+                add_filter( 'wp_post_revision_meta_keys', array( $this, 'add_revisioned_keys' ) );
+
+                // Set up a new post.
+                $post_id = $this->factory->post->create(
+                        array(
+                                'post_content' => 'initial content',
+                                'meta_input'   => array(
+                                        'foo' => 'foo',
+                                ),
+                        )
+                );
+
+                // Set the test meta to an empty string.
+                update_post_meta( $post_id, 'foo', '' );
+
+                // Update to save.
+                wp_update_post( array( 'ID' => $post_id ) );
+
+                $stored_array = get_post_meta( $post_id, 'meta_multiples_test' );
+                $expect       = array( 'test1', 'test2', 'test3' );
+
+                $this->assertEquals( $expect, $stored_array );
+
+                // Restore the previous revision.
+                $revisions     = wp_get_post_revisions( $post_id );
+                $last_revision = array_shift( $revisions );
+                wp_restore_post_revision( $last_revision->ID );
+                $stored_data = get_post_meta( $post_id, 'foo' );
+                $this->assertEquals( '', $stored_data[0] );
+        }
+
+
+        /**
+         * @dataProvider data_register_post_meta_supports_revisions
+         */
+        public function test_register_post_meta_supports_revisions( $post_type, $meta_key, $args, $expected_is_revisioned ) {
+                register_post_meta( $post_type, $meta_key, $args );
+
+                // Set up a new post.
+                $post_id = $this->factory->post->create(
+                        array(
+                                'post_content' => 'initial content',
+                                'post_type'    => $post_type,
+                                'meta_input'   => array(
+                                        $meta_key => 'foo',
+                                ),
+                        )
+                );
+
+                // Update the post meta and post to save.
+                update_post_meta( $post_id, $meta_key, 'bar' );
+                wp_update_post(
+                        array(
+                                'ID'         => $post_id,
+                                'post_title' => 'updated title',
+                        )
+                );
+
+                // Check the last revision for the post to see if the meta key was revisioned
+                $revisions       = wp_get_post_revisions( $post_id );
+                $revision        = array_shift( $revisions );
+                $revisioned_meta = get_post_meta( $revision->ID, $meta_key, true );
+                $this->assertEquals( $expected_is_revisioned, 'bar' === $revisioned_meta );
+
+                // Reset global so subsequent data tests do not get polluted.
+                $GLOBALS['wp_meta_keys'] = array();
+        }
+
+        public function data_register_post_meta_supports_revisions() {
+                return array(
+                        array( 'post', 'registered_key1', array( 'single' => true ), false ),
+                        array(
+                                'post',
+                                'registered_key1',
+                                array(
+                                        'single'            => true,
+                                        'revisions_enabled' => true,
+                                ),
+                                true,
+                        ),
+                        array( 'page', 'registered_key2', array( 'revisions_enabled' => false ), false ),
+                        array( 'page', 'registered_key2', array( 'revisions_enabled' => true ), true ),
+                        array( '', 'registered_key3', array( 'revisions_enabled' => false ), false ),
+                        array( '', 'registered_key3', array( 'revisions_enabled' => true ), true ),
+                );
+        }
+
+        /**
+         * Assert the a post has a meta key.
+         *
+         * @param int    $post_id        The ID of the post to check.
+         * @param string $meta_key The meta key to check for.
+         */
+        protected function assertPostHasMetaKey( $post_id, $meta_key ) {
+                $this->assertArrayHasKey( $meta_key, get_metadata( 'post', $post_id ) );
+        }
+
+        /**
+         * Assert that post does not have a meta key.
+         *
+         * @param int    $post_id        The ID of the post to check.
+         * @param string $meta_key The meta key to check for.
+         */
+        protected function assertPostNotHasMetaKey( $post_id, $meta_key ) {
+                $this->assertArrayNotHasKey( $meta_key, get_metadata( 'post', $post_id ) );
+        }
+
+        /**
+         * Test post meta revisioning with a custom post type, as well as the "page" post type.
+         *
+         * @dataProvider page_post_type_data_provider
+         */
+        public function test_revisions_stores_meta_values_page_and_cpt( $passed, $expected, $post_type, $supports_revisions = false ) {
+
+                // If the post type doesn't exist, create it, potentially supporting revisions.
+                if ( ! post_type_exists( $post_type ) ) {
+                        register_post_type(
+                                $post_type,
+                                array(
+                                        'public'   => true,
+                                        'supports' => $supports_revisions ? array( 'revisions' ) : array(),
+                                )
+                        );
+                }
+
+                // Create a test post.
+                $page_id = $this->factory->post->create(
+                        array(
+                                'post_type'    => $post_type,
+                                'post_content' => 'some initial content',
+                        )
+                );
+
+                // Add the revisioning filter.
+                add_filter( 'wp_post_revision_meta_keys', array( $this, 'add_revisioned_keys' ) );
+
+                // Test revisioning.
+                update_post_meta( $page_id, 'meta_revision_test', wp_slash( $passed ) );
+
+                // Update the post, storing a revision.
+                wp_update_post(
+                        array(
+                                'post_content' => 'some more content',
+                                'ID'           => $page_id,
+                        )
+                );
+
+                // Retrieve the created revision.
+                $revisions = (array) wp_get_post_revisions( $page_id );
+
+                if ( $expected ) {
+                        // Go back to load the previous revision.
+                        $last_revision = array_shift( $revisions );
+                                wp_restore_post_revision( $last_revision->ID );
+                        $this->assertEquals( $expected, get_post_meta( $page_id, 'meta_revision_test', true ) );
+                } else {
+                        $this->assertEmpty( $revisions );
+                }
+        }
+
+        /**
+         * Provide data for the page post type tests.
+         */
+        public function page_post_type_data_provider() {
+                return array(
+                        array(
+                                'Test string',
+                                'Test string',
+                                'page',
+                        ),
+                        array(
+                                'Test string',
+                                false,
+                                'custom_type',
+                        ),
+                        array(
+                                'Test string',
+                                'Test string',
+                                'custom_type',
+                                true,
+                        ),
+                );
+        }
+}

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

@@ -215 +215 @@
                         'author',
                         'date',
                         'date_gmt',
+                        'id',
+                        'meta',
                         'modified',
                         'modified_gmt',
-                        'guid',
-                        'id',
                         'parent',
                         'slug',
+                        'guid',
                         'title',
                         'excerpt',
                         'content',
@@ -288 +289 @@
                 $response   = rest_get_server()->dispatch( $request );
                 $data       = $response->get_data();
                 $properties = $data['schema']['properties'];
-                $this->assertCount( 13, $properties );
+                $this->assertCount( 14, $properties );
                 $this->assertArrayHasKey( 'author', $properties );
                 $this->assertArrayHasKey( 'content', $properties );
                 $this->assertArrayHasKey( 'date', $properties );
@@ -302 +303 @@
                 $this->assertArrayHasKey( 'slug', $properties );
                 $this->assertArrayHasKey( 'title', $properties );
                 $this->assertArrayHasKey( 'preview_link', $properties );
+                $this->assertArrayHasKey( 'meta', $properties );
         }
 
         public function test_create_item() {

tests/phpunit/tests/rest-api/rest-global-styles-revisions-controller.php

@@ -132 +132 @@
                         ),
                 );
 
-                wp_update_post( $new_styles_post, true, false );
+                wp_update_post( $new_styles_post, true );
 
                 $new_styles_post = array(
                         'ID'           => self::$global_styles_id,
@@ -162 +162 @@
                         ),
                 );
 
-                wp_update_post( $new_styles_post, true, false );
+                wp_update_post( $new_styles_post, true );
 
                 $new_styles_post = array(
                         'ID'           => self::$global_styles_id,
@@ -192 +192 @@
                         ),
                 );
 
-                wp_update_post( $new_styles_post, true, false );
+                wp_update_post( $new_styles_post, true );
                 wp_set_current_user( 0 );
         }
 
@@ -326 +326 @@
                         'post_content' => wp_json_encode( $config ),
                 );
 
-                wp_update_post( $updated_styles_post, true, false );
+                wp_update_post( $updated_styles_post, true );
 
                 $request  = new WP_REST_Request( 'GET', '/wp/v2/global-styles/' . self::$global_styles_id . '/revisions' );
                 $response = rest_get_server()->dispatch( $request );

tests/phpunit/tests/rest-api/rest-post-meta-fields.php

@@ -17 +17 @@
                         'cpt',
                         array(
                                 'show_in_rest' => true,
-                                'supports'     => array( 'custom-fields' ),
+                                'supports'     => array( 'custom-fields', 'revisions' ),
                         )
                 );
 
@@ -157 +157 @@
                         'cpt',
                         array(
                                 'show_in_rest' => true,
-                                'supports'     => array( 'custom-fields' ),
+                                'supports'     => array( 'custom-fields', 'revisions' ),
                         )
                 );
 
@@ -1376 +1376 @@
          * @dataProvider data_update_value_return_success_with_same_value
          */
         public function test_update_value_return_success_with_same_value( $meta_key, $meta_value ) {
-                add_post_meta( self::$post_id, $meta_key, $meta_value );
-
                 $this->grant_write_permission();
 
                 $data = array(
@@ -1392 +1390 @@
                 $response = rest_get_server()->dispatch( $request );
 
                 $this->assertSame( 200, $response->get_status() );
+
+                // Verify the returned meta value is correct.
+                $data = $response->get_data();
+                $this->assertArrayHasKey( 'meta', $data );
+                $this->assertArrayHasKey( $meta_key, $data['meta'] );
+                $this->assertSame( $meta_value, $data['meta'][ $meta_key ] );
+
         }
 
         public function data_update_value_return_success_with_same_value() {
@@ -3112 +3117 @@
                 }
                 return $query;
         }
+
+
+        /**
+         * Test that single post meta is revisioned when saving to the posts REST API endpoint.
+         *
+         * @ticket 20564
+         */
+        public function test_revisioned_single_post_meta_with_posts_endpoint() {
+                $this->grant_write_permission();
+
+                register_post_meta(
+                        'post',
+                        'foo',
+                        array(
+                                'single'            => true,
+                                'show_in_rest'      => true,
+                                'revisions_enabled' => true,
+                        )
+                );
+
+                $post_id = self::$post_id;
+
+                // Update the post, saving the meta.
+                $request = new WP_REST_Request( 'PUT', sprintf( '/wp/v2/posts/%d', $post_id ) );
+                $request->set_body_params(
+                        array(
+                                'title' => 'Revision 1',
+                                'meta'  => array(
+                                        'foo' => 'bar',
+                                ),
+                        )
+                );
+                $response = rest_get_server()->dispatch( $request );
+                $this->assertSame( 200, $response->get_status() );
+
+                // Get the last revision.
+                $revisions   = wp_get_post_revisions( $post_id, array( 'posts_per_page' => 1 ) );
+                $revision_id = array_shift( $revisions )->ID;
+
+                // @todo Ensure the revisions endpoint returns the correct meta values
+                // Check that the revisions endpoint returns the correct meta value.
+                $request  = new WP_REST_Request( 'GET', sprintf( '/wp/v2/posts/%d/revisions/%d', $post_id, $revision_id ) );
+                $response = rest_get_server()->dispatch( $request );
+                $this->assertSame( 200, $response->get_status() );
+                $data = $response->get_data();
+                $this->assertSame( 'bar', $response->get_data()['meta']['foo'] );
+
+                // Check that the post meta is set correctly.
+                $this->assertSame( 'bar', get_post_meta( $revision_id, 'foo', true ) );
+
+                // Create two more revisions with different meta values for the foo key.
+                $request = new WP_REST_Request( 'PUT', sprintf( '/wp/v2/posts/%d', $post_id ) );
+                $request->set_body_params(
+                        array(
+                                'title' => 'Revision 2',
+                                'meta'  => array(
+                                        'foo' => 'baz',
+                                ),
+                        )
+                );
+                $response = rest_get_server()->dispatch( $request );
+                $this->assertSame( 200, $response->get_status() );
+
+                // Get the last revision.
+                $revisions     = wp_get_post_revisions( $post_id, array( 'posts_per_page' => 1 ) );
+                $revision_id_2 = array_shift( $revisions )->ID;
+
+                // Check that the revision has the correct meta value.
+                $request  = new WP_REST_Request( 'GET', sprintf( '/wp/v2/posts/%d/revisions/%d', $post_id, $revision_id_2 ) );
+                $response = rest_get_server()->dispatch( $request );
+                $this->assertSame( 200, $response->get_status() );
+                $this->assertSame( 'baz', $response->get_data()['meta']['foo'] );
+
+                // Check that the post meta is set correctly.
+                $this->assertSame( 'baz', get_post_meta( $revision_id_2, 'foo', true ) );
+
+                // One more revision!
+                $request = new WP_REST_Request( 'PUT', sprintf( '/wp/v2/posts/%d', $post_id ) );
+                $request->set_body_params(
+                        array(
+                                'title' => 'Revision 3',
+                                'meta'  => array(
+                                        'foo' => 'qux',
+                                ),
+                        )
+                );
+                $response = rest_get_server()->dispatch( $request );
+                $this->assertSame( 200, $response->get_status() );
+
+                // Get the last revision.
+                $revisions     = wp_get_post_revisions( $post_id, array( 'posts_per_page' => 1 ) );
+                $revision_id_3 = array_shift( $revisions )->ID;
+
+                // Check that the revision has the correct meta value.
+                $request  = new WP_REST_Request( 'GET', sprintf( '/wp/v2/posts/%d/revisions/%d', $post_id, $revision_id_3 ) );
+                $response = rest_get_server()->dispatch( $request );
+                $this->assertSame( 200, $response->get_status() );
+                $this->assertSame( 'qux', $response->get_data()['meta']['foo'] );
+
+                // Check that the post meta is set correctly.
+                $this->assertSame( 'qux', get_post_meta( $revision_id_3, 'foo', true ) );
+
+                // Restore Revision 3 and verify the post gets the correct meta value.
+                wp_restore_post_revision( $revision_id_3 );
+                $this->assertSame( 'qux', get_post_meta( $post_id, 'foo', true ) );
+
+                // Restore Revision 2 and verify the post gets the correct meta value.
+                wp_restore_post_revision( $revision_id_2 );
+                $this->assertSame( 'baz', get_post_meta( $post_id, 'foo', true ) );
+        }
+
+        /**
+         * Test that multi-post meta is revisioned when saving to the posts REST API endpoint.
+         *
+         * @ticket 20564
+         */
+        public function test_revisioned_multiple_post_meta_with_posts_endpoint() {
+                $this->grant_write_permission();
+
+                register_post_meta(
+                        'post',
+                        'foo',
+                        array(
+                                'single'            => false,
+                                'show_in_rest'      => true,
+                                'revisions_enabled' => true,
+                        )
+                );
+
+                $post_id = self::$post_id;
+
+                $request = new WP_REST_Request( 'PUT', sprintf( '/wp/v2/posts/%d', $post_id ) );
+                $request->set_body_params(
+                        array(
+                                'title' => 'Revision 1',
+                                'meta'  => array(
+                                        'foo' => array(
+                                                'bar',
+                                                'bat',
+                                                'baz',
+                                        ),
+                                ),
+                        )
+                );
+                $response = rest_get_server()->dispatch( $request );
+                $this->assertSame( 200, $response->get_status() );
+
+                // Log the current post meta.
+                $meta = get_post_meta( $post_id );
+
+                // Update the post.
+                $request = new WP_REST_Request( 'PUT', sprintf( '/wp/v2/posts/%d', $post_id ) );
+                $request->set_body_params(
+                        array(
+                                'title' => 'Revision 1 update',
+                        )
+                );
+                $response = rest_get_server()->dispatch( $request );
+                $this->assertSame( 200, $response->get_status() );
+
+                // Get the last revision.
+                $revisions     = wp_get_post_revisions( $post_id, array( 'posts_per_page' => 1 ) );
+                $revision_id_1 = array_shift( $revisions )->ID;
+
+                // Check that the revision has the correct meta value.
+                $request  = new WP_REST_Request( 'GET', sprintf( '/wp/v2/posts/%d/revisions/%d', $post_id, $revision_id_1 ) );
+                $response = rest_get_server()->dispatch( $request );
+                $this->assertSame( 200, $response->get_status() );
+
+                $this->assertSame(
+                        array( 'bar', 'bat', 'baz' ),
+                        $response->get_data()['meta']['foo']
+                );
+                $this->assertSame(
+                        array( 'bar', 'bat', 'baz' ),
+                        get_post_meta( $revision_id_1, 'foo' )
+                );
+
+                $request = new WP_REST_Request( 'PUT', sprintf( '/wp/v2/posts/%d', $post_id ) );
+                $request->set_body_params(
+                        array(
+                                'title' => 'Revision 2',
+                                'meta'  => array(
+                                        'foo' => array(
+                                                'car',
+                                                'cat',
+                                        ),
+                                ),
+                        )
+                );
+                $response = rest_get_server()->dispatch( $request );
+                $this->assertSame( 200, $response->get_status() );
+
+                // Get the last revision.
+                $revisions     = wp_get_post_revisions( $post_id, array( 'posts_per_page' => 1 ) );
+                $revision_id_2 = array_shift( $revisions )->ID;
+
+                // Check that the revision has the correct meta value.
+                $request  = new WP_REST_Request( 'GET', sprintf( '/wp/v2/posts/%d/revisions/%d', $post_id, $revision_id_2 ) );
+                $response = rest_get_server()->dispatch( $request );
+                $this->assertSame( 200, $response->get_status() );
+
+                $this->assertSame(
+                        array( 'car', 'cat' ),
+                        $response->get_data()['meta']['foo']
+                );
+                $this->assertSame( array( 'car', 'cat' ), get_post_meta( $revision_id_2, 'foo' ) );
+
+                $request = new WP_REST_Request( 'PUT', sprintf( '/wp/v2/posts/%d', $post_id ) );
+                $request->set_body_params(
+                        array(
+                                'title' => 'Revision 3',
+                                'meta'  => array(
+                                        'foo' => null,
+                                ),
+                        )
+                );
+                $response = rest_get_server()->dispatch( $request );
+                $this->assertSame( 200, $response->get_status() );
+
+                // Get the last revision.
+                $revisions     = wp_get_post_revisions( $post_id, array( 'posts_per_page' => 1 ) );
+                $revision_id_3 = array_shift( $revisions )->ID;
+
+                // Check that the revision has the correct meta value.
+                $request  = new WP_REST_Request( 'GET', sprintf( '/wp/v2/posts/%d/revisions/%d', $post_id, $revision_id_3 ) );
+                $response = rest_get_server()->dispatch( $request );
+                $this->assertSame( 200, $response->get_status() );
+
+                $this->assertSame(
+                        array(),
+                        $response->get_data()['meta']['foo']
+                );
+                $this->assertSame( array(), get_post_meta( $revision_id_3, 'foo' ) );
+
+                // Restore Revision 3 and verify the post gets the correct meta value.
+                wp_restore_post_revision( $revision_id_3 );
+                $this->assertSame( array(), get_post_meta( $post_id, 'foo' ) );
+
+                // Restore Revision 2 and verify the post gets the correct meta value.
+                wp_restore_post_revision( $revision_id_2 );
+                $this->assertSame( array( 'car', 'cat' ), get_post_meta( $post_id, 'foo' ) );
+        }
+
+        /**
+         * Test post meta revisions with a custom post type and the page post type.
+         *
+         * @group revision
+         * @dataProvider test_revisioned_single_post_meta_with_posts_endpoint_page_and_cpt_data_provider
+         */
+        public function test_revisioned_single_post_meta_with_posts_endpoint_page_and_cpt( $passed, $expected, $post_type ) {
+
+                $this->grant_write_permission();
+
+                // Create the custom meta.
+                register_post_meta(
+                        $post_type,
+                        'foo',
+                        array(
+                                'show_in_rest'      => true,
+                                'revisions_enabled' => true,
+                                'single'            => true,
+                                'type'              => 'string',
+                        )
+                );
+
+                // Set up a new post.
+                $post_id = $this->factory->post->create(
+                        array(
+                                'post_content' => 'initial content',
+                                'post_type'    => $post_type,
+                                'meta_input'   => array(
+                                        'foo' => 'foo',
+                                ),
+                        )
+                );
+
+                $plural_mapping = array(
+                        'page' => 'pages',
+                        'cpt'  => 'cpt',
+                );
+                $request        = new WP_REST_Request( 'GET', sprintf( '/wp/v2/%s', $plural_mapping[ $post_type ] ) );
+
+                $response = rest_get_server()->dispatch( $request );
+
+                $request = new WP_REST_Request( 'POST', sprintf( '/wp/v2/%s/%d', $plural_mapping[ $post_type ], $post_id ) );
+                $request->set_body_params(
+                        array(
+                                'title' => 'Revision 1',
+                                'meta'  => array(
+                                        'foo' => $passed,
+                                ),
+                        )
+                );
+
+                $response = rest_get_server()->dispatch( $request );
+                $this->assertSame( 200, $response->get_status() );
+
+                // Update the post.
+                $request = new WP_REST_Request( 'POST', sprintf( '/wp/v2/%s/%d', $plural_mapping[ $post_type ], $post_id ) );
+                $request->set_body_params(
+                        array(
+                                'title' => 'Revision 1 update',
+                        )
+                );
+                $response = rest_get_server()->dispatch( $request );
+                $this->assertSame( 200, $response->get_status() );
+
+                // Get the last revision.
+                $revisions = wp_get_post_revisions( $post_id, array( 'posts_per_page' => 1 ) );
+
+                $revision_id_1 = array_shift( $revisions )->ID;
+
+                // Check that the revision has the correct meta value.
+                $request  = new WP_REST_Request( 'GET', sprintf( '/wp/v2/%s/%d/revisions/%d', $plural_mapping[ $post_type ], $post_id, $revision_id_1 ) );
+                $response = rest_get_server()->dispatch( $request );
+                $this->assertSame( 200, $response->get_status() );
+
+                $this->assertSame(
+                        $passed,
+                        $response->get_data()['meta']['foo']
+                );
+
+                $this->assertSame(
+                        array( $passed ),
+                        get_post_meta( $revision_id_1, 'foo' )
+                );
+
+                unregister_post_meta( $post_type, 'foo' );
+                wp_delete_post( $post_id, true );
+        }
+
+        /**
+         * Provide data for the meta revision checks.
+         */
+        public function test_revisioned_single_post_meta_with_posts_endpoint_page_and_cpt_data_provider() {
+                return array(
+                        array(
+                                'Test string',
+                                'Test string',
+                                'cpt',
+                        ),
+                        array(
+                                'Test string',
+                                'Test string',
+                                'page',
+                        ),
+                        array(
+                                'Test string',
+                                false,
+                                'cpt',
+                        ),
+
+                );
+        }
 }

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

@@ -179 +179 @@
                         'modified_gmt',
                         'guid',
                         'id',
+                        'meta',
                         'parent',
                         'slug',
                         'title',
@@ -335 +336 @@
                 $response   = rest_get_server()->dispatch( $request );
                 $data       = $response->get_data();
                 $properties = $data['schema']['properties'];
-                $this->assertCount( 12, $properties );
+                $this->assertCount( 13, $properties );
                 $this->assertArrayHasKey( 'author', $properties );
                 $this->assertArrayHasKey( 'content', $properties );
                 $this->assertArrayHasKey( 'date', $properties );
@@ -348 +349 @@
                 $this->assertArrayHasKey( 'parent', $properties );
                 $this->assertArrayHasKey( 'slug', $properties );
                 $this->assertArrayHasKey( 'title', $properties );
+                $this->assertArrayHasKey( 'meta', $properties );
         }
 
         public function test_create_item() {

tests/phpunit/tests/user/wpRegisterPersistedPreferencesMeta.php

@@ -52 +52 @@
                                                 'additionalProperties' => true,
                                         ),
                                 ),
+                                'revisions_enabled' => false,
                         ),
                         $wp_meta_keys['user'][''][ $meta_key ],
                         'The registered metadata did not have the expected structure'

tests/qunit/fixtures/wp-api-generated.js

@@ -11417 +11417 @@
         "excerpt": {
             "rendered": ""
         },
+        "meta": {
+            "meta_key": ""
+        },
         "_links": {
             "parent": [
                 {
@@ -11446 +11449 @@
         "excerpt": {
             "rendered": "<p>REST API Client Fixture: Post</p>\n"
         },
+        "meta": {
+            "meta_key": ""
+        },
         "_links": {
             "parent": [
                 {
@@ -11476 +11482 @@
     },
     "excerpt": {
         "rendered": "<p>REST API Client Fixture: Post</p>\n"
+    },
+    "meta": {
+        "meta_key": ""
     }
 };
 
@@ -11501 +11510 @@
         "excerpt": {
             "rendered": ""
         },
+        "meta": {
+            "meta_key": ""
+        },
         "_links": {
             "parent": [
                 {
@@ -11531 +11543 @@
     },
     "excerpt": {
         "rendered": ""
+    },
+    "meta": {
+        "meta_key": ""
     }
 };
 
@@ -11677 +11692 @@
         "excerpt": {
             "rendered": ""
         },
+        "meta": {
+            "meta_key": ""
+        },
         "_links": {
             "parent": [
                 {
@@ -11706 +11724 @@
         "excerpt": {
             "rendered": "<p>REST API Client Fixture: Page</p>\n"
         },
+        "meta": {
+            "meta_key": ""
+        },
         "_links": {
             "parent": [
                 {
@@ -11736 +11757 @@
     },
     "excerpt": {
         "rendered": "<p>REST API Client Fixture: Page</p>\n"
+    },
+    "meta": {
+        "meta_key": ""
     }
 };
 
@@ -11761 +11785 @@
         "excerpt": {
             "rendered": ""
         },
+        "meta": {
+            "meta_key": ""
+        },
         "_links": {
             "parent": [
                 {
@@ -11791 +11818 @@
     },
     "excerpt": {
         "rendered": ""
+    },
+    "meta": {
+        "meta_key": ""
     }
 };