Allow disabling autosave post type support

src/wp-includes/class-wp-post-type.php

@@ -670,9 +670,20 @@ public function add_supports() {
 				}
 			}
 			unset( $this->supports );
+
+			/*
+			 * 'editor' support implies 'autosave' support for backward compatibility.
+			 * 'autosave' support needs to be explicitly removed if not desired.
+			 */
+			if (
+				post_type_supports( $this->name, 'editor' ) &&
+				! post_type_supports( $this->name, 'autosave' )
+			) {
+				add_post_type_support( $this->name, 'autosave' );
+			}
 		} elseif ( false !== $this->supports ) {
 			// Add default features.
-			add_post_type_support( $this->name, array( 'title', 'editor' ) );
+			add_post_type_support( $this->name, array( 'title', 'editor', 'autosave' ) );
 		}
 	}
 
@@ -922,6 +933,10 @@ public function get_autosave_rest_controller() {
 			return null;
 		}
 
+		if ( ! post_type_supports( $this->name, 'autosave' ) ) {
+			return null;
+		}
+
 		if ( 'attachment' === $this->name ) {
 			return null;
 		}

src/wp-includes/post.php

@@ -1705,7 +1705,8 @@ function get_post_types( $args = array(), $output = 'names', $operator = 'and' )
  *                                                         'editor', 'comments', 'revisions', 'trackbacks', 'author', 'excerpt',
  *                                                         'page-attributes', 'thumbnail', 'custom-fields', and 'post-formats'.
  *                                                         Additionally, the 'revisions' feature dictates whether the post type
- *                                                         will store revisions, and the 'comments' feature dictates whether the
+ *                                                         will store revisions, the 'autosave' feature dictates whether the post type
+ *                                                         will be autosaved, and the 'comments' feature dictates whether the
  *                                                         comments count will show on the edit screen. A feature can also be
  *                                                         specified as an array of arguments to provide additional information
  *                                                         about supporting that feature.
@@ -2184,7 +2185,8 @@ function _add_post_type_submenus() {
  * 'thumbnail', 'custom-fields', and 'post-formats'.
  *
  * Additionally, the 'revisions' feature dictates whether the post type will
- * store revisions, and the 'comments' feature dictates whether the comments
+ * store revisions, the 'autosave' feature dictates whether the post type
+ * will be autosaved, and the 'comments' feature dictates whether the comments
  * count will show on the edit screen.
  *
  * A third, optional parameter can also be passed along with a feature to provide