From c588bdd2d4cc0c05a80546f187693f94c71ca984 Mon Sep 17 00:00:00 2001
From: Gary Pendergast <gary@pento.net>
Date: Thu, 26 Oct 2017 11:38:05 +1100
Subject: [PATCH] Don't show the classic editor dropdown on unsupported post
 types. (#3146)

Also adds a new `gutenberg_can_edit_post_type` filter, so plugins can disable Gutenberg by post type.
---
 gutenberg.php    | 19 ++++++-----------
 lib/register.php | 53 +++++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 52 insertions(+), 20 deletions(-)

diff --git a/gutenberg.php b/gutenberg.php
index 3a93cfd2c91103..0ed4d2c47f6894 100644
--- a/gutenberg.php
+++ b/gutenberg.php
@@ -136,18 +136,7 @@ function gutenberg_init( $return, $post ) {
 		return false;
 	}
 
-	$post_type        = $post->post_type;
-	$post_type_object = get_post_type_object( $post_type );
-
-	if ( 'attachment' === $post_type ) {
-		return false;
-	}
-
-	if ( ! $post_type_object->show_in_rest ) {
-		return false;
-	}
-
-	if ( ! post_type_supports( $post_type, 'editor' ) ) {
+	if ( ! gutenberg_can_edit_post( $post ) ) {
 		return false;
 	}
 
@@ -349,7 +338,7 @@ function gutenberg_add_edit_link_filters() {
  * @return array          Updated post actions.
  */
 function gutenberg_add_edit_link( $actions, $post ) {
-	if ( 'trash' === $post->post_status || ! post_type_supports( $post->post_type, 'editor' ) ) {
+	if ( ! gutenberg_can_edit_post( $post ) ) {
 		return $actions;
 	}
 
@@ -420,6 +409,10 @@ function gutenberg_modify_add_new_button_url( $url, $path ) {
  * @since 1.5.0
  */
 function gutenberg_replace_default_add_new_button() {
+	global $typenow;
+	if ( ! gutenberg_can_edit_post_type( $typenow ) ) {
+		return;
+	}
 	?>
 	<style type="text/css">
 		.split-page-title-action {
diff --git a/lib/register.php b/lib/register.php
index a9d995bbb32a88..0b145103523cf4 100644
--- a/lib/register.php
+++ b/lib/register.php
@@ -248,26 +248,65 @@ function gutenberg_collect_meta_box_data() {
 /**
  * Return whether the post can be edited in Gutenberg and by the current user.
  *
- * Gutenberg depends on the REST API, and if the post type is not shown in the
- * REST API, then the post cannot be edited in Gutenberg.
- *
  * @since 0.5.0
  *
- * @param int $post_id Post.
+ * @param int|WP_Post $post_id Post.
  * @return bool Whether the post can be edited with Gutenberg.
  */
 function gutenberg_can_edit_post( $post_id ) {
 	$post = get_post( $post_id );
-	if ( ! $post || ! post_type_exists( $post->post_type ) ) {
+	if ( ! $post ) {
 		return false;
 	}
-	$post_type_object = get_post_type_object( $post->post_type );
-	if ( ! $post_type_object->show_in_rest ) {
+
+	if ( 'trash' === $post->post_status ) {
+		return false;
+	}
+
+	if ( ! gutenberg_can_edit_post_type( $post->post_type ) ) {
 		return false;
 	}
+
 	return current_user_can( 'edit_post', $post_id );
 }
 
+/**
+ * Return whether the post type can be edited in Gutenberg.
+ *
+ * Gutenberg depends on the REST API, and if the post type is not shown in the
+ * REST API, then the post cannot be edited in Gutenberg.
+ *
+ * @since 1.5.2
+ *
+ * @param string $post_type The post type.
+ * @return bool Wehther the post type can be edited with Gutenberg.
+ */
+function gutenberg_can_edit_post_type( $post_type ) {
+	$can_edit = true;
+	if ( ! post_type_exists( $post_type ) ) {
+		$can_edit = false;
+	}
+
+	if ( ! post_type_supports( $post_type, 'editor' ) ) {
+		$can_edit = false;
+	}
+
+	$post_type_object = get_post_type_object( $post_type );
+	if ( ! $post_type_object->show_in_rest ) {
+		$can_edit = false;
+	}
+
+	/**
+	 * Filter to allow plugins to enable/disable Gutenberg for particular post types.
+	 *
+	 * @since 1.5.2
+	 *
+	 * @param bool   $can_edit  Whether the post type can be edited or not.
+	 * @param string $post_type The post type being checked.
+	 */
+	return apply_filters( 'gutenberg_can_edit_post_type', $can_edit, $post_type );
+}
+
 /**
  * Determine whether a post has blocks.
  *