Classic Text block fails to preview if ACF is installed

[nylen]

Using a fresh install of WP 4.9 and Gutenberg 1.7.0 with the Advanced Custom Fields plugin activated (version 4.4.12), upon inserting a Classic Text block, the block cannot be used or edited:

The following errors (including more attempts to download non-existent TinyMCE plugins) appear in the console:

Deactivating the ACF plugin resolves this issue as well as the failed requests for TinyMCE plugins.

[BoardJames]

@ephox-mogran and I spent some time trying to figure out what is going wrong.

The error message is being caused by the theme failing to load. The theme and plugins are failing to load because TinyMCE is trying to get it from wp-content/plugins/gutenberg/vendor when it should be loading them from wp-includes/js/tinymce. This seems to be happening because the global tinyMCE.baseURL is being overwritten when gutenberg loads.

So I think the following is happening:

1. Wordpress TinyMCE is loaded with the base url wp-includes/js/tinymce
2. Gutenberg TinyMCE is loaded with the base url wp-content/plugins/gutenberg/vendor which overwrites the global tinyMCE.baseURL
3. Wordpress TinyMCE tries to load plugins (possibly ACF requests a TinyMCE instance?) and uses the global tinyMCE.baseURL which looks for them in wp-content/plugins/gutenberg/vendor and fails
4. The vendored plugin files load so the plugins are made available
5. Gutenberg editors load and since the vendored plugins register themselves it doesn't matter that the baseUrl is wrong because it never has to look for them.

[youknowriad]

Is it time to rely on the same version for classic and gutenberg editor @iseulde ?

[nylen]

possibly ACF requests a TinyMCE instance?

Probably so, this type of issue is one reason why we initially chose to render metaboxes within iframes.

Not saying that was the right solution, just providing context.

[youknowriad]

Fixed by #6848