Produce warning when permalinks are not enabled

[bobbingwide]

Issue Overview

When permalinks are not set things don't work properly. Gutenberg should be up front about this.

Steps to Reproduce (for bugs)

1. As for withAPIData URL parameters and Plain Permalinks #3215 .

Expected Behavior

Gutenberg should let the user know that there could be a problem when a permalink structure is not defined.

Current Behavior

Unexpected messages in the browser log. Things not working as expected. No warnings that things might not work.

Possible Solution

Call this logic at the end of gutenberg_pre_init

/**
 * Verifies permalinks are set
 *
 * @since 2.0.1
 */
function gutenberg_check_permalinks() {

	if ( is_multisite() ) {
		if ( get_blog_option( null, 'permalink_structure' ) ) {	
			return;
		}
	} elseif ( get_option( 'permalink_structure' ) ) {
		return;
	}
	add_action( 'admin_notices', 'gutenberg_permalink_notice' );
}

/**
 * Issues a notice about permalinks
 */
function gutenberg_permalink_notice() {
	echo '<div class="error"><p>';
	echo __( 'Gutenberg works better with permalinks.', 'gutenberg' );
	echo '</p></div>';
}

Obviously the wording will need some tweaking. And the logic won't be necessary once WordPress TRAC 42382 has been delivered.

Screenshots / Video

Related Issues and/or PRs

#3215. Possibly #2704 and #2596. And, to be investigated, problems with reusable blocks.

Todos

• Tests
• Documentation

[danielbachhuber]

@bobbingwide Gutenberg should work without pretty permalinks enabled. What specific issues have you run into?

[bobbingwide]

@danielbachhuber regarding permalinks specifically... #3215, which for me was responsible for the problem reported in #3210.

I also had problems with saved blocks but wasn't able to confirm if this was just a performance issue on my local machine when I had my server tracing enabled. Additionally, I may have inadvertently overridden the registration of the wp_block post type accidentally turning off 'show_in_rest'.

The point is that anyone who fires up a brand new install to try Gutenberg may start trying to use it without having selected something other than plain permalinks.

[danielbachhuber]

Ah, I should've clicked through on #3215 before I created the new issue. #3215 is the appropriate issue to fix.