Remove PHP code merged into WordPress 5.0

[youknowriad]

Important note: Closing this issue means we update the minimum WP supported version of the plugin to 5.0. (Edit: Done in #13370)

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Now that WordPress 5.0 is ready to be released, we need to start working on the next phase and ensure we don't duplicate code in the plugin.

Things that should be removed from the plugin:

• REST API endpoints and tweaks (Framework: Remove 5.0-merged REST API integrations #13408)
• Block parsing, rendering utilities (Plugin: Remove 5.0-merged block registration functions, integrations #13412)
• php files adding the MetaBoxes support (Plugin: Deprecate metabox supports, fall back to core #13449)
• Miscellaneous core compatibility (lib/compat.php) (Plugin: Remove redundant core compatibility from plugin #13442)
• Bootstrapping the Gutenberg editor (already done in Core) (Plugin: Remove replace_editor filter, extend core editor #13569)

See Project: https://github.com/WordPress/gutenberg/projects/23

The php files that need to remain in the plugin are:

• Scripts registration (overriding)
• Dynamic blocks registration

[danielbachhuber]

Previously #10656

[swissspidy]

Related: #12559.

[aduth]

we update the minimum WP supported version of the plugin to 5.0.

Pull request: #13370

• REST API endpoints and tweaks

Pull request: #13408

• Block parsing, rendering utilities

Started on this one. Interestingly the wordpress_phpunit Docker image still uses WordPress 4.9.x , so naturally will encounter a fair number of fatal errors when trying to remove functions like register_block_type. Will definitely need to update this, but I'm not certain the process for doing so.

Edit: I guess my local Docker containers were very much out of date, and I'd wrongly relied on the install-docker.sh script to update them. Destroying it via docker-compose rm wordpress_phpunit and re-running the Docker install script seems to install the latest version as expected. I assume this isn't a problem for Travis, as the containers are created from scratch for each build?

Pull request: #13412

[aduth]

php files adding the MetaBoxes support

Pull request: #13449

Miscellaneous core compatibility (lib/compat.php)

Pull request: #13442

[aduth]

This is turning out to be a more significant effort.

Here's a project instead: https://github.com/WordPress/gutenberg/projects/23

[aduth]

Unless I've missed something, I'd now consider this effort concluded with the last major merge in #13569 (future deprecation removals notwithstanding).

https://github.com/WordPress/gutenberg/projects/23

[youknowriad]

Thanks Andrew, nice work here.