Site Editor: Adding 404 template causes rest_invalid_pattern

[Bernhard Reiter]

Reported and fixed by GH user @PatelUtkarsh at ​https://github.com/WordPress/gutenberg/pull/37579.

Quoting the Gutenberg PR:

Adding 404 template from /wp-admin/site-editor.php?postType=wp_template causes 400 with rest_invalid_pattern

• Theme without 404 templates.
• Open /wp-admin/site-editor.php?postType=wp_template
• Add new 404 templates.
• Used nightly WordPress build to test this.

Screencast: ​https://user-images.githubusercontent.com/5015489/147066116-2e23ff30-0dd7-45d3-a40a-510ef06156e2.mp4

Backport of ​https://github.com/WordPress/gutenberg/pull/37579. Props @PatelUtkarsh.

Quoting ​https://github.com/WordPress/gutenberg/pull/37579:

## Description
Adding 404 template from /wp-admin/site-editor.php?postType=wp_template causes 400 with rest_invalid_pattern

## How has this been tested?

• Theme without 404 templates.
• Open /wp-admin/site-editor.php?postType=wp_template
• Add new 404 templates.
• Used nightly WordPress build to test this.

## Screenshots
Bug:

​https://user-images.githubusercontent.com/5015489/147066116-2e23ff30-0dd7-45d3-a40a-510ef06156e2.mp4

Trac ticket: https://core.trac.wordpress.org/ticket/54680

cc/ @hellofromtonya @noisysocks @youknowriad -- I think this should go into 5.9 :)

Thanks for the PR! This looks good to me. It would also be great to include a unit test for this, some other tests in the phpunit/tests/rest-api/wpRestTemplatesController.php file could be used as a reference.

Thanks for the PR! This looks good to me. It would also be great to include a unit test for this, some other tests in the phpunit/tests/rest-api/wpRestTemplatesController.php file could be used as a reference.

Sure, happy to add a test!

[hellofromTonya]

Ready for commit.

Thanks a lot for reviewing @SergeyBiryukov @rachelbaker @hellofromtonya!

Since I don't have Core commit privileges myself, can I ask one of you kind souls to commit this? 😄

Thanks a lot for reviewing @SergeyBiryukov @rachelbaker @hellofromtonya!

Since I don't have Core commit privileges myself, can I ask one of you kind souls to commit this? 😄

[audrasjb]

Self assigning for commit.

[audrasjb]

Worth noting this was already fixed in this commit: ​https://github.com/WordPress/wordpress-develop/commit/bd08b221273b8b367a18fef8c9efb873819ac89d#diff-d52bf95054b516a19c2a332fd0c85bdbab2cb8e5a25756a12b99128744262144

I'll only commit the unit tests :)

[audrasjb]

In 52436:

REST API: Add unit tests for the 404 template slug handler.

Props ockham, SergeyBiryukov, hellofromTonya, rachelbaker.
Fixes #54680.

Committed in https://core.trac.wordpress.org/changeset/52436