Block Hooks API: Add Templates Controller filter to avoid triggering wp_update_post

[tjcafferkey]

This change is inspired by this PR WordPress/gutenberg#59561 since they are suffering from the same problem.

By creating a rest_pre_insert_{$this->post_type} filter in theWP_REST_Templates_Controller rather than using the rest_insert_{$this->post_type} action. This avoids calling wp_update_post twice, which was the original reason for the issue, as it removed the backslash from the already-encoded entity. I suspect wp_update_post was also creating additional revisions which was mentioned in the linked Trac ticket.

By creating this filter it also creates consistency with the WP_REST_Posts_Controller which has the same filter.

Trac ticket: https://core.trac.wordpress.org/ticket/60671

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The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

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Props tomjcafferkey, bernhard-reiter, gziolo, swissspidy, karolmanijak.

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[ockham]

This should be ready for review 😊

[gziolo]

By creating this filter it also creates consistency with the WP_REST_Posts_Controller which has the same filter.

That makes sense to me. Avoiding two database operations should be one of the goals of this fix. See my #6225 (comment), where I'm unsure if it will work as intended for the logic that injects blocks.

[swissspidy]

Is there test coverage? Can we add tests.

[kmanijak]

I tested the PR against the original issue and it works just fine! Thanks @tjcafferkey for picking it up 🚀

[ockham]

Is there test coverage? Can we add tests.

I'll add some 👍

[ockham]

@swissspidy I've added some tests, both for the filter in isolation, and when used inside the controller. LMK if this looks good to you, or if you'd like anything else covered 🙂

[gziolo]

Looks good to me 👍🏻

[ockham]

Committed to Core in https://core.trac.wordpress.org/changeset/57790.

[ockham]

Backported to the 6.5 branch in https://core.trac.wordpress.org/changeset/57802.