Standalone Block Registration/Block Dependencies

[jeffersonrabb]

This adds a few pieces needed for the Map block (and similar future ones) to work following recent changes to block building and view script loading in #10405 and Automattic/wp-calypso#28066.

Fixes

1. The Map block doesn't correspond to a pre-Gutenberg Jetpack module, so it needs a new structure for PHP registration. For normal modules this is done in their dedicated directory in modules/. Here, this is done in modules/blocks.php.
2. The Map block has a few view-side dependencies, and this PR creates a way to declare these.

Testing instructions:

To test the Map block, it will need to be built from the https://github.com/Automattic/wp-calypso/tree/try/map-key branch. The Calypso branch resolves a naming consistency problem (map vs. maps-block) and temporarily adds a hardcoded Google Maps API key so it can be used without the changes in https://github.com/Automattic/wp-calypso/tree/try/map-key. This Calypso branch is meant only for testing with this PR, and will be deleted after this PR merges.

To test with Jetpack docker:

1. Checkout wp-calypso branch try/map-key.
2. Checkout jetpack branch try/block-dependencies.
3. Build Map block by running this SDK command from the root of wp-calypso repo: npm run sdk gutenberg client/gutenberg/extensions/presets/jetpack -- --output-dir=PATH_TO_JETPACK_REPO/_inc/blocks. (Replace PATH_TO_JETPACK_REPO with relevant path).
4. In Jetpack repo, verify that _inc/blocks/map/ exists and contains view.css|view.js|view.rtl.css.
5. Create a post, add Map block, publish.

To test with Jurassic Ninja use this link:

https://jurassic.ninja/create/?gutenberg&gutenpack&shortlived&jetpack-beta&calypsobranch=try/map-key&branch=try/block-dependencies

Flows to verify

1: Verify that Map block loads and renders in editor and view. If the view.js or any of the dependencies are missing the block will be completely blank.

2: In view, watch Network tab to verify that all dependent Javascript files are loading. Among others you should see:

• /wp-content/plugins/jetpack/_inc/blocks/map/view.js
• /wp-content/plugins/gutenberg/vendor/react-dom.min
• /wp-content/plugins/gutenberg/vendor/react.min.ab6b06d4.js (or similar)
• /wp-content/plugins/gutenberg/build/element/index.js
• /wp-content/plugins/gutenberg/build/i18n/index.js
• /wp-content/plugins/gutenberg/build/api-fetch/index.js

3: Remove the map block (or create a second post without it), publish and view. In the Network tab none of the above files should be loading.

Proposed changelog entry for your changes:

• Add module/blocks.php file for registration of blocks without corresponding modules.
• Allow individual blocks to declare their view dependencies.

[jetpackbot]

Thank you for the great PR description!

When this PR is ready for review, please apply the [Status] Needs Review label. If you are an a11n, please have someone from your team review the code if possible. The Jetpack team will also review this PR and merge it to be included in the next Jetpack release.

Scheduled Jetpack release: December 4, 2018.
Scheduled code freeze: November 27, 2018

Generated by 🚫 dangerJS

[enejb]

Beside the minor renaming of things I think this works as expected. I tested this with the JN link above and it worked as expected.

[jeherve]

A few minor improvements that I think we could make.

[jeherve]

It works well on my end. 👍

[kraftbj]

Good for me too. @jeffersonrabb feel free to merge if you're ready to have it land.