Sharing Block: refactor block markup output

[jeherve]

Follow-up to #35354

Proposed changes:

Add extra fallback values, reorganize, and do not rely on global

• We really only need the post ID, not the full $post object, so we can update the 2 functions to use only the post ID that is pulled from the block context.
• Let's add some extra fallback values when some values are not provided by the block context.
• Let's only add the SVG if it is needed in the markup. When folks are using the text-only style, we do not need to output the SVG in the markup.
• Let's reorganize the markup output to escape as late as possible, and clearly indicate what is escaped and how. It should make it more readable and easier to understand to new contributors.
• Update docblock to avoid notices in editor

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

• N/A

Does this pull request change what data or activity we track or use?

• No

Testing instructions:

• Enable Beta blocks on your site:

add_filter( 'jetpack_blocks_variation', function () {
	return 'beta';
} );

• Switch to a block-based theme like Twenty Twenty Four
• Go to Appearance > Site Editor > Templates > Single Posts
• Add a Sharing block to your template
• Add different buttons
• Play with the different settings:
  • Button style
  • Button size
  • Button color (foreground and background)
• Ensure that your changes are properly displayed on the frontend.
• Ensure that clicking on the buttons works.
• Ensure that when reloading the editor screen, no error shows.

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WordPress.com Simple site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin, and enable the update/sharing-block-markup branch.

• To test on Simple, run the following command on your sandbox:

  bin/jetpack-downloader test jetpack update/sharing-block-markup
  

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

Thank you for your PR!

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[andrii-lysenko]

Thanks for working on this. It looks great and tests well.

One nitpick, in class-sharing-source-block we have over overriden function get_link in Share_Email_Block which we probably need to update to use $post_id. For some reason it still works even now, but probably better to update.

[jeherve]

Good call! Done in 5009edc

[andrii-lysenko]

Looks great! Thanks!