Inject "Add New Theme" button on Theme screen for simple sites

[ryelle]

This PR adds the same "Add New Theme" button that appears on core WordPress sites to simple wpcom sites. Currently, I have it directing to the Calypso Theme Showcase, as https://yoursite.wordpress.com/wp-admin/theme-install.php does not work for simple sites. If/when the theme showcase is moved to a wp-admin page, this can be replaced with the core URL.

Fixes Automattic/wp-calypso#96393

Screenshots

Note that when a site has the "classic" dashboard mode selected, this banner appears on the theme screen with the "Explore" button, which also leads to the Theme Showcase.

Before	After

On simple sites the calypso dashboard mode, if you go directly to the wp-admin/themes.php page, you don't get the banner. But this still adds the button.

Before	After

Atomic sites already have the button, no change needed here.

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)?

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

I don't think this applies, but I did tweak the URL target for the button, to https://wordpress.com/themes/$site_slug?ref=wpcom-themes-add — same format as the banner, but a new ref. I'm not familiar with whatever we use to track now to know if that needs to be set up somewhere else.

Testing instructions:

1. Use a simple site with the "Classic" dashboard mode; or go directly to site.wordpress.com/wp-admin/themes.php
2. Go to Appearance > Themes
3. You should see the page title Themes, and next to that is the "Add New Theme" button
4. Clicking that will take you to the theme showcase, allowing you to select a new theme

[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 add/themes-add-new-button branch.

  • For jetpack-mu-wpcom changes, also add define( 'JETPACK_MU_WPCOM_LOAD_VIA_BETA_PLUGIN', true ); to your wp-config.php file.

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

  bin/jetpack-downloader test jetpack-mu-wpcom-plugin add/themes-add-new-button
  

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]

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[ryelle]

This seemed like the easiest place to add this, but perhaps the containing function name should be changed? (from wpcom_themes_remove_wpcom_actions)

[scruffian]

Thanks for this. I have two questions:

1. Why you do this in Jetpack rather than on wpcom?
2. Why use a JS solution rather than modifying themes.php directly?

[ryelle]

Why you do this in Jetpack rather than on wpcom?

This is in the mu-plugin that jetpack builds into wpcom. There was already other theme-related code here. If there's a better place for it I'm happy to move it.

Why use a JS solution

I didn't use a PHP solution because there are no hooks into the page title area. The JS solution gets the button right where it needs to go.

rather than modifying themes.php directly?

Is there a process for modifying core files on wpcom?