Fixed subscribe block redirect issue on non-post pages

[TimBroddin]

Proposed changes:

The subscribe block was incorrectly redirecting to the post from get_the_ID() when used on the homepage and archive pages.

This PR also contains a small fix to bind the showing of the subscribe modal to all subscribe forms on the page.

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

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

No

Testing instructions:

• Apply this PR
• Change the design of your blog:
  • Add a subscribe block to the footer
  • Show post content inside the post loop for the homepage
• Create a post with a subscribe block
• Inspect the subscribe blocks using developer tools:
  • When on the home page the footer subscribe block shouldn't contain a hidden post_id field
  • The subscribe block inside the post loop should contain a hidden post_id field containing the post_id of the post being shown
  • Both subscribe blocks on the post detail (single) page should contain a hidden post_id field containing the post_id of the post being shown

You can also try subscribing using the different blocks, the one in the footer on the home page should redirect to Reader > Manage Subscriptions while the other ones should redirect to the post.

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

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[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 fix/subscribe-form-redirect-to-post-bug branch.

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

  bin/jetpack-downloader test jetpack fix/subscribe-form-redirect-to-post-bug
  

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.
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• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[TimBroddin]

Rebasing this later today.

[simison]

Rebased since I'm testing anyway. :-)

[simison]

Something like this would also catch pages, and always have a fallback for the homepage? I'd like to avoid sending to subscription management in any situation.

if ( in_the_loop() ) {
	$post_id = get_the_ID();
} elseif ( is_singular( 'post' ) || is_page() ) {
	$post_id = get_queried_object_id();
} else {
	$post_id = get_option( 'page_on_front' );
}

[simison]

#34086

[simison]

Let's get this in and iterate.