Add MailChimp Widget

[stoyan0v]

Fixes #5942

Adds the MailChimp Subscribe Popup widget. It basically uses the mailchimp_subscriber_popup shortcode to add the script and I've tried to match the WordPress.com widget as much as possible.

Testing instructions:

• Go to Widgets
• Find "MailChimp Subscriber Popup" and add the widget to any sidebar
• Add the following embedcode in "Code" field:

<script type="text/javascript" src="//s3.amazonaws.com/downloads.mailchimp.com/js/signup-forms/popup/embed.js" data-dojo-config="usePlainJson: true, isDebug: false"></script><script type="text/javascript">require(["mojo/signup-forms/Loader"], function(L) { L.start({"baseUrl":"mc.us11.list-manage.com","uuid":"1ca7856462585a934b8674c71","lid":"2d24f1898b"}) })</script>

• Open the front-end and you should see the popup
• If the popup doesn't appear for some reason, check if the code exists in the sidebar. It's easier if you add the widget between two others that have some content/html.

cc @jeherve, @eliorivero

[jeherve]

Since you rely on the shortcode here, you'll need to make sure the shortcode is declared before to register this widget, otherwise this will fail as soon as someone disables the Shortcode Embeds module, or unregisters the shortcode.

Maybe you could check if the MailChimp_Subscriber_Popup class exists in the jetpack_mailchimp_subscriber_popup_widget_init function, before to register the widget?

[stoyan0v]

Good catch. The check has been added, so the widget will not be registered when shortcode is missing for some reason.

[jeherve]

Maybe you could add a title to this widget?

[stoyan0v]

I don't think so. The widget displays a script tag only, so the title here is useless, since it will not be displayed.

[rcoll]

This doesn't display a widget in the traditional manner, so I would say no title is necessary.

[jeherve]

It might be worth being more specific here: Code does not explain what code the user has to enter here.

[stoyan0v]

Make sense. I've added a link to this page, similar to wordpress.com

[rcoll]

This works well and code looks fine to me. I do recommend a trim() in the update method to remove leading and trailing whitespace, but that's purely cosmetic. Thanks!

[rcoll]

One other note - I'm not in love with the execution on this (using a widget to display a script tag with no widget content), but I don't really know of a better/quicker way. This does work fine and shouldn't break anything, but maybe we need a better strategy for these types of things.