Add support for Comet Cache Pro logged-in user caching

[raamdev]

s2Member currently supports ZenCache logged-in user caching, however now that ZenCache has been renamed to Comet Cache we need to update the s2Member codebase to work properly with the new plugin.

Forked from wpsharks/comet-cache#676.

[jaswrks]

Next Release Changelog:

• (s2Member/s2Member Pro) Comet Cache Compat.: This release improves compatibility with Comet Cache (formerly ZenCache), whenever you have it configured to cache logged-in users. See also: this GitHub issue. Props @KTS915 for reporting!

[KTS915]

Wow! That was quick!

[raamdev]

@jaswsinc In wpsharks/comet-cache#676 (comment) you write...

We have some additional code in the s2Member plugin itself that accomplishes full compatibility between the two.

Can you elaborate on what "full compatibility" means? I was just testing the v160225-RC that includes your work to improve compatibility with Comet Cache, however it's clear to me that some pages are not going to be cached by Comet Cache due to the fact that the page contains a Pro-Form or other dynamic s2Member content.

The article on the s2Member site that @KTS915 linked to in the other GitHub issue doesn't seem to be very clear on what compatibility means either:

it works in complete and total harmony with all s2Member features—without any additional configuration needed whatsoever.

Tip: Comet Cache has a unique ability to cache logged-in users too, which is highly effective whenever it runs alongside the s2Member Pro application; keeping WordPress fast even when a user is logged in as a member. Very impressive!

https://s2member.com/kb-article/is-s2member-compatible-with-caching-plugins/

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Would you mind clarifying what we can expect from from s2Member's compatibility with Comet Cache? The fact that this isn't clear to me is making testing this fix in the RC rather difficult (I'm not entirely sure what should and what should not be working).

[jaswrks]

s2Member will prevent caching on user-specific and/or dynamic content (e.g., Posts/Pages that contain an s2Member shortcode or conditional tag, the MOP and LWP, etc) whenever a user is logged in. This is an additional precaution on the part of s2Member to ensure that dynamic content it generates is never cached for any specific user and then displayed to another from the cache.

However, whenever Comet Cache (and ZenCache in the past) are running with user-specific caching enabled, s2Member can allow this to occur, because our plugins do in fact allow for user-specific content to be cached in an intelligent way. For this reason, there must be conditionals in s2Member that will look for the presence of these user-cache-compatible plugins like Comet Cache and ZenCache. If they are running and configured to allow for a user-specific cache, we allow those pages to be cached as one would expect them to be.

[raamdev]

For this reason, there must be conditionals in s2Member that will look for the presence of these user-cache-compatible plugins like Comet Cache and ZenCache. If they are running and configured to allow for a user-specific cache, we allow those pages to be cached as one would expect them to be.

So the s2Member Login Welcome Page should get cached by Comet Cache when Logged-In User caching is enabled? If so, that does not appear to be happening with Comet Cache Pro v160223.1 + s2Member Pro v160225-RC:

<!-- Comet Cache is NOT caching this page, because the s2Member plugin set the PHP constant `COMET_CACHE_ALLOWED` to a boolean-ish `FALSE` value at runtime. The s2Member plugin is serving content that must remain dynamic on this particular page, and therefore this page was intentionally not cached for a very good reason. -->

[jaswrks]

@raamdev I was unable to reproduce this. Did you have the [s2Member-Profile /] shortcode on the page or any other shortcode perhaps?

[jaswrks]

I see. I was able to reproduce this when there are shortcodes present. I need to have another look at why we chose to do that even when logged-in caching is enabled.