Only ensure session on single product pages

[claudiulodro]

Issue: #777

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Description

This PR improves the session handling to prevent caching issues. It does this by only initializing the session (if needed) on single product pages. Since a session without adding anything to the cart is only required when checking out from single product pages, this should dramatically reduce the number of sessions that are created.

Steps to test:

0. Set up this gateway with the "Check out on single product" setting enabled.
1. Before applying this patch, in a new incognito window visit the site with the network inspector open. Observe a session starts on the first page load on the homepage:

2. Apply this patch. Start a fresh incognito window. Visit the site with the network inspector open. Observe no session is created on the homepage:

3. Visit a single product page, observe the session is created:

Documentation

• [ ] This PR needs documentation (has the "Documentation" label).

Closes #777 .

[achyuthajoy]

Nice one @claudiulodro. I was working on something similar a few weeks back but never got the chance to submit.

$frontend = (
    ( ! is_admin() || defined( 'DOING_AJAX' ) ) &&
    ( is_product() || is_checkout() || ( is_cart() && ! WC()->cart->is_empty() ) ) &&
    ! ( defined( 'DOING_CRON' ) && defined( 'REST_REQUEST' ) )
);

Create WC Session Cookie if:

• Not Admin Page or AJAX and
• Not CRON or REST and
• Is Product or Checkout or is Cart & Cart not empty

It seems your solution is a lot cleaner 👍

[claudiulodro]

Thanks!

I think the Cart/Checkout checks aren't necessary:

• If it's a Cart or Checkout page and a product is in the cart, there will always already be a session cookie (for keeping track of the products in the cart)
• If it's a Cart or Checkout page and no product is in the cart, the user is not going to be able to checkout (what would they be purchasing?? 😄 )

So the only situation this needs to handle is single product pages.

[jorgeatorres]

Hi @claudiulodro!

This looks good. I've rebased the changes on the latest trunk and also pushed a commit to account for #845, which was something we added after you submitted this PR. Once Travis gives me the green light, I'll merge the PR.

[jorgeatorres]

Tests I ran on this branch:

• [x] With PayPal disabled on single page:
  • [x] Pay with PayPal from Cart page.
  • [x] Pay with PayPal from Checkout page.
  • [x] Pay with PayPal on the 'order-pay' endpoint.
• [x] With PayPal enabled on single page:
  • [x] Pay with PayPal from Cart page.
  • [x] Pay with PayPal from Checkout page.
  • [x] Pay with PayPal on the 'order-pay' endpoint.
  • [x] Pay with PayPal on the single product page.