fix: apply price post-filtering before counting and pagination

[florianthomi]

The price post-filter recomputes each product's real price for the current customer group and drops the ones outside the requested range. It ran after array_slice(), so the total and page count kept their pre-filter values and a whole page could end up empty while the listing announced dozens of results.

Applying it to the full result list keeps the count, the pagination and the rendered products consistent.

Questions	Answers
Description?	The price post-filter runs after pagination, so the announced total and page count don't match the products actually rendered : a filtered page can come back empty. Moving it before the count fixes both. Reproduced on PrestaShop 8.2.7 with ps_facetedsearch dev.
Type?	bug fix
BC breaks?	no
Deprecations?	no
Fixed ticket?	#1280
How to test?	See below.
Sponsor company	iomedia

Problem

Products::getProductByFilters() builds the result list in this order:

1. SQL query against ps_layered_price_index, which stores, per product, the envelope of prices across all customer groups and specific prices;
2. count() : the total shown to the customer;
3. array_slice() : the current page;
4. pricePostFiltering() : recomputes each product's real price for the current customer group via Product::getPriceStatic() and drops the ones outside the requested range.

Step 4 only ever sees the current page, and it runs after the count. So the total and the page count keep their pre-filter values while the grid is silently shortened. On a shop where several groups have a discount, the indexed envelope is much wider than any single visitor's real price, and a whole page can be emptied: the listing announces "62 results / 6 pages" and renders nothing.

The same slice is also used to decide what page 2 contains, so products dropped on page 1 are never shown at all, they are not pushed to the next page.

Fix

Apply the post-filter to the full result list, before counting and slicing.

How to test

1. PrestaShop 8.x with demo data, ps_facetedsearch enabled with a price filter on a category.
2. Customers > Groups > Customer — set a 25% discount. This widens every product's indexed price range.
3. Module configuration > rebuild the price index (or run ps_facetedsearch-price-indexer.php).
4. As a guest, open the category and pick a price range that sits below most products' public prices, e.g. the lower half of the slider.

Before: the header announces a large number of results across several pages, while the grid shows few or no products; summing the products across all pages never reaches the announced total.

After: the announced total equals the number of products actually reachable across the pages, every page is full except the last, and no product appears twice or goes missing.

Trade-off

Product::getPriceStatic() now runs for every product whose indexed range straddles a filter bound, instead of only those on the current page. It is only reached when a price filter is active, only for straddling products, and getPriceStatic() has a static cache, but on a large catalogue with wide group discounts this is more work per request than before. It seemed preferable to a listing that reports numbers it cannot deliver.

[ps-jarvis]

Hello @florianthomi!

This is your first pull request on ps_facetedsearch repository of the PrestaShop project.

Thank you, and welcome to this Open Source community!