Reset previous sorting rules before adding an attribute sort rule

[taskula]

Our catalog widget in Magento 2.3.2 is sorting by created_at by default as seen:
"ORDER BY e.created_at desc, cat_index.position ASC LIMIT 10"

This PR resets previous sort rules and makes created_at sorting secondary.

[rianorie]

@taskula Looks good! I'm curious though, why the load() call? That will negate the lazy loading..

[niclashoyer]

I just had the same issue and it really did not work when not using load(). Without the load() call the resulting SELECT query just did not have the ORDER BY clause.

[niclashoyer]

One other problem I noticed is that the collection is loaded correctly, sorted correctly, running the SQL query manually shows the correct order, but in the frontend the widget still shows another order 😞

[niclashoyer]

After some more digging I actually found the error on why it is not possible to sort by position:

When the product collection is created, Magento uses the default root category, because the widget can be embedded anywhere. Afterwars it is possible to add rules to filter for category id, but as the collection was created using the root category, the query uses the positions from the root category instead of the category that is filtered.

I worked around this by replacing the product collection with a new collection alltogether.