Search results don't boost recommended addons when searching without a query string

[AlexandraMoga]

[Recommended add-ons]
Follow up for #6525

STR:

1. Open AMO -dev
2. Try to search for add-on without providing a query string- i.e. https://addons-dev.allizom.org/en-US/firefox/search/ or https://addons-dev.allizom.org/en-US/firefox/search/?type=extension
3. Observe the results

Actual result:
As per @eviljeff 's comment in #6525, when no search string is provided , the API defaults to weekly downloads. On -dev, at least, this means that recommended add-ons are not boosted in search results

Expected result:
Since we plan to boost recommended extensions in search results, I would expect to see the add-ons from the curated list on the first pages of results when no search string was provided.

Notes:

• the PRD doesn't mention an approach for this specific scenario

[eviljeff]

@jvillalobos / @atsay what you think? For the specific case of searching with no search string?

(And in general, about non-relevance sorting - e.g. weekly downloads, users, etc.)

[eviljeff]

I've an idea: we default to random sort if ?recommended and no query string.

[jvillalobos]

The PRD mentions "If this flag is selected and there’s no search query, the default sort should be ADI."

[eviljeff]

What about when the flag isn't selected like in the urls @AlexandraMoga posted above (sorry for muddying the waters by mentioning the case when ?recommended is present).

[jvillalobos]

Users should be the default sort whenever a search doesn't have a query string and doesn't have a sort. The only exception is when searching specifically for search engines (/search/?type=search), which should be sorted by rating (see #13034).

[jvillalobos]

Just discussed this with @atsay and she had a good point about showing Recommended on top in these cases. So, amending my previous comment:

Default: Recommended first, sorted by users, followed by the rest, sorted by users.
Search engines: Sorted by ratings (we don't plan to recommend those).

Does that make sense, @eviljeff?