[Backport 8.x] Backport #3495: Ensure that facet suggestions are rele…

…vant to the user's query (#3501)

* Ensure that facet suggestions are relevant to the user's query

Before this commit, the facet suggest javascript sent HTTP
requests that included only the name of the facet and the
fragment that the user entered to filter down the facets.

This commit also sends any URL params that were in the user's
original search, so that the facet suggestions are relevant
to the search, rather than being just the most popular facet
values from the entire corpus.

Closes #3494

* Put test into configured context

---------

Co-authored-by: Max Kadel <mkadel@princeton.edu>

app/javascript/blacklight/facet_suggest.js

@@ -6,7 +6,7 @@ const FacetSuggest = async (e) => {
     const facetField = e.target.dataset.facetField;
     if (!facetField) { return; }
 
-    const urlToFetch = `/catalog/facet_suggest/${facetField}/${queryFragment}`
+    const urlToFetch = `/catalog/facet_suggest/${facetField}/${queryFragment}${window.location.search}`
     const response = await fetch(urlToFetch);
     if (response.ok) {
         const blob = await response.blob()

spec/features/facets_spec.rb

@@ -117,6 +117,14 @@
         expect(page).to have_link 'Old age'
         expect(page).to have_css 'a.facet-select', count: 2
       end
+
+      it 'shows the user facet suggestions that are relevant to their q param', :js do
+        visit '/catalog/facet/subject_ssim?q=tibet&search_field=all_fields'
+        fill_in 'facet_suggest_subject_ssim', with: 'la'
+
+        expect(page).to have_link 'Tibetan language'
+        expect(page).to have_css 'a.facet-select', count: 1
+      end
     end
   end
 end