Pass rel_opts when filtering records for record count

Naturally I uncovered this because it caused a more complex bug in my app.
The problem here is that if you have a filter which depends on something
that is set in, for example, the context, you will not have that context
when the filter is re-invoked for record count, which happens when the
record count configuration is active. This only happens when fetching
related resources.

In this case I add a test where we try to fetch an author's banned books,
of which there should be only one. However, because the prior code
discards the rel_opts and instead provides an empty hash (!) the filter
does not execute because it will only operate when an admin user is in
the context.

Closes gh-1234

Author: hatch-carl

lib/jsonapi/processor.rb

@@ -197,7 +197,7 @@ def show_related_resources
           (paginator && paginator.class.requires_record_count) ||
           (JSONAPI.configuration.top_level_meta_include_page_count))
         related_resource_records = source_resource.public_send("records_for_" + relationship_type)
-        records = resource_klass.filter_records(verified_filters, {},
+        records = resource_klass.filter_records(verified_filters, rel_opts,
                                                 related_resource_records)
 
         record_count = resource_klass.count_records(records)

test/controllers/controller_test.rb

@@ -2754,6 +2754,45 @@ def test_get_related_resources_with_filters
   end
 end
 
+class Api::V2::BooksControllerTest < ActionController::TestCase
+  def test_get_related_resources_with_filters
+    $test_user = Person.find(5)
+    original_config = JSONAPI.configuration.dup
+    JSONAPI.configuration.top_level_meta_include_record_count = true
+    JSONAPI.configuration.json_key_format = :dasherized_key
+    assert_cacheable_get :get_related_resources,
+                         params: {
+                           author_id: '1',
+                           relationship: 'books',
+                           source: 'api/v2/authors',
+                           filter: { fiction: 'true' }
+                         }
+    assert_response :success
+    assert_equal 1, json_response['meta']['record-count']
+  ensure
+    JSONAPI.configuration = original_config
+  end
+
+  def test_get_related_resources_with_filters_2
+    # Admin user can find an author's banned books
+    $test_user = Person.find(5)
+    original_config = JSONAPI.configuration.dup
+    JSONAPI.configuration.top_level_meta_include_record_count = true
+    JSONAPI.configuration.json_key_format = :dasherized_key
+    assert_cacheable_get :get_related_resources,
+                         params: {
+                           author_id: '1',
+                           relationship: 'books',
+                           source: 'api/v2/authors',
+                           filter: { banned: 'true' }
+                         }
+    assert_response :success
+    assert_equal 1, json_response['meta']['record-count']
+  ensure
+    JSONAPI.configuration = original_config
+  end
+end
+
 class BreedsControllerTest < ActionController::TestCase
   # Note: Breed names go through the TitleValueFormatter
 

test/fixtures/active_record.rb

@@ -1552,6 +1552,8 @@ def apply_filter_banned(records, value, options)
           # Only book admins might filter for banned books
           if current_user && current_user.book_admin
             records.where('books.banned = ?', value[0] == 'true')
+          else
+            records
           end
         end