RUBY-2295 include collation option in count_documents (#1984)

* RUBY-2295 include collation option in count_documents

* RUBY-2295 clean up some code

Author: neilshweky

lib/mongo/collection/view/readable.rb

@@ -185,7 +185,9 @@ def count_documents(opts = {})
           pipeline << { :'$limit' => opts[:limit] } if opts[:limit]
           pipeline << { :'$group' => { _id: 1, n: { :'$sum' => 1 } } }
 
-          opts.select! { |k, _| [:hint, :max_time_ms, :read, :collation, :session].include?(k) }
+          opts = opts.select { |k, _| [:hint, :max_time_ms, :read, :collation, :session].include?(k) }
+          opts[:collation] ||= collation
+
           first = aggregate(pipeline, opts).first
           return 0 unless first
           first['n'].to_i

spec/mongo/collection_spec.rb

@@ -945,6 +945,28 @@
         it_behaves_like 'a failed operation using a session'
       end
     end
+
+    context 'when collation has a strength' do 
+      let(:band_collection) do 
+        described_class.new(database, :bands)
+      end
+
+      before do
+        band_collection.delete_many
+        band_collection.insert_many([{ name: "Depeche Mode" }, { name: "New Order" }])
+      end
+
+      let(:options) do 
+        { collation: { locale: 'en_US', strength: 2 } }
+      end
+      let(:band_result) do 
+        band_collection.find({ name: 'DEPECHE MODE' }, options)
+      end
+
+      it 'finds Capitalize from UPPER CASE' do 
+        expect(band_result.count_documents).to eq(1)
+      end
+    end
   end
 
   describe '#drop' do