add to_query! for stricter validations

README.md

@@ -67,6 +67,16 @@ query.to_query(params[:q])
 # => { name: 'Pablo', '$or' => { middle_name: /Cantero/i, last_name: /Cantero/i } }
 ```
 
+### to_query!
+
+You can use to_query! for stricter validations. This method will raise an exception if a query cannot be produced.
+```ruby
+query.to_query({ name: 'Pablo' })
+# => {}
+query.to_query!({ name: 'Pablo' })
+# => RansackMongo::MatcherNotFound: No matchers found. To allow empty queries use .to_query instead
+```
+
 ## Contributing
 
 1. Fork it ( https://github.com/phstc/ransack_mongo/fork )

lib/ransack_mongo/query.rb

@@ -34,6 +34,16 @@ module RansackMongo
       db_adapter.to_query
     end
 
+    def to_query!(params)
+      selector = to_query params
+
+      if selector.empty?
+        raise MatcherNotFound,  "No matchers found. To allow empty queries use .to_query instead"
+      end
+
+      selector
+    end
+
     def or_query(db_adapter, attr, value, p)
       db_adapter.or_op do
         attr.split('_or_').each do |or_attr|

spec/ransack_mongo/query_spec.rb

@@ -32,6 +32,19 @@ module RansackMongo
     end
 
     context 'when MongoAdapter' do
+      describe '#to_query!' do
+        it 'raises exception when query evaluates to an empty hash' do
+          params = { 'name' => 'Pablo' }
+          expect { described_class.new.to_query!(params) }.to raise_error(MatcherNotFound)
+        end
+
+        it 'returns the query' do
+          params = { 'name_eq' => 'Pablo', 'fullname_cont' => 'Cantero' }
+
+          expect(described_class.new.to_query!(params)).to eq('name' => 'Pablo', 'fullname' => /Cantero/i)
+        end
+      end
+
       describe '#to_query' do
         it 'returns the query' do
           params = { 'name_eq' => 'Pablo', 'fullname_cont' => 'Cantero' }