Fix URL generation when explicitly passing params to link helpers

kaminari-core/lib/kaminari/helpers/tags.rb

@@ -24,7 +24,14 @@ def initialize(template, params: {}, param_name: nil, theme: nil, views_prefix:
         @params = @params.to_unsafe_h if @params.respond_to?(:to_unsafe_h)
         @params = @params.with_indifferent_access
         @params.except!(*PARAM_KEY_BLACKLIST)
-        @params.merge! params
+        # params in Rails 5 may not be a Hash either,
+        # so it must be converted to a Hash to be merged into @params
+        unless params.empty?
+          ActiveSupport::Deprecation.warn 'Explicitly passing params to helpers could be removed in the future.'
+          params = params.to_unsafe_h if params.respond_to?(:to_unsafe_h)
+          params = params.with_indifferent_access
+          @params.merge! params
+        end
       end
 
       def to_s(locals = {}) #:nodoc:

kaminari-core/test/helpers/tags_test.rb

@@ -67,6 +67,20 @@ class TagTest < ActionView::TestCase
         end
       end
 
+      sub_test_case "when passing nested params" do
+        setup do
+          self.params[:filter] = ActionController::Parameters.new({status: 'active'})
+        end
+
+        test 'for first page' do
+          assert_match(/users\?filter%5Bstatus%5D=active/, Kaminari::Helpers::Tag.new(self, params: self.params).page_url_for(1))
+        end
+
+        test 'for other page' do
+          assert_match(/users\?filter%5Bstatus%5D=active&page=2/, Kaminari::Helpers::Tag.new(self, params: self.params).page_url_for(2))
+        end
+      end
+
       sub_test_case "with param_name = 'foo.page' option" do
         setup do
           self.params['foo.page'] = 2