Now serializing empty lists for the query protocol.

Fixes #49

Author: trevorrowe

lib/aws/query/builder.rb

@@ -38,6 +38,10 @@ def structure(param_list, shape, prefix, values)
       end
 
       def list(param_list, shape, prefix, values)
+        if values.empty?
+          param_list.set(prefix, '')
+          return
+        end
         member_shape = shape.members
         if flat?(shape)
           if member_shape.serialized_name

spec/aws/query/builder_spec.rb

@@ -132,6 +132,26 @@ def query_params(params = {})
             ])
           end
 
+          it 'serializes empty lists' do
+            rules['members'] = {
+              'config' => {
+                'type' => 'structure',
+                'members' => {
+                  'items' => {
+                    'type' => 'flat_list',
+                    'members' => {
+                      'type' => 'string'
+                    }
+                  }
+                }
+              }
+            }
+            params = { config: { items: [] }}
+            expect(query_params(params)).to eq([
+              ['config.items', ''],
+            ])
+          end
+
         end
 
         describe 'non-flattened lists' do
@@ -192,6 +212,26 @@ def query_params(params = {})
             ])
           end
 
+          it 'serializes empty lists' do
+            rules['members'] = {
+              'config' => {
+                'type' => 'structure',
+                'members' => {
+                  'items' => {
+                    'type' => 'list',
+                    'members' => {
+                      'type' => 'string'
+                    }
+                  }
+                }
+              }
+            }
+            params = { config: { items: [] }}
+            expect(query_params(params)).to eq([
+              ['config.items', ''],
+            ])
+          end
+
         end
 
         describe 'flattened maps' do