Coerce_with nil value but not the missing fields

Author: Braktar

lib/grape/validations/types/custom_type_coercer.rb

@@ -52,8 +52,6 @@ def initialize(type, method = nil)
         #   this should always be a string.
         # @return [Object] the coerced result
         def call(val)
-          return if val.nil?
-
           coerced_val = @method.call(val)
 
           return coerced_val if coerced_val.is_a?(InvalidValue)

spec/grape/validations/validators/coerce_spec.rb

@@ -754,6 +754,44 @@ def self.parse(_val)
         expect(last_response.body).to eq('3')
       end
 
+      context 'Integer type and coerce_with should' do
+        before do
+          subject.params do
+            optional :int, type: Integer, coerce_with: (lambda do |val|
+              if val.nil?
+                0
+              else
+                val.to_i
+              end
+            end)
+          end
+          subject.get '/' do
+            params[:int].class.to_s
+          end
+        end
+
+        it 'coerce nil value to integer' do
+          get '/', int: nil
+
+          expect(last_response.status).to eq(200)
+          expect(last_response.body).to eq('Integer')
+        end
+
+        it 'not coerce missing field' do
+          get '/'
+
+          expect(last_response.status).to eq(200)
+          expect(last_response.body).to eq('NilClass')
+        end
+
+        it 'coerce integer as integer' do
+          get '/', int: 1
+
+          expect(last_response.status).to eq(200)
+          expect(last_response.body).to eq('Integer')
+        end
+      end
+
       context 'Integer type and coerce_with potentially returning nil' do
         before do
           subject.params do