[go-server] Set default values in object properties

When a default value is set for an object property, ensure it is set
into the struct before decoding the JSON body.

Fix OpenAPITools#4579

modules/openapi-generator/src/main/resources/go-server/controller-api.mustache

@@ -591,7 +591,12 @@ func (c *{{classname}}Controller) {{nickname}}(w http.ResponseWriter, r *http.Re
 	{{paramName}}Param := r.Header.Get("{{baseName}}")
 	{{/isHeaderParam}}
 	{{#isBodyParam}}
+	{{#isArray}}
 	{{paramName}}Param := {{dataType}}{}
+	{{/isArray}}
+	{{^isArray}}
+	{{paramName}}Param := New{{dataType}}WithDefaults()
+	{{/isArray}}
 	d := json.NewDecoder(r.Body)
 	{{^isAdditionalPropertiesTrue}}
 	d.DisallowUnknownFields()

modules/openapi-generator/src/main/resources/go-server/model.mustache

@@ -74,7 +74,34 @@ type {{classname}} struct {
 	{{/deprecated}}
 	{{name}} {{#isNullable}}*{{/isNullable}}{{{dataType}}} `json:"{{baseName}}{{^required}},omitempty{{/required}}"{{#vendorExtensions.x-go-custom-tag}} {{{.}}}{{/vendorExtensions.x-go-custom-tag}}`
 {{/vars}}
-}{{/isEnum}}
+}
+
+{{^isArray}}
+// New{{classname}}WithDefaults instantiates a new {{classname}} object
+// This constructor will only assign default values to properties that have it defined,
+// but it doesn't guarantee that properties required by API are set
+func New{{classname}}WithDefaults() {{classname}} {
+	this := {{classname}}{}
+{{#parent}}
+{{^isMap}}
+{{^isArray}}
+	this.{{{parent}}} = New{{{parent}}}WithDefaults()
+{{/isArray}}
+{{/isMap}}
+{{/parent}}
+{{#vars}}
+{{#defaultValue}}
+{{^isArray}}
+	this.{{name}} = {{#isBoolean}}{{{.}}}{{/isBoolean}}{{#isNumeric}}{{{.}}}{{/isNumeric}}{{^isBoolean}}{{^isNumeric}}"{{{.}}}"{{/isNumeric}}{{/isBoolean}}
+{{/isArray}}
+{{/defaultValue}}
+{{#isModel}}
+	{{#isNullable}}*{{/isNullable}}this.{{name}} = New{{dataType}}WithDefaults()
+{{/isModel}}
+{{/vars}}
+	return this
+}{{/isArray}}
+{{/isEnum}}
 
 // Assert{{classname}}Required checks if the required fields are not zero-ed
 func Assert{{classname}}Required(obj {{classname}}) error {

modules/openapi-generator/src/test/resources/3_0/go-server/petstore_with_test_endpoint.yaml

@@ -651,6 +651,7 @@ components:
         quantity:
           type: integer
           format: int32
+          default: 1
         shipDate:
           type: string
           format: date-time
@@ -669,6 +670,7 @@ components:
           type: string
         type:
           type: string
+          default: "dog"
       required:
         - requireTest
       xml:
@@ -687,9 +689,6 @@ components:
         petId:
           type: integer
           format: int64
-        quantity:
-          type: integer
-          format: int32
         shipDate:
           type: string
           format: date-time
@@ -700,6 +699,7 @@ components:
             - placed
             - approved
             - delivered
+          default: "placed"
         complete:
           type: boolean
           default: false

samples/openapi3/server/petstore/go/api_store_test.go

@@ -8,9 +8,10 @@ import (
 	"strings"
 	"testing"
 
+	petstoreserver "go-petstore/go"
+
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-	petstoreserver "go-petstore/go"
 )
 
 type StoreAPITestService struct {
@@ -61,9 +62,7 @@ func TestPlaceOrderOK(t *testing.T) {
 	}
 
 	// Create the controller with the service
-	router := petstoreserver.NewStoreAPIController(service)
-	controller, ok := router.(*petstoreserver.StoreAPIController)
-	require.True(t, ok)
+	controller := petstoreserver.NewStoreAPIController(service)
 
 	// Call the method of controller we are testing
 	controller.PlaceOrder(w, req)
@@ -107,9 +106,7 @@ func TestPlaceOrderFailEmbeddedRequired(t *testing.T) {
 	}
 
 	// Create the controller with the service
-	router := petstoreserver.NewStoreAPIController(service)
-	controller, ok := router.(*petstoreserver.StoreAPIController)
-	require.True(t, ok)
+	controller := petstoreserver.NewStoreAPIController(service)
 
 	// Call the method of controller we are testing
 	controller.PlaceOrder(w, req)

samples/openapi3/server/petstore/go/api_user_test.go

@@ -8,9 +8,10 @@ import (
 	"strings"
 	"testing"
 
+	petstoreserver "go-petstore/go"
+
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-	petstoreserver "go-petstore/go"
 )
 
 type UserAPITestService struct {
@@ -115,9 +116,7 @@ func TestCreateUserOK(t *testing.T) {
 	}
 
 	// Create the controller with the service
-	router := petstoreserver.NewUserAPIController(service)
-	controller, ok := router.(*petstoreserver.UserAPIController)
-	require.True(t, ok)
+	controller := petstoreserver.NewUserAPIController(service)
 
 	// Call the method of controller we are testing
 	controller.CreateUser(w, req)
@@ -214,9 +213,7 @@ func TestCreateUserOKNullablePhone(t *testing.T) {
 	}
 
 	// Create the controller with the service
-	router := petstoreserver.NewUserAPIController(service)
-	controller, ok := router.(*petstoreserver.UserAPIController)
-	require.True(t, ok)
+	controller := petstoreserver.NewUserAPIController(service)
 
 	// Call the method of controller we are testing
 	controller.CreateUser(w, req)
@@ -258,9 +255,7 @@ func TestCreateUserFailDeepSliceModelRequired(t *testing.T) {
 	}
 
 	// Create the controller with the service
-	router := petstoreserver.NewUserAPIController(service)
-	controller, ok := router.(*petstoreserver.UserAPIController)
-	require.True(t, ok)
+	controller := petstoreserver.NewUserAPIController(service)
 
 	// Call the method of controller we are testing
 	controller.CreateUser(w, req)
@@ -328,7 +323,7 @@ func TestLoginUserOK(t *testing.T) {
 		status = http.StatusOK
 	)
 
-	req := httptest.NewRequest(http.MethodPost, "/user/login?username=test&int32_test=1&int64_test=2&float32_test=1.1&float64_test=1.2&boolean_test=true", nil)
+	req := httptest.NewRequest(http.MethodPost, "/user/login?username=test&password=test&int32_test=1&int64_test=2&float32_test=1.1&float64_test=1.2&boolean_test=true", nil)
 	w := httptest.NewRecorder()
 
 	// Create the service and inject the logic
@@ -345,9 +340,7 @@ func TestLoginUserOK(t *testing.T) {
 	}
 
 	// Create the controller with the service
-	router := petstoreserver.NewUserAPIController(service)
-	controller, ok := router.(*petstoreserver.UserAPIController)
-	require.True(t, ok)
+	controller := petstoreserver.NewUserAPIController(service)
 
 	// Call the method of controller we are testing
 	controller.LoginUser(w, req)
@@ -367,7 +360,7 @@ func TestLoginUserOKOptional(t *testing.T) {
 		status = http.StatusOK
 	)
 
-	req := httptest.NewRequest(http.MethodPost, "/user/login?username=test", nil)
+	req := httptest.NewRequest(http.MethodPost, "/user/login?username=test&password=test", nil)
 	w := httptest.NewRecorder()
 
 	// Create the service and inject the logic
@@ -385,9 +378,7 @@ func TestLoginUserOKOptional(t *testing.T) {
 	}
 
 	// Create the controller with the service
-	router := petstoreserver.NewUserAPIController(service)
-	controller, ok := router.(*petstoreserver.UserAPIController)
-	require.True(t, ok)
+	controller := petstoreserver.NewUserAPIController(service)
 
 	// Call the method of controller we are testing
 	controller.LoginUser(w, req)

samples/openapi3/server/petstore/go/go-petstore/api/openapi.yaml

@@ -662,6 +662,7 @@ components:
           format: int64
           type: integer
         quantity:
+          default: 1
           format: int32
           type: integer
         shipDate:
@@ -681,6 +682,7 @@ components:
         requireTest:
           type: string
         type:
+          default: dog
           type: string
       required:
       - requireTest
@@ -695,7 +697,6 @@ components:
       description: An order for a pets from the pet store
       example:
         petId: 6
-        quantity: 1
         comment: comment
         id: 0
         shipDate: 2000-01-23T04:56:07.000+00:00
@@ -708,13 +709,11 @@ components:
         petId:
           format: int64
           type: integer
-        quantity:
-          format: int32
-          type: integer
         shipDate:
           format: date-time
           type: string
         status:
+          default: placed
           description: Order Status
           enum:
           - placed