[Go] fix validation of property names when a model has required fields and doesn't allow additional properties (#17267)

* update template for required field validation when additional properties are not allowed

* regenerate samples

* move bytes import from template to GoClientCodegen

* regenerate samples

* add test for model with required fields and additionalProperties: false

Author: ctreatma

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientCodegen.java

@@ -499,8 +499,14 @@ public ModelsMap postProcessModels(ModelsMap objs) {
                 addedFmtImport = true;
             }
 
-            if (!addedFmtImport && model.hasRequired) {
-                imports.add(createMapping("import", "fmt"));
+            if (model.hasRequired) {
+                if (!model.isAdditionalPropertiesTrue) {
+                    imports.add(createMapping("import", "bytes"));
+                }
+
+                if (!addedFmtImport) {
+                    imports.add(createMapping("import", "fmt"));
+                }
             }
 
             // additionalProperties: true and parent

modules/openapi-generator/src/main/resources/go/model_simple.mustache

@@ -340,11 +340,11 @@ func (o {{classname}}) ToMap() (map[string]interface{}, error) {
 }
 
 {{#isAdditionalPropertiesTrue}}
-func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {
+func (o *{{{classname}}}) UnmarshalJSON(data []byte) (err error) {
 {{/isAdditionalPropertiesTrue}}
 {{^isAdditionalPropertiesTrue}}
 {{#hasRequired}}
-func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {
+func (o *{{{classname}}}) UnmarshalJSON(data []byte) (err error) {
 {{/hasRequired}}
 {{/isAdditionalPropertiesTrue}}
 {{#hasRequired}}
@@ -359,7 +359,7 @@ func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {
 
 	allProperties := make(map[string]interface{})
 
-	err = json.Unmarshal(bytes, &allProperties)
+	err = json.Unmarshal(data, &allProperties)
 
 	if err != nil {
 		return err;
@@ -391,7 +391,7 @@ func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {
 
 	var{{{classname}}}WithoutEmbeddedStruct := {{{classname}}}WithoutEmbeddedStruct{}
 
-	err = json.Unmarshal(bytes, &var{{{classname}}}WithoutEmbeddedStruct)
+	err = json.Unmarshal(data, &var{{{classname}}}WithoutEmbeddedStruct)
 	if err == nil {
 		var{{{classname}}} := _{{{classname}}}{}
 		{{#vars}}
@@ -404,7 +404,7 @@ func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {
 
 	var{{{classname}}} := _{{{classname}}}{}
 
-	err = json.Unmarshal(bytes, &var{{{classname}}})
+	err = json.Unmarshal(data, &var{{{classname}}})
 	if err == nil {
 		o.{{{parent}}} = var{{{classname}}}.{{{parent}}}
 	} else {
@@ -413,7 +413,7 @@ func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {
 
 	additionalProperties := make(map[string]interface{})
 
-	if err = json.Unmarshal(bytes, &additionalProperties); err == nil {
+	if err = json.Unmarshal(data, &additionalProperties); err == nil {
 		{{#vars}}
 		delete(additionalProperties, "{{{baseName}}}")
 		{{/vars}}
@@ -444,7 +444,7 @@ func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {
 {{#isMap}}
 	var{{{classname}}} := _{{{classname}}}{}
 
-	err = json.Unmarshal(bytes, &var{{{classname}}})
+	err = json.Unmarshal(data, &var{{{classname}}})
 
 	if err != nil {
 		return err
@@ -454,7 +454,7 @@ func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {
 
 	additionalProperties := make(map[string]interface{})
 
-	if err = json.Unmarshal(bytes, &additionalProperties); err == nil {
+	if err = json.Unmarshal(data, &additionalProperties); err == nil {
 		{{#vars}}
 		delete(additionalProperties, "{{{baseName}}}")
 		{{/vars}}
@@ -467,7 +467,7 @@ func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {
 {{^parent}}
 	var{{{classname}}} := _{{{classname}}}{}
 
-	err = json.Unmarshal(bytes, &var{{{classname}}})
+	err = json.Unmarshal(data, &var{{{classname}}})
 
 	if err != nil {
 		return err
@@ -477,7 +477,7 @@ func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {
 
 	additionalProperties := make(map[string]interface{})
 
-	if err = json.Unmarshal(bytes, &additionalProperties); err == nil {
+	if err = json.Unmarshal(data, &additionalProperties); err == nil {
 		{{#vars}}
 		delete(additionalProperties, "{{{baseName}}}")
 		{{/vars}}
@@ -495,7 +495,9 @@ func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {
 {{#hasRequired}}
 	var{{{classname}}} := _{{{classname}}}{}
 
-	err = json.Unmarshal(bytes, &var{{{classname}}})
+	decoder := json.NewDecoder(bytes.NewReader(data))
+	decoder.DisallowUnknownFields()
+	err = decoder.Decode(&var{{{classname}}})
 
 	if err != nil {
 		return err
@@ -509,8 +511,8 @@ func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {
 {{/hasRequired}}
 {{/isAdditionalPropertiesTrue}}
 {{#isArray}}
-func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {
-	return json.Unmarshal(bytes, &o.Items)
+func (o *{{{classname}}}) UnmarshalJSON(data []byte) (err error) {
+	return json.Unmarshal(data, &o.Items)
 }
 
 {{/isArray}}