[Go] validate required fields when unmarshalling JSON

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

@@ -479,14 +479,22 @@ public ModelsMap postProcessModels(ModelsMap objs) {
             }
 
             // additional import for different cases
+            boolean addedFmtImport = false;
+
             // oneOf
             if (model.oneOf != null && !model.oneOf.isEmpty()) {
                 imports.add(createMapping("import", "fmt"));
+                addedFmtImport = true;
             }
 
             // anyOf
             if (model.anyOf != null && !model.anyOf.isEmpty()) {
                 imports.add(createMapping("import", "fmt"));
+                addedFmtImport = true;
+            }
+
+            if (!addedFmtImport && model.hasRequired) {
+                imports.add(createMapping("import", "fmt"));
             }
 
             // additionalProperties: true and parent

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

@@ -32,6 +32,12 @@ type {{classname}} struct {
 {{#isAdditionalPropertiesTrue}}
 type _{{{classname}}} {{{classname}}}
 
+{{/isAdditionalPropertiesTrue}}
+{{^isAdditionalPropertiesTrue}}
+{{#hasRequired}}
+type _{{{classname}}} {{{classname}}}
+
+{{/hasRequired}}
 {{/isAdditionalPropertiesTrue}}
 // New{{classname}} instantiates a new {{classname}} object
 // This constructor will assign default values to properties that have it defined,
@@ -333,6 +339,38 @@ func (o {{classname}}) ToMap() (map[string]interface{}, error) {
 
 {{#isAdditionalPropertiesTrue}}
 func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {
+{{/isAdditionalPropertiesTrue}}
+{{^isAdditionalPropertiesTrue}}
+{{#hasRequired}}
+func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {
+{{/hasRequired}}
+{{/isAdditionalPropertiesTrue}}
+{{#hasRequired}}
+    // This validates that all required properties are included in the JSON object
+	// by unmarshalling the object into a generic map with string keys and checking
+	// that every required field exists as a key in the generic map.
+	requiredProperties := []string{
+{{#requiredVars}}
+		"{{baseName}}",
+{{/requiredVars}}
+	}
+
+	allProperties := make(map[string]interface{})
+
+	err = json.Unmarshal(bytes, &allProperties)
+
+	if err != nil {
+		return err;
+	}
+
+	for _, requiredProperty := range(requiredProperties) {
+		if _, exists := allProperties[requiredProperty]; !exists {
+			return fmt.Errorf("no value given for required property %v", requiredProperty)
+		}
+	}
+
+{{/hasRequired}}
+{{#isAdditionalPropertiesTrue}}
 {{#parent}}
 {{^isMap}}
 	type {{classname}}WithoutEmbeddedStruct struct {
@@ -446,8 +484,27 @@ func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {
 
 	return err
 {{/parent}}
+{{/isAdditionalPropertiesTrue}}
+{{#isAdditionalPropertiesTrue}}
+}
+
+{{/isAdditionalPropertiesTrue}}
+{{^isAdditionalPropertiesTrue}}
+{{#hasRequired}}
+	var{{{classname}}} := _{{{classname}}}{}
+
+	err = json.Unmarshal(bytes, &var{{{classname}}})
+
+	if err != nil {
+		return err
+	}
+
+	*o = {{{classname}}}(var{{{classname}}})
+
+	return err
 }
 
+{{/hasRequired}}
 {{/isAdditionalPropertiesTrue}}
 {{#isArray}}
 func (o *{{{classname}}}) UnmarshalJSON(bytes []byte) (err error) {