[GO] fix generated variable names when no discriminator is used with 'oneOf' (#19183)

* fix oneOf var names when no discriminator is used

* add OneOfWithComplexType to Go petstore schema

- an array of strings variant should end up with the same valid name
whether `useOneOfDiscriminatorLookup` is `true` or `false`

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

@@ -58,8 +58,8 @@ func (dst *{{classname}}) UnmarshalJSON(data []byte) error {
 	// try to unmarshal data into {{#lambda.type-to-name}}{{{.}}}{{/lambda.type-to-name}}
 	err = json.Unmarshal(data, &dst.{{#lambda.type-to-name}}{{{.}}}{{/lambda.type-to-name}})
 	if err == nil {
-		json{{{.}}}, _ := json.Marshal(dst.{{#lambda.type-to-name}}{{{.}}}{{/lambda.type-to-name}})
-		if string(json{{{.}}}) == "{}" { // empty struct
+		json{{#lambda.type-to-name}}{{{.}}}{{/lambda.type-to-name}}, _ := json.Marshal(dst.{{#lambda.type-to-name}}{{{.}}}{{/lambda.type-to-name}})
+		if string(json{{#lambda.type-to-name}}{{{.}}}{{/lambda.type-to-name}}) == "{}" { // empty struct
 			dst.{{#lambda.type-to-name}}{{{.}}}{{/lambda.type-to-name}} = nil
 		} else {
 			match++

modules/openapi-generator/src/test/resources/3_0/go/petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml

@@ -2219,3 +2219,9 @@ components:
       properties:
         id:
           type: integer
+    OneOfWithComplexType:
+      oneOf:
+        - type: string
+        - type: array
+          items:
+            type: string

samples/openapi3/client/petstore/go/go-petstore/.openapi-generator/FILES

@@ -64,6 +64,7 @@ docs/NumberOnly.md
 docs/OneOfPrimitiveType.md
 docs/OneOfPrimitiveTypeChild.md
 docs/OneOfPrimitiveTypes.md
+docs/OneOfWithComplexType.md
 docs/Order.md
 docs/OuterComposite.md
 docs/OuterEnum.md
@@ -138,6 +139,7 @@ model_number_only.go
 model_one_of_primitive_type.go
 model_one_of_primitive_type_child.go
 model_one_of_primitive_types.go
+model_one_of_with_complex_type.go
 model_order.go
 model_outer_composite.go
 model_outer_enum.go

samples/openapi3/client/petstore/go/go-petstore/README.md

@@ -177,6 +177,7 @@ Class | Method | HTTP request | Description
  - [OneOfPrimitiveType](docs/OneOfPrimitiveType.md)
  - [OneOfPrimitiveTypeChild](docs/OneOfPrimitiveTypeChild.md)
  - [OneOfPrimitiveTypes](docs/OneOfPrimitiveTypes.md)
+ - [OneOfWithComplexType](docs/OneOfWithComplexType.md)
  - [Order](docs/Order.md)
  - [OuterComposite](docs/OuterComposite.md)
  - [OuterEnum](docs/OuterEnum.md)

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

@@ -2198,6 +2198,12 @@ components:
         id:
           type: integer
       type: object
+    OneOfWithComplexType:
+      oneOf:
+      - type: string
+      - items:
+          type: string
+        type: array
     _foo_get_default_response:
       example:
         string:

samples/openapi3/client/petstore/go/go-petstore/docs/OneOfWithComplexType.md

@@ -0,0 +1,30 @@
+# OneOfWithComplexType
+
+## Properties
+
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+
+## Methods
+
+### NewOneOfWithComplexType
+
+`func NewOneOfWithComplexType() *OneOfWithComplexType`
+
+NewOneOfWithComplexType instantiates a new OneOfWithComplexType object
+This constructor will assign default values to properties that have it defined,
+and makes sure properties required by API are set, but the set of arguments
+will change when the set of required properties is changed
+
+### NewOneOfWithComplexTypeWithDefaults
+
+`func NewOneOfWithComplexTypeWithDefaults() *OneOfWithComplexType`
+
+NewOneOfWithComplexTypeWithDefaults instantiates a new OneOfWithComplexType 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
+
+
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+

samples/openapi3/client/petstore/go/go-petstore/model_one_of_with_complex_type.go

@@ -0,0 +1,157 @@
+/*
+OpenAPI Petstore
+
+This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+
+API version: 1.0.0
+*/
+
+// Code generated by OpenAPI Generator (https://openapi-generator.tech); DO NOT EDIT.
+
+package petstore
+
+import (
+	"encoding/json"
+	"gopkg.in/validator.v2"
+	"fmt"
+)
+
+// OneOfWithComplexType - struct for OneOfWithComplexType
+type OneOfWithComplexType struct {
+	ArrayOfString *[]string
+	String *string
+}
+
+// []stringAsOneOfWithComplexType is a convenience function that returns []string wrapped in OneOfWithComplexType
+func ArrayOfStringAsOneOfWithComplexType(v *[]string) OneOfWithComplexType {
+	return OneOfWithComplexType{
+		ArrayOfString: v,
+	}
+}
+
+// stringAsOneOfWithComplexType is a convenience function that returns string wrapped in OneOfWithComplexType
+func StringAsOneOfWithComplexType(v *string) OneOfWithComplexType {
+	return OneOfWithComplexType{
+		String: v,
+	}
+}
+
+
+// Unmarshal JSON data into one of the pointers in the struct
+func (dst *OneOfWithComplexType) UnmarshalJSON(data []byte) error {
+	var err error
+	match := 0
+	// try to unmarshal data into ArrayOfString
+	err = newStrictDecoder(data).Decode(&dst.ArrayOfString)
+	if err == nil {
+		jsonArrayOfString, _ := json.Marshal(dst.ArrayOfString)
+		if string(jsonArrayOfString) == "{}" { // empty struct
+			dst.ArrayOfString = nil
+		} else {
+			if err = validator.Validate(dst.ArrayOfString); err != nil {
+				dst.ArrayOfString = nil
+			} else {
+				match++
+			}
+		}
+	} else {
+		dst.ArrayOfString = nil
+	}
+
+	// try to unmarshal data into String
+	err = newStrictDecoder(data).Decode(&dst.String)
+	if err == nil {
+		jsonString, _ := json.Marshal(dst.String)
+		if string(jsonString) == "{}" { // empty struct
+			dst.String = nil
+		} else {
+			if err = validator.Validate(dst.String); err != nil {
+				dst.String = nil
+			} else {
+				match++
+			}
+		}
+	} else {
+		dst.String = nil
+	}
+
+	if match > 1 { // more than 1 match
+		// reset to nil
+		dst.ArrayOfString = nil
+		dst.String = nil
+
+		return fmt.Errorf("data matches more than one schema in oneOf(OneOfWithComplexType)")
+	} else if match == 1 {
+		return nil // exactly one match
+	} else { // no match
+		return fmt.Errorf("data failed to match schemas in oneOf(OneOfWithComplexType)")
+	}
+}
+
+// Marshal data from the first non-nil pointers in the struct to JSON
+func (src OneOfWithComplexType) MarshalJSON() ([]byte, error) {
+	if src.ArrayOfString != nil {
+		return json.Marshal(&src.ArrayOfString)
+	}
+
+	if src.String != nil {
+		return json.Marshal(&src.String)
+	}
+
+	return nil, nil // no data in oneOf schemas
+}
+
+// Get the actual instance
+func (obj *OneOfWithComplexType) GetActualInstance() (interface{}) {
+	if obj == nil {
+		return nil
+	}
+	if obj.ArrayOfString != nil {
+		return obj.ArrayOfString
+	}
+
+	if obj.String != nil {
+		return obj.String
+	}
+
+	// all schemas are nil
+	return nil
+}
+
+type NullableOneOfWithComplexType struct {
+	value *OneOfWithComplexType
+	isSet bool
+}
+
+func (v NullableOneOfWithComplexType) Get() *OneOfWithComplexType {
+	return v.value
+}
+
+func (v *NullableOneOfWithComplexType) Set(val *OneOfWithComplexType) {
+	v.value = val
+	v.isSet = true
+}
+
+func (v NullableOneOfWithComplexType) IsSet() bool {
+	return v.isSet
+}
+
+func (v *NullableOneOfWithComplexType) Unset() {
+	v.value = nil
+	v.isSet = false
+}
+
+func NewNullableOneOfWithComplexType(val *OneOfWithComplexType) *NullableOneOfWithComplexType {
+	return &NullableOneOfWithComplexType{value: val, isSet: true}
+}
+
+func (v NullableOneOfWithComplexType) MarshalJSON() ([]byte, error) {
+	return json.Marshal(v.value)
+}
+
+func (v *NullableOneOfWithComplexType) UnmarshalJSON(src []byte) error {
+	v.isSet = true
+	return json.Unmarshal(src, &v.value)
+}
+
+