[BUG][GO] use value receiver for JSON marshal (#19962)

* chore(go): add failing test for JSON marshalling

Adds a small schema (FruitJuice) which contains a required gmFruit,
which inherits using AnyOf. This fails to correctly marshal as JSON.

* fix(go): use non-pointer receiver for JSON marshal

In the case of a required anyOf property, JSON marshalling would has
been incorrect.

Required properties are not nullable, and thus always use value
receivers. For the single case of anyOf models, a pointer receiver was
used for MarshalJSON. All other instances of json marshalling use value
receivers.

This change is simply to use a value receiver instead of a pointer
receiver in the template for `MarshalJSON` on anyOf models.

---------

Co-authored-by: Per Hallgren <perhallgren@users.noreply.github.com>

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

@@ -68,7 +68,7 @@ func (dst *{{classname}}) UnmarshalJSON(data []byte) error {
 }
 
 // Marshal data from the first non-nil pointers in the struct to JSON
-func (src *{{classname}}) MarshalJSON() ([]byte, error) {
+func (src {{classname}}) MarshalJSON() ([]byte, error) {
 {{#anyOf}}
 	if src.{{#lambda.type-to-name}}{{{.}}}{{/lambda.type-to-name}} != nil {
 		return json.Marshal(&src.{{#lambda.type-to-name}}{{{.}}}{{/lambda.type-to-name}})

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

@@ -1394,11 +1394,6 @@ components:
     FilterTypeRegex:
       type: object
       properties:
-        type:
-          enum:
-          - set
-          - range
-          type: string
         regex:
           type: string
       required:
@@ -1406,11 +1401,6 @@ components:
     FilterTypeRange:
       type: object
       properties:
-        type:
-          enum:
-          - set
-          - range
-          type: string
         data:
           type: array
           items:
@@ -1425,7 +1415,16 @@ components:
         mapping:
           set: '#/components/schemas/FilterTypeRegex'
           range: '#/components/schemas/FilterTypeRange'
-        propertyName: type  
+        propertyName: type
+      properties:
+        type:
+          enum:
+          - set
+          - range
+          type: string
+        date:
+          type: string
+          format: date-time
     MapWithDateTime:
       type: object
       additionalProperties:
@@ -2119,6 +2118,13 @@ components:
           type: string
       required:
         - className
+    fruitJuice:
+      type: object
+      required:
+        - fruit
+      properties:
+        fruit:
+          $ref: '#/components/schemas/gmFruit'
     gmFruit:
        properties:
           color:

samples/client/others/go/oneof-anyof-required/model_object2.go

@@ -55,7 +55,7 @@ func (dst *Object2) UnmarshalJSON(data []byte) error {
 }
 
 // Marshal data from the first non-nil pointers in the struct to JSON
-func (src *Object2) MarshalJSON() ([]byte, error) {
+func (src Object2) MarshalJSON() ([]byte, error) {
 	if src.NestedObject1 != nil {
 		return json.Marshal(&src.NestedObject1)
 	}

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

@@ -47,6 +47,7 @@ docs/Foo.md
 docs/FooGetDefaultResponse.md
 docs/FormatTest.md
 docs/Fruit.md
+docs/FruitJuice.md
 docs/FruitReq.md
 docs/GmFruit.md
 docs/HasOnlyReadOnly.md
@@ -126,6 +127,7 @@ model_filter_type_regex.go
 model_foo.go
 model_format_test_.go
 model_fruit.go
+model_fruit_juice.go
 model_fruit_req.go
 model_gm_fruit.go
 model_has_only_read_only.go

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

@@ -161,6 +161,7 @@ Class | Method | HTTP request | Description
  - [FooGetDefaultResponse](docs/FooGetDefaultResponse.md)
  - [FormatTest](docs/FormatTest.md)
  - [Fruit](docs/Fruit.md)
+ - [FruitJuice](docs/FruitJuice.md)
  - [FruitReq](docs/FruitReq.md)
  - [GmFruit](docs/GmFruit.md)
  - [HasOnlyReadOnly](docs/HasOnlyReadOnly.md)

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

@@ -1296,11 +1296,6 @@ components:
   schemas:
     FilterTypeRegex:
       properties:
-        type:
-          enum:
-          - set
-          - range
-          type: string
         regex:
           type: string
       required:
@@ -1308,11 +1303,6 @@ components:
       type: object
     FilterTypeRange:
       properties:
-        type:
-          enum:
-          - set
-          - range
-          type: string
         data:
           items:
             type: string
@@ -1329,6 +1319,15 @@ components:
           set: '#/components/schemas/FilterTypeRegex'
           range: '#/components/schemas/FilterTypeRange'
         propertyName: type
+      properties:
+        type:
+          enum:
+          - set
+          - range
+          type: string
+        date:
+          format: date-time
+          type: string
     MapWithDateTime:
       additionalProperties:
         items:
@@ -2101,6 +2100,13 @@ components:
       required:
       - className
       type: object
+    fruitJuice:
+      properties:
+        fruit:
+          $ref: '#/components/schemas/gmFruit'
+      required:
+      - fruit
+      type: object
     gmFruit:
       anyOf:
       - $ref: '#/components/schemas/apple'

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

@@ -1197,7 +1197,7 @@ import (
 )
 
 func main() {
-	filter := *openapiclient.NewFilterAny("Type_example") // FilterAny |  (optional)
+	filter := *openapiclient.NewFilterAny() // FilterAny |  (optional)
 
 	configuration := openapiclient.NewConfiguration()
 	apiClient := openapiclient.NewAPIClient(configuration)

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

@@ -4,7 +4,8 @@
 
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
-**Type** | **string** |  | 
+**Type** | Pointer to **string** |  | [optional] 
+**Date** | Pointer to **time.Time** |  | [optional] 
 **Regex** | Pointer to **string** |  | [optional] 
 **Data** | Pointer to **[]string** |  | [optional] 
 
@@ -12,7 +13,7 @@ Name | Type | Description | Notes
 
 ### NewFilterAny
 
-`func NewFilterAny(type_ string, ) *FilterAny`
+`func NewFilterAny() *FilterAny`
 
 NewFilterAny instantiates a new FilterAny object
 This constructor will assign default values to properties that have it defined,
@@ -46,6 +47,36 @@ and a boolean to check if the value has been set.
 
 SetType sets Type field to given value.
 
+### HasType
+
+`func (o *FilterAny) HasType() bool`
+
+HasType returns a boolean if a field has been set.
+
+### GetDate
+
+`func (o *FilterAny) GetDate() time.Time`
+
+GetDate returns the Date field if non-nil, zero value otherwise.
+
+### GetDateOk
+
+`func (o *FilterAny) GetDateOk() (*time.Time, bool)`
+
+GetDateOk returns a tuple with the Date field if it's non-nil, zero value otherwise
+and a boolean to check if the value has been set.
+
+### SetDate
+
+`func (o *FilterAny) SetDate(v time.Time)`
+
+SetDate sets Date field to given value.
+
+### HasDate
+
+`func (o *FilterAny) HasDate() bool`
+
+HasDate returns a boolean if a field has been set.
 
 ### GetRegex
 

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

@@ -4,14 +4,13 @@
 
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
-**Type** | **string** |  | 
 **Data** | Pointer to **[]string** |  | [optional] 
 
 ## Methods
 
 ### NewFilterTypeRange
 
-`func NewFilterTypeRange(type_ string, ) *FilterTypeRange`
+`func NewFilterTypeRange() *FilterTypeRange`
 
 NewFilterTypeRange instantiates a new FilterTypeRange object
 This constructor will assign default values to properties that have it defined,
@@ -26,26 +25,6 @@ NewFilterTypeRangeWithDefaults instantiates a new FilterTypeRange 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
 
-### GetType
-
-`func (o *FilterTypeRange) GetType() string`
-
-GetType returns the Type field if non-nil, zero value otherwise.
-
-### GetTypeOk
-
-`func (o *FilterTypeRange) GetTypeOk() (*string, bool)`
-
-GetTypeOk returns a tuple with the Type field if it's non-nil, zero value otherwise
-and a boolean to check if the value has been set.
-
-### SetType
-
-`func (o *FilterTypeRange) SetType(v string)`
-
-SetType sets Type field to given value.
-
-
 ### GetData
 
 `func (o *FilterTypeRange) GetData() []string`

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

@@ -4,14 +4,13 @@
 
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
-**Type** | **string** |  | 
 **Regex** | Pointer to **string** |  | [optional] 
 
 ## Methods
 
 ### NewFilterTypeRegex
 
-`func NewFilterTypeRegex(type_ string, ) *FilterTypeRegex`
+`func NewFilterTypeRegex() *FilterTypeRegex`
 
 NewFilterTypeRegex instantiates a new FilterTypeRegex object
 This constructor will assign default values to properties that have it defined,
@@ -26,26 +25,6 @@ NewFilterTypeRegexWithDefaults instantiates a new FilterTypeRegex 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
 
-### GetType
-
-`func (o *FilterTypeRegex) GetType() string`
-
-GetType returns the Type field if non-nil, zero value otherwise.
-
-### GetTypeOk
-
-`func (o *FilterTypeRegex) GetTypeOk() (*string, bool)`
-
-GetTypeOk returns a tuple with the Type field if it's non-nil, zero value otherwise
-and a boolean to check if the value has been set.
-
-### SetType
-
-`func (o *FilterTypeRegex) SetType(v string)`
-
-SetType sets Type field to given value.
-
-
 ### GetRegex
 
 `func (o *FilterTypeRegex) GetRegex() string`

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

@@ -0,0 +1,51 @@
+# FruitJuice
+
+## Properties
+
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**Fruit** | [**GmFruit**](GmFruit.md) |  | 
+
+## Methods
+
+### NewFruitJuice
+
+`func NewFruitJuice(fruit GmFruit, ) *FruitJuice`
+
+NewFruitJuice instantiates a new FruitJuice 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
+
+### NewFruitJuiceWithDefaults
+
+`func NewFruitJuiceWithDefaults() *FruitJuice`
+
+NewFruitJuiceWithDefaults instantiates a new FruitJuice 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
+
+### GetFruit
+
+`func (o *FruitJuice) GetFruit() GmFruit`
+
+GetFruit returns the Fruit field if non-nil, zero value otherwise.
+
+### GetFruitOk
+
+`func (o *FruitJuice) GetFruitOk() (*GmFruit, bool)`
+
+GetFruitOk returns a tuple with the Fruit field if it's non-nil, zero value otherwise
+and a boolean to check if the value has been set.
+
+### SetFruit
+
+`func (o *FruitJuice) SetFruit(v GmFruit)`
+
+SetFruit sets Fruit field to given value.
+
+
+
+[[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_any_of_primitive_type.go

@@ -69,7 +69,7 @@ func (dst *AnyOfPrimitiveType) UnmarshalJSON(data []byte) error {
 }
 
 // Marshal data from the first non-nil pointers in the struct to JSON
-func (src *AnyOfPrimitiveType) MarshalJSON() ([]byte, error) {
+func (src AnyOfPrimitiveType) MarshalJSON() ([]byte, error) {
 	if src.OneOfPrimitiveTypeChild != nil {
 		return json.Marshal(&src.OneOfPrimitiveTypeChild)
 	}

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

@@ -128,7 +128,7 @@ func (dst *FilterAny) UnmarshalJSON(data []byte) error {
 }
 
 // Marshal data from the first non-nil pointers in the struct to JSON
-func (src *FilterAny) MarshalJSON() ([]byte, error) {
+func (src FilterAny) MarshalJSON() ([]byte, error) {
 	if src.FilterTypeRange != nil {
 		return json.Marshal(&src.FilterTypeRange)
 	}

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

@@ -12,7 +12,6 @@ package petstore
 
 import (
 	"encoding/json"
-	"fmt"
 )
 
 // checks if the FilterTypeRange type satisfies the MappedNullable interface at compile time
@@ -20,7 +19,6 @@ var _ MappedNullable = &FilterTypeRange{}
 
 // FilterTypeRange struct for FilterTypeRange
 type FilterTypeRange struct {
-	Type string `json:"type"`
 	Data []string `json:"data,omitempty"`
 	AdditionalProperties map[string]interface{}
 }
@@ -31,9 +29,8 @@ type _FilterTypeRange FilterTypeRange
 // 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
-func NewFilterTypeRange(type_ string) *FilterTypeRange {
+func NewFilterTypeRange() *FilterTypeRange {
 	this := FilterTypeRange{}
-	this.Type = type_
 	return &this
 }
 
@@ -45,31 +42,6 @@ func NewFilterTypeRangeWithDefaults() *FilterTypeRange {
 	return &this
 }
 
-// GetType returns the Type field value
-func (o *FilterTypeRange) GetType() string {
-	if o == nil {
-		var ret string
-		return ret
-	}
-
-	return o.Type
-}
-
-// GetTypeOk returns a tuple with the Type field value
-// and a boolean to check if the value has been set.
-func (o *FilterTypeRange) GetTypeOk() (*string, bool) {
-	if o == nil {
-		return nil, false
-	}
-	return &o.Type, true
-}
-
-// SetType sets field value
-func (o *FilterTypeRange) SetType(v string) {
-	o.Type = v
-}
-
-
 // GetData returns the Data field value if set, zero value otherwise.
 func (o *FilterTypeRange) GetData() []string {
 	if o == nil || IsNil(o.Data) {
@@ -112,7 +84,6 @@ func (o FilterTypeRange) MarshalJSON() ([]byte, error) {
 
 func (o FilterTypeRange) ToMap() (map[string]interface{}, error) {
 	toSerialize := map[string]interface{}{}
-	toSerialize["type"] = o.Type
 	if !IsNil(o.Data) {
 		toSerialize["data"] = o.Data
 	}
@@ -125,44 +96,6 @@ func (o FilterTypeRange) ToMap() (map[string]interface{}, error) {
 }
 
 func (o *FilterTypeRange) UnmarshalJSON(data []byte) (err error) {
-	// 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{
-		"type",
-	}
-
-	// defaultValueFuncMap captures the default values for required properties.
-	// These values are used when required properties are missing from the payload.
-	defaultValueFuncMap := map[string]func() interface{} {
-	}
-	var defaultValueApplied bool
-	allProperties := make(map[string]interface{})
-
-	err = json.Unmarshal(data, &allProperties)
-
-	if err != nil {
-		return err;
-	}
-
-	for _, requiredProperty := range(requiredProperties) {
-		if value, exists := allProperties[requiredProperty]; !exists || value == "" {
-			if _, ok := defaultValueFuncMap[requiredProperty]; ok {
-				allProperties[requiredProperty] = defaultValueFuncMap[requiredProperty]()
-				defaultValueApplied = true
-			}
-		}
-		if value, exists := allProperties[requiredProperty]; !exists || value == ""{
-			return fmt.Errorf("no value given for required property %v", requiredProperty)
-		}
-	}
-
-	if defaultValueApplied {
-		data, err = json.Marshal(allProperties)
-		if err != nil{
-			return err
-		}
-	}
 	varFilterTypeRange := _FilterTypeRange{}
 
 	err = json.Unmarshal(data, &varFilterTypeRange)
@@ -176,7 +109,6 @@ func (o *FilterTypeRange) UnmarshalJSON(data []byte) (err error) {
 	additionalProperties := make(map[string]interface{})
 
 	if err = json.Unmarshal(data, &additionalProperties); err == nil {
-		delete(additionalProperties, "type")
 		delete(additionalProperties, "data")
 		o.AdditionalProperties = additionalProperties
 	}

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

@@ -12,7 +12,6 @@ package petstore
 
 import (
 	"encoding/json"
-	"fmt"
 )
 
 // checks if the FilterTypeRegex type satisfies the MappedNullable interface at compile time
@@ -20,7 +19,6 @@ var _ MappedNullable = &FilterTypeRegex{}
 
 // FilterTypeRegex struct for FilterTypeRegex
 type FilterTypeRegex struct {
-	Type string `json:"type"`
 	Regex *string `json:"regex,omitempty"`
 	AdditionalProperties map[string]interface{}
 }
@@ -31,9 +29,8 @@ type _FilterTypeRegex FilterTypeRegex
 // 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
-func NewFilterTypeRegex(type_ string) *FilterTypeRegex {
+func NewFilterTypeRegex() *FilterTypeRegex {
 	this := FilterTypeRegex{}
-	this.Type = type_
 	return &this
 }
 
@@ -45,31 +42,6 @@ func NewFilterTypeRegexWithDefaults() *FilterTypeRegex {
 	return &this
 }
 
-// GetType returns the Type field value
-func (o *FilterTypeRegex) GetType() string {
-	if o == nil {
-		var ret string
-		return ret
-	}
-
-	return o.Type
-}
-
-// GetTypeOk returns a tuple with the Type field value
-// and a boolean to check if the value has been set.
-func (o *FilterTypeRegex) GetTypeOk() (*string, bool) {
-	if o == nil {
-		return nil, false
-	}
-	return &o.Type, true
-}
-
-// SetType sets field value
-func (o *FilterTypeRegex) SetType(v string) {
-	o.Type = v
-}
-
-
 // GetRegex returns the Regex field value if set, zero value otherwise.
 func (o *FilterTypeRegex) GetRegex() string {
 	if o == nil || IsNil(o.Regex) {
@@ -112,7 +84,6 @@ func (o FilterTypeRegex) MarshalJSON() ([]byte, error) {
 
 func (o FilterTypeRegex) ToMap() (map[string]interface{}, error) {
 	toSerialize := map[string]interface{}{}
-	toSerialize["type"] = o.Type
 	if !IsNil(o.Regex) {
 		toSerialize["regex"] = o.Regex
 	}
@@ -125,44 +96,6 @@ func (o FilterTypeRegex) ToMap() (map[string]interface{}, error) {
 }
 
 func (o *FilterTypeRegex) UnmarshalJSON(data []byte) (err error) {
-	// 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{
-		"type",
-	}
-
-	// defaultValueFuncMap captures the default values for required properties.
-	// These values are used when required properties are missing from the payload.
-	defaultValueFuncMap := map[string]func() interface{} {
-	}
-	var defaultValueApplied bool
-	allProperties := make(map[string]interface{})
-
-	err = json.Unmarshal(data, &allProperties)
-
-	if err != nil {
-		return err;
-	}
-
-	for _, requiredProperty := range(requiredProperties) {
-		if value, exists := allProperties[requiredProperty]; !exists || value == "" {
-			if _, ok := defaultValueFuncMap[requiredProperty]; ok {
-				allProperties[requiredProperty] = defaultValueFuncMap[requiredProperty]()
-				defaultValueApplied = true
-			}
-		}
-		if value, exists := allProperties[requiredProperty]; !exists || value == ""{
-			return fmt.Errorf("no value given for required property %v", requiredProperty)
-		}
-	}
-
-	if defaultValueApplied {
-		data, err = json.Marshal(allProperties)
-		if err != nil{
-			return err
-		}
-	}
 	varFilterTypeRegex := _FilterTypeRegex{}
 
 	err = json.Unmarshal(data, &varFilterTypeRegex)
@@ -176,7 +109,6 @@ func (o *FilterTypeRegex) UnmarshalJSON(data []byte) (err error) {
 	additionalProperties := make(map[string]interface{})
 
 	if err = json.Unmarshal(data, &additionalProperties); err == nil {
-		delete(additionalProperties, "type")
 		delete(additionalProperties, "regex")
 		o.AdditionalProperties = additionalProperties
 	}

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

@@ -0,0 +1,186 @@
+/*
+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"
+	"fmt"
+)
+
+// checks if the FruitJuice type satisfies the MappedNullable interface at compile time
+var _ MappedNullable = &FruitJuice{}
+
+// FruitJuice struct for FruitJuice
+type FruitJuice struct {
+	Fruit GmFruit `json:"fruit"`
+	AdditionalProperties map[string]interface{}
+}
+
+type _FruitJuice FruitJuice
+
+// NewFruitJuice instantiates a new FruitJuice 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
+func NewFruitJuice(fruit GmFruit) *FruitJuice {
+	this := FruitJuice{}
+	this.Fruit = fruit
+	return &this
+}
+
+// NewFruitJuiceWithDefaults instantiates a new FruitJuice 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 NewFruitJuiceWithDefaults() *FruitJuice {
+	this := FruitJuice{}
+	return &this
+}
+
+// GetFruit returns the Fruit field value
+func (o *FruitJuice) GetFruit() GmFruit {
+	if o == nil {
+		var ret GmFruit
+		return ret
+	}
+
+	return o.Fruit
+}
+
+// GetFruitOk returns a tuple with the Fruit field value
+// and a boolean to check if the value has been set.
+func (o *FruitJuice) GetFruitOk() (*GmFruit, bool) {
+	if o == nil {
+		return nil, false
+	}
+	return &o.Fruit, true
+}
+
+// SetFruit sets field value
+func (o *FruitJuice) SetFruit(v GmFruit) {
+	o.Fruit = v
+}
+
+
+func (o FruitJuice) MarshalJSON() ([]byte, error) {
+	toSerialize,err := o.ToMap()
+	if err != nil {
+		return []byte{}, err
+	}
+	return json.Marshal(toSerialize)
+}
+
+func (o FruitJuice) ToMap() (map[string]interface{}, error) {
+	toSerialize := map[string]interface{}{}
+	toSerialize["fruit"] = o.Fruit
+
+	for key, value := range o.AdditionalProperties {
+		toSerialize[key] = value
+	}
+
+	return toSerialize, nil
+}
+
+func (o *FruitJuice) UnmarshalJSON(data []byte) (err error) {
+	// 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{
+		"fruit",
+	}
+
+	// defaultValueFuncMap captures the default values for required properties.
+	// These values are used when required properties are missing from the payload.
+	defaultValueFuncMap := map[string]func() interface{} {
+	}
+	var defaultValueApplied bool
+	allProperties := make(map[string]interface{})
+
+	err = json.Unmarshal(data, &allProperties)
+
+	if err != nil {
+		return err;
+	}
+
+	for _, requiredProperty := range(requiredProperties) {
+		if value, exists := allProperties[requiredProperty]; !exists || value == "" {
+			if _, ok := defaultValueFuncMap[requiredProperty]; ok {
+				allProperties[requiredProperty] = defaultValueFuncMap[requiredProperty]()
+				defaultValueApplied = true
+			}
+		}
+		if value, exists := allProperties[requiredProperty]; !exists || value == ""{
+			return fmt.Errorf("no value given for required property %v", requiredProperty)
+		}
+	}
+
+	if defaultValueApplied {
+		data, err = json.Marshal(allProperties)
+		if err != nil{
+			return err
+		}
+	}
+	varFruitJuice := _FruitJuice{}
+
+	err = json.Unmarshal(data, &varFruitJuice)
+
+	if err != nil {
+		return err
+	}
+
+	*o = FruitJuice(varFruitJuice)
+
+	additionalProperties := make(map[string]interface{})
+
+	if err = json.Unmarshal(data, &additionalProperties); err == nil {
+		delete(additionalProperties, "fruit")
+		o.AdditionalProperties = additionalProperties
+	}
+
+	return err
+}
+
+type NullableFruitJuice struct {
+	value *FruitJuice
+	isSet bool
+}
+
+func (v NullableFruitJuice) Get() *FruitJuice {
+	return v.value
+}
+
+func (v *NullableFruitJuice) Set(val *FruitJuice) {
+	v.value = val
+	v.isSet = true
+}
+
+func (v NullableFruitJuice) IsSet() bool {
+	return v.isSet
+}
+
+func (v *NullableFruitJuice) Unset() {
+	v.value = nil
+	v.isSet = false
+}
+
+func NewNullableFruitJuice(val *FruitJuice) *NullableFruitJuice {
+	return &NullableFruitJuice{value: val, isSet: true}
+}
+
+func (v NullableFruitJuice) MarshalJSON() ([]byte, error) {
+	return json.Marshal(v.value)
+}
+
+func (v *NullableFruitJuice) UnmarshalJSON(src []byte) error {
+	v.isSet = true
+	return json.Unmarshal(src, &v.value)
+}
+
+

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

@@ -55,7 +55,7 @@ func (dst *GmFruit) UnmarshalJSON(data []byte) error {
 }
 
 // Marshal data from the first non-nil pointers in the struct to JSON
-func (src *GmFruit) MarshalJSON() ([]byte, error) {
+func (src GmFruit) MarshalJSON() ([]byte, error) {
 	if src.Apple != nil {
 		return json.Marshal(&src.Apple)
 	}

samples/openapi3/client/petstore/go/go.mod

@@ -6,10 +6,10 @@ replace go-petstore => ./go-petstore
 
 require (
 	cloud.google.com/go/compute v1.20.1 // indirect
-	github.com/stretchr/testify v1.9.0
+	github.com/stretchr/testify v1.10.0
 	go-petstore v0.0.0-00010101000000-000000000000
-	golang.org/x/net v0.27.0 // indirect
-	golang.org/x/oauth2 v0.21.0
+	golang.org/x/net v0.31.0 // indirect
+	golang.org/x/oauth2 v0.24.0
 	google.golang.org/protobuf v1.31.0 // indirect
 	gopkg.in/validator.v2 v2.0.1 // indirect
 )

samples/openapi3/client/petstore/go/go.sum

@@ -859,6 +859,8 @@ github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcU
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
+github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 github.com/yuin/goldmark v1.1.25/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.1.32/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
@@ -898,6 +900,7 @@ golang.org/x/crypto v0.18.0/go.mod h1:R0j02AL6hcrfOiy9T4ZYp/rcWeMxM3L6QYxlOuEG1m
 golang.org/x/crypto v0.19.0/go.mod h1:Iy9bg/ha4yyC70EfRS8jz+B6ybOBKMaSxLj6P6oBDfU=
 golang.org/x/crypto v0.23.0/go.mod h1:CKFgDieR+mRhux2Lsu27y0fO304Db0wZe70UKqHu0v8=
 golang.org/x/crypto v0.25.0/go.mod h1:T+wALwcMOSE0kXgUAnPAHqTLW+XHgcELELW8VaDgm/M=
+golang.org/x/crypto v0.29.0/go.mod h1:+F4F4N5hv6v38hfeYwTdx20oUvLLc+QfrE9Ax9HtgRg=
 golang.org/x/exp v0.0.0-20180321215751-8460e604b9de/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20180807140117-3d87b88a115f/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
@@ -1040,6 +1043,8 @@ golang.org/x/net v0.25.0 h1:d/OCCoBEUq33pjydKrGQhw7IlUPI2Oylr+8qLx49kac=
 golang.org/x/net v0.25.0/go.mod h1:JkAGAh7GEvH74S6FOH42FLoXpXbE/aqXSrIQjXgsiwM=
 golang.org/x/net v0.27.0 h1:5K3Njcw06/l2y9vpGCSdcxWOYHOUk3dVNGDXN+FvAys=
 golang.org/x/net v0.27.0/go.mod h1:dDi0PyhWNoiUOrAS8uXv/vnScO4wnHQO4mj9fn/RytE=
+golang.org/x/net v0.31.0 h1:68CPQngjLL0r2AlUKiSxtQFKvzRVbnzLwMUn5SzcLHo=
+golang.org/x/net v0.31.0/go.mod h1:P4fl1q7dY2hnZFxEk4pPSkDHF+QqjitcnDjUQyMM+pM=
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/oauth2 v0.0.0-20190226205417-e64efc72b421/go.mod h1:gOpvHmFTYa4IltrdGE7lF6nIHvwfUNPOp7c8zoXwtLw=
 golang.org/x/oauth2 v0.0.0-20190604053449-0f29369cfe45/go.mod h1:gOpvHmFTYa4IltrdGE7lF6nIHvwfUNPOp7c8zoXwtLw=
@@ -1087,6 +1092,8 @@ golang.org/x/oauth2 v0.20.0 h1:4mQdhULixXKP1rwYBW0vAijoXnkTG0BLCDRzfe1idMo=
 golang.org/x/oauth2 v0.20.0/go.mod h1:XYTD2NtWslqkgxebSiOHnXEap4TF09sJSc7H1sXbhtI=
 golang.org/x/oauth2 v0.21.0 h1:tsimM75w1tF/uws5rbeHzIWxEqElMehnc+iW793zsZs=
 golang.org/x/oauth2 v0.21.0/go.mod h1:XYTD2NtWslqkgxebSiOHnXEap4TF09sJSc7H1sXbhtI=
+golang.org/x/oauth2 v0.24.0 h1:KTBBxWqUa0ykRPLtV69rRto9TLXcqYkeswu48x/gvNE=
+golang.org/x/oauth2 v0.24.0/go.mod h1:XYTD2NtWslqkgxebSiOHnXEap4TF09sJSc7H1sXbhtI=
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
@@ -1107,6 +1114,7 @@ golang.org/x/sync v0.2.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.3.0/go.mod h1:FU7BRWz2tNW+3quACPkgCx/L+uEAv1htQ0V83Z9Rj+Y=
 golang.org/x/sync v0.6.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sync v0.7.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
+golang.org/x/sync v0.9.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190312061237-fead79001313/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
@@ -1192,6 +1200,7 @@ golang.org/x/sys v0.16.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/sys v0.17.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/sys v0.20.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/sys v0.22.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.27.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/telemetry v0.0.0-20240228155512-f48c80bd79b2/go.mod h1:TeRTkGYfJXctD9OcfyVLyj2J3IxLnKwHJR8f4D8a3YE=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
@@ -1209,6 +1218,7 @@ golang.org/x/term v0.16.0/go.mod h1:yn7UURbUtPyrVJPGPq404EukNFxcm/foM+bV/bfcDsY=
 golang.org/x/term v0.17.0/go.mod h1:lLRBjIVuehSbZlaOtGMbcMncT+aqLLLmKrsjNrUguwk=
 golang.org/x/term v0.20.0/go.mod h1:8UkIAJTvZgivsXaD6/pH6U9ecQzZ45awqEOzuCvwpFY=
 golang.org/x/term v0.22.0/go.mod h1:F3qCibpT5AMpCRfhfT53vVJwhLtIVHhB9XDjfFvnMI4=
+golang.org/x/term v0.26.0/go.mod h1:Si5m1o57C5nBNQo5z1iq+XDijt21BDBDp2bK0QI8e3E=
 golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.1-0.20180807135948-17ff2d5776d2/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
@@ -1230,6 +1240,7 @@ golang.org/x/text v0.13.0/go.mod h1:TvPlkZtksWOMsz7fbANvkp4WM8x/WCo/om8BMLbz+aE=
 golang.org/x/text v0.14.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
 golang.org/x/text v0.15.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
 golang.org/x/text v0.16.0/go.mod h1:GhwF1Be+LQoKShO3cGOHzqOgRrGaYc9AvblQOmPVHnI=
+golang.org/x/text v0.20.0/go.mod h1:D4IsuqiFMhST5bX19pQ9ikHC2GsaKyk/oF+pn3ducp4=
 golang.org/x/time v0.0.0-20181108054448-85acf8d2951c/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/time v0.0.0-20190308202827-9d24e82272b4/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/time v0.0.0-20191024005414-555d28b269f0/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=

samples/openapi3/client/petstore/go/model_test.go

@@ -1,7 +1,9 @@
 package main
 
 import (
+	"bytes"
 	"encoding/json"
+	"strings"
 	"testing"
 
 	sw "go-petstore"
@@ -63,3 +65,19 @@ func TestRequiredFieldsAreValidated(t *testing.T) {
 
 	assert.ErrorContains(err, expected, "Pet should return error when missing required fields")
 }
+
+func TestRequiredAnyOfMarshalling(t *testing.T) {
+	// Given
+	bodyBuf := &bytes.Buffer{}
+	bananaLengthCm := float32(23.4)
+	req := &sw.FruitJuice{Fruit: sw.GmFruit{
+		Banana: &sw.Banana{LengthCm: &bananaLengthCm},
+	}}
+
+	// When
+	err := json.NewEncoder(bodyBuf).Encode(req)
+
+	// Then
+	assert.Nil(t, err)
+	assert.Equal(t, strings.TrimSpace(bodyBuf.String()), "{\"fruit\":{\"lengthCm\":23.4}}")
+}