[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 <[email protected]>

Author: perhallgren

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

@@ -1394,23 +1394,13 @@ components:
     FilterTypeRegex:
       type: object
       properties:
-        type:
-          enum:
-          - set
-          - range
-          type: string
         regex:
           type: string
       required:
       - type
     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

@@ -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/.openapi-generator/FILES

@@ -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/README.md

@@ -1296,23 +1296,13 @@ components:
   schemas:
     FilterTypeRegex:
       properties:
-        type:
-          enum:
-          - set
-          - range
-          type: string
         regex:
           type: string
       required:
       - type
       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/api/openapi.yaml

@@ -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/FakeAPI.md

@@ -4,15 +4,16 @@
 
 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] 
 
 ## Methods
 
 ### 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/FilterAny.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/FilterTypeRange.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`