feat!: add convert functions for toplevel oneofs. (#41)

* add convert functions for toplevel oneofs.

Signed-off-by: Tino Rusch <tino.rusch@gmail.com>

Author: trusch

go.mod

@@ -5,6 +5,7 @@ go 1.16
 require (
 	github.com/getkin/kin-openapi v0.14.0
 	github.com/mitchellh/go-homedir v1.1.0
+	github.com/mitchellh/mapstructure v1.4.1 // indirect
 	github.com/pkg/errors v0.8.1
 	github.com/rs/zerolog v1.20.0
 	github.com/spf13/cobra v1.1.1

go.sum

@@ -129,6 +129,8 @@ github.com/mitchellh/iochan v1.0.0/go.mod h1:JwYml1nuB7xOzsp52dPpHFffvOCDupsG0Qu
 github.com/mitchellh/mapstructure v0.0.0-20160808181253-ca63d7c062ee/go.mod h1:FVVH3fgwuzCH5S8UJGiWEs2h04kUh9fWfEaFds41c1Y=
 github.com/mitchellh/mapstructure v1.1.2 h1:fmNYVwqnSfB9mZU6OS2O6GsXM+wcskZDuKQzvN1EDeE=
 github.com/mitchellh/mapstructure v1.1.2/go.mod h1:FVVH3fgwuzCH5S8UJGiWEs2h04kUh9fWfEaFds41c1Y=
+github.com/mitchellh/mapstructure v1.4.1 h1:CpVNEelQCZBooIPDn+AR3NpivK/TIKU8bDxdASFVQag=
+github.com/mitchellh/mapstructure v1.4.1/go.mod h1:bFUtVrKA4DC2yAKiSyO/QUcy7e+RRV2QTWOzhPopBRo=
 github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=
 github.com/modern-go/reflect2 v1.0.1/go.mod h1:bx2lNnkwVCuqBIxFjflWJWanXIb3RllmbCylyMrvgv0=
 github.com/mwitkow/go-conntrack v0.0.0-20161129095857-cc309e4a2223/go.mod h1:qRWi+5nqEBWmkhHvq77mSJWrCKwh8bxhgT7d/eI7P4U=

pkg/generators/models/models.go

@@ -40,6 +40,8 @@ const (
 	Enum ModelKind = "enum"
 	// Value is a value type
 	Value ModelKind = "value"
+	// OneOf is a oneof value
+	OneOf ModelKind = "oneof"
 )
 
 // Model is a template model for rendering Go code for a given API schema
@@ -55,6 +57,8 @@ type Model struct {
 	Kind ModelKind
 	// Properties is a list of type's property descriptors
 	Properties []PropSpec
+	// ConvertSpecs contains a list of convert functions for this model
+	ConvertSpecs []ConvertSpec
 	// GoType is a string that represents the Go type that follows the model type name.
 	// For example, `type Name GoType`.
 	GoType string
@@ -66,6 +70,12 @@ type Model struct {
 	PackageName string
 }
 
+// ConvertSpec holds all info to build one As{Type}() function
+type ConvertSpec struct {
+	// TargetGoType is the target type of the conversion
+	TargetGoType string
+}
+
 // PropSpec is a Go property descriptor
 type PropSpec struct {
 	// Name is a property name in structs, variable name in enums, etc
@@ -131,6 +141,9 @@ func NewModelFromRef(ref *openapi3.SchemaRef) (model *Model, err error) {
 				model.GoType = "map[string]" + goTypeFromSpec(ref.Value.AdditionalProperties)
 			}
 		}
+	case len(ref.Value.OneOf) > 0:
+		model.Kind = OneOf
+		model.fillConvertSpecs(ref)
 	default:
 		model.Kind = Value
 		model.GoType = goTypeFromSpec(ref)
@@ -176,6 +189,15 @@ func NewModelFromParameters(params openapi3.Parameters) (model *Model, err error
 	return model, nil
 }
 
+func (m *Model) fillConvertSpecs(ref *openapi3.SchemaRef) {
+	for _, oneOf := range ref.Value.OneOf {
+		m.ConvertSpecs = append(m.ConvertSpecs, ConvertSpec{
+			TargetGoType: goTypeFromSpec(oneOf),
+		})
+	}
+
+}
+
 // Render renders the model to a Go file
 func (m *Model) Render(ctx context.Context, writer io.Writer) error {
 	var tpl *template.Template
@@ -187,6 +209,8 @@ func (m *Model) Render(ctx context.Context, writer io.Writer) error {
 		tpl = enumTemplate
 	case Value:
 		tpl = valueTemplate
+	case OneOf:
+		tpl = oneOfTemplate
 	}
 
 	err := tpl.Execute(writer, m)

pkg/generators/models/templates.go

@@ -25,6 +25,12 @@ var (
 			Parse(valueTemplateSource),
 	)
 
+	oneOfTemplate = template.Must(
+		template.New("oneof").
+			Funcs(fmap).
+			Parse(oneOfTemplateSource),
+	)
+
 	fmap = template.FuncMap{
 		"firstLower":   tpl.FirstLower,
 		"firstUpper":   tpl.FirstUpper,
@@ -150,6 +156,50 @@ var (
 		{{- end}}
 	)
 )
+`
+
+	oneOfTemplateSource = `
+// This file is auto-generated, DO NOT EDIT.
+//
+// Source:
+//     Title: {{.SpecTitle}}
+//     Version: {{.SpecVersion}}
+package {{ .PackageName }}
+
+import (
+	"encoding/json"
+	"github.com/mitchellh/mapstructure"
+)
+
+{{ (printf "%s is a oneOf type. %s" .Name .Description) | commentBlock }}
+type {{.Name}} struct {
+	data interface{}
+}
+
+{{- $modelName := .Name }}
+
+// MarshalJSON implementes the json.Marshaller interface
+func (m *{{$modelName}}) MarshalJSON() ([]byte, error) {
+	return json.Marshal(m.data)
+}
+
+// UnmarshalJSON implementes the json.Unmarshaller interface
+func (m *{{$modelName}}) UnmarshalJSON(bs []byte) error {
+	return json.Unmarshal(bs, &m.data)
+}
+
+// As converts {{$modelName}} to a user defined structure.
+func (m {{$modelName}}) As(target interface{}) error {
+	return mapstructure.Decode(m.data, target)
+}
+
+{{- range $convert := .ConvertSpecs }}
+// As{{firstUpper $convert.TargetGoType}} converts {{$modelName}} to a {{$convert.TargetGoType}}
+func (m {{$modelName}}) As{{firstUpper $convert.TargetGoType}}() (result {{$convert.TargetGoType}}, err error) {
+	return result, mapstructure.Decode(m.data, &result)
+}
+
+{{- end}}
 `
 
 	valueTemplateSource = `

pkg/generators/models/testdata/cases/oneof/api.yaml

@@ -17,3 +17,16 @@ components:
         - type: string
         - type: integer
 
+    Baz:
+      oneOf:
+        - $ref: "#/components/schemas/Foo"
+        - $ref: "#/components/schemas/Bar"
+        - $ref: "#/components/schemas/Person"
+
+    Person:
+      type: object
+      properties:
+        name: 
+          type: string
+        age:
+          type: integer

pkg/generators/models/testdata/cases/oneof/expected/model_bar.go

@@ -5,5 +5,37 @@
 //     Version: 0.1.0
 package generatortest
 
-// Bar is a value type.
-type Bar interface{}
+import (
+	"encoding/json"
+	"github.com/mitchellh/mapstructure"
+)
+
+// Bar is a oneOf type.
+type Bar struct {
+	data interface{}
+}
+
+// MarshalJSON implementes the json.Marshaller interface
+func (m *Bar) MarshalJSON() ([]byte, error) {
+	return json.Marshal(m.data)
+}
+
+// UnmarshalJSON implementes the json.Unmarshaller interface
+func (m *Bar) UnmarshalJSON(bs []byte) error {
+	return json.Unmarshal(bs, &m.data)
+}
+
+// As converts Bar to a user defined structure.
+func (m Bar) As(target interface{}) error {
+	return mapstructure.Decode(m.data, target)
+}
+
+// AsString converts Bar to a string
+func (m Bar) AsString() (result string, err error) {
+	return result, mapstructure.Decode(m.data, &result)
+}
+
+// AsInt32 converts Bar to a int32
+func (m Bar) AsInt32() (result int32, err error) {
+	return result, mapstructure.Decode(m.data, &result)
+}

pkg/generators/models/testdata/cases/oneof/expected/model_baz.go

@@ -0,0 +1,46 @@
+// This file is auto-generated, DO NOT EDIT.
+//
+// Source:
+//     Title: Test
+//     Version: 0.1.0
+package generatortest
+
+import (
+	"encoding/json"
+	"github.com/mitchellh/mapstructure"
+)
+
+// Baz is a oneOf type.
+type Baz struct {
+	data interface{}
+}
+
+// MarshalJSON implementes the json.Marshaller interface
+func (m *Baz) MarshalJSON() ([]byte, error) {
+	return json.Marshal(m.data)
+}
+
+// UnmarshalJSON implementes the json.Unmarshaller interface
+func (m *Baz) UnmarshalJSON(bs []byte) error {
+	return json.Unmarshal(bs, &m.data)
+}
+
+// As converts Baz to a user defined structure.
+func (m Baz) As(target interface{}) error {
+	return mapstructure.Decode(m.data, target)
+}
+
+// AsFoo converts Baz to a Foo
+func (m Baz) AsFoo() (result Foo, err error) {
+	return result, mapstructure.Decode(m.data, &result)
+}
+
+// AsBar converts Baz to a Bar
+func (m Baz) AsBar() (result Bar, err error) {
+	return result, mapstructure.Decode(m.data, &result)
+}
+
+// AsPerson converts Baz to a Person
+func (m Baz) AsPerson() (result Person, err error) {
+	return result, mapstructure.Decode(m.data, &result)
+}

pkg/generators/models/testdata/cases/oneof/expected/model_person.go

@@ -0,0 +1,43 @@
+// This file is auto-generated, DO NOT EDIT.
+//
+// Source:
+//     Title: Test
+//     Version: 0.1.0
+package generatortest
+
+import (
+	validation "github.com/go-ozzo/ozzo-validation/v4"
+)
+
+// Person is an object.
+type Person struct {
+	// Age:
+	Age int32 `json:"age,omitempty"`
+	// Name:
+	Name string `json:"name,omitempty"`
+}
+
+// Validate implements basic validation for this model
+func (m Person) Validate() error {
+	return validation.Errors{}.Filter()
+}
+
+// GetAge returns the Age property
+func (m Person) GetAge() int32 {
+	return m.Age
+}
+
+// SetAge sets the Age property
+func (m *Person) SetAge(val int32) {
+	m.Age = val
+}
+
+// GetName returns the Name property
+func (m Person) GetName() string {
+	return m.Name
+}
+
+// SetName sets the Name property
+func (m *Person) SetName(val string) {
+	m.Name = val
+}

pkg/generators/models/testdata/cases/oneof/generated/model_bar.go

@@ -5,5 +5,37 @@
 //     Version: 0.1.0
 package generatortest
 
-// Bar is a value type.
-type Bar interface{}
+import (
+	"encoding/json"
+	"github.com/mitchellh/mapstructure"
+)
+
+// Bar is a oneOf type.
+type Bar struct {
+	data interface{}
+}
+
+// MarshalJSON implementes the json.Marshaller interface
+func (m *Bar) MarshalJSON() ([]byte, error) {
+	return json.Marshal(m.data)
+}
+
+// UnmarshalJSON implementes the json.Unmarshaller interface
+func (m *Bar) UnmarshalJSON(bs []byte) error {
+	return json.Unmarshal(bs, &m.data)
+}
+
+// As converts Bar to a user defined structure.
+func (m Bar) As(target interface{}) error {
+	return mapstructure.Decode(m.data, target)
+}
+
+// AsString converts Bar to a string
+func (m Bar) AsString() (result string, err error) {
+	return result, mapstructure.Decode(m.data, &result)
+}
+
+// AsInt32 converts Bar to a int32
+func (m Bar) AsInt32() (result int32, err error) {
+	return result, mapstructure.Decode(m.data, &result)
+}

pkg/generators/models/testdata/cases/oneof/generated/model_baz.go

@@ -0,0 +1,46 @@
+// This file is auto-generated, DO NOT EDIT.
+//
+// Source:
+//     Title: Test
+//     Version: 0.1.0
+package generatortest
+
+import (
+	"encoding/json"
+	"github.com/mitchellh/mapstructure"
+)
+
+// Baz is a oneOf type.
+type Baz struct {
+	data interface{}
+}
+
+// MarshalJSON implementes the json.Marshaller interface
+func (m *Baz) MarshalJSON() ([]byte, error) {
+	return json.Marshal(m.data)
+}
+
+// UnmarshalJSON implementes the json.Unmarshaller interface
+func (m *Baz) UnmarshalJSON(bs []byte) error {
+	return json.Unmarshal(bs, &m.data)
+}
+
+// As converts Baz to a user defined structure.
+func (m Baz) As(target interface{}) error {
+	return mapstructure.Decode(m.data, target)
+}
+
+// AsFoo converts Baz to a Foo
+func (m Baz) AsFoo() (result Foo, err error) {
+	return result, mapstructure.Decode(m.data, &result)
+}
+
+// AsBar converts Baz to a Bar
+func (m Baz) AsBar() (result Bar, err error) {
+	return result, mapstructure.Decode(m.data, &result)
+}
+
+// AsPerson converts Baz to a Person
+func (m Baz) AsPerson() (result Person, err error) {
+	return result, mapstructure.Decode(m.data, &result)
+}