WIP

go.mod

@@ -1,3 +1,5 @@
 module github.com/oapi-codegen/nullable
 
 go 1.20
+
+require gopkg.in/yaml.v3 v3.0.1

internal/test/go.mod

@@ -7,10 +7,10 @@ replace github.com/oapi-codegen/nullable => ../../
 require (
 	github.com/oapi-codegen/nullable v0.0.0-00010101000000-000000000000
 	github.com/stretchr/testify v1.8.4
+	gopkg.in/yaml.v3 v3.0.1
 )
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

internal/test/nullable_test.go

@@ -5,12 +5,13 @@ import (
 	"testing"
 
 	"github.com/oapi-codegen/nullable"
+	"gopkg.in/yaml.v3"
 
 	"github.com/stretchr/testify/require"
 )
 
 type Obj struct {
-	Foo nullable.Nullable[string] `json:"foo,omitempty"` // note "omitempty" is important for fields that are optional
+	Foo nullable.Nullable[string] `json:"foo,omitempty",yaml:"foo,omitempty"` // note "omitempty" is important for fields that are optional
 }
 
 func TestNullable(t *testing.T) {
@@ -88,3 +89,79 @@ func serialize(o Obj, t *testing.T) string {
 	require.NoError(t, err)
 	return string(data)
 }
+
+func TestNullableYAML(t *testing.T) {
+	// --- parsing from json and serializing back to JSON
+
+	// -- case where there is an actual value
+	data := `foo: bar`
+	// deserialize from json
+	myObj := parseYAML(data, t)
+	require.Equal(t, myObj, Obj{Foo: nullable.Nullable[string]{true: "bar"}})
+	require.False(t, myObj.Foo.IsNull())
+	require.True(t, myObj.Foo.IsSpecified())
+	value, err := myObj.Foo.Get()
+	require.NoError(t, err)
+	require.Equal(t, "bar", value)
+	require.Equal(t, "bar", myObj.Foo.MustGet())
+	// serialize back to json: leads to the same data
+	require.Equal(t, data, serializeYAML(myObj, t))
+
+	// -- case where no value is specified: parsed from JSON
+	data = ``
+	// deserialize from json
+	myObj = parseYAML(data, t)
+	require.Equal(t, myObj, Obj{Foo: nil})
+	require.False(t, myObj.Foo.IsNull())
+	require.False(t, myObj.Foo.IsSpecified())
+	_, err = myObj.Foo.Get()
+	require.ErrorContains(t, err, "value is not specified")
+	// serialize back to json: leads to the same data
+	require.Equal(t, data, serializeYAML(myObj, t))
+
+	// -- case where the specified value is explicitly null
+	data = `foo:null`
+	// deserialize from json
+	myObj = parseYAML(data, t)
+	require.Equal(t, myObj, Obj{Foo: nullable.Nullable[string]{false: ""}})
+	require.True(t, myObj.Foo.IsNull())
+	require.True(t, myObj.Foo.IsSpecified())
+	_, err = myObj.Foo.Get()
+	require.ErrorContains(t, err, "value is null")
+	require.Panics(t, func() { myObj.Foo.MustGet() })
+	// serialize back to json: leads to the same data
+	require.Equal(t, data, serializeYAML(myObj, t))
+
+	// --- building objects from a Go client
+
+	// - case where there is an actual value
+	myObj = Obj{}
+	myObj.Foo.Set("bar")
+	require.Equal(t, `foo:"bar"`, serialize(myObj, t))
+
+	// - case where the value should be unspecified
+	myObj = Obj{}
+	// do nothing: unspecified by default
+	require.Equal(t, ``, serializeYAML(myObj, t))
+	// explicitly mark unspecified
+	myObj.Foo.SetUnspecified()
+	require.Equal(t, ``, serializeYAML(myObj, t))
+
+	// - case where the value should be null
+	myObj = Obj{}
+	myObj.Foo.SetNull()
+	require.Equal(t, `foo:null`, serialize(myObj, t))
+}
+
+func parseYAML(data string, t *testing.T) Obj {
+	var myObj Obj
+	err := yaml.Unmarshal([]byte(data), &myObj)
+	require.NoError(t, err)
+	return myObj
+}
+
+func serializeYAML(o Obj, t *testing.T) string {
+	data, err := yaml.Marshal(o)
+	require.NoError(t, err)
+	return string(data)
+}

nullable.go

@@ -4,6 +4,10 @@ import (
 	"bytes"
 	"encoding/json"
 	"errors"
+	"fmt"
+	"reflect"
+
+	"gopkg.in/yaml.v3"
 )
 
 // Nullable is a generic type, which implements a field that can be one of three states:
@@ -115,3 +119,49 @@ func (t *Nullable[T]) UnmarshalJSON(data []byte) error {
 	t.Set(v)
 	return nil
 }
+
+// TODO pointer receiver https://github.com/go-yaml/yaml/issues/134#issuecomment-2044424851
+func (t Nullable[T]) MarshalYAML() (interface{}, error) {
+	fmt.Println("MarshalYAML")
+	// if field was specified, and `null`, marshal it
+	if t.IsNull() {
+		return []byte("null"), nil
+	}
+
+	// if field was unspecified, and `omitempty` is set on the field's tags, `json.Marshal` will omit this field
+
+	// otherwise: we have a value, so marshal it
+	// fmt.Printf("t[true]: %v\n", t[true])
+	// b, _ := yaml.Marshal(t[true])
+	// fmt.Printf("b: %v\n", b)
+	// return yaml.Marshal(t[true])
+	vv := (t)[true]
+	fmt.Printf("vv: %v\n", vv)
+	fmt.Printf("reflect.ValueOf(vv): %v\n", reflect.ValueOf(vv))
+	return json.Marshal(t[true])
+}
+
+func (t *Nullable[T]) UnmarshalYAML(value *yaml.Node) error {
+	// if field is unspecified, UnmarshalJSON won't be called
+	// fmt.Printf("value: %v\n", value)
+	// value.Kind == yaml.Kind
+
+	fmt.Printf("value: %v\n", value)
+	fmt.Printf("value.Tag: %v\n", value.Tag)
+
+	//////	// if field is specified, and `null`
+	//////	if bytes.Equal(data, []byte("null")) {
+	//////		t.SetNull()
+	//////		return nil
+	//////	}
+	// otherwise, we have an actual value, so parse it
+	var v T
+
+	fmt.Printf("reflect.TypeOf(v): %v\n", reflect.TypeOf(v))
+	if err := value.Decode(&v); err != nil {
+		return err
+	}
+	fmt.Printf("v: %v\n", v)
+	t.Set(v)
+	return nil
+}