chore: implement encoding.Unmarshal (#975)

fixes #971
fixes #951

backend/controller/ingress/request_test.go

@@ -2,7 +2,6 @@ package ingress
 
 import (
 	"bytes"
-	"encoding/json"
 	"net/http"
 	"net/url"
 	"reflect"
@@ -17,8 +16,7 @@ import (
 )
 
 type AliasRequest struct {
-	// FIXME: This should be an alias (`json:"alias"`) once encoding.Unmarshal is available.
-	Aliased string
+	Aliased string `json:"alias"`
 }
 
 type PathParameterRequest struct {
@@ -184,7 +182,7 @@ func TestBuildRequestBody(t *testing.T) {
 			assert.NoError(t, err)
 			actualrv := reflect.New(reflect.TypeOf(test.expected))
 			actual := actualrv.Interface()
-			err = json.Unmarshal(requestBody, actual)
+			err = encoding.Unmarshal(requestBody, actual)
 			assert.NoError(t, err)
 			assert.Equal(t, test.expected, actualrv.Elem().Interface(), assert.OmitEmpty())
 		})

go-runtime/encoding/encoding.go

@@ -15,8 +15,10 @@ import (
 )
 
 var (
-	textUnarmshaler = reflect.TypeOf((*encoding.TextMarshaler)(nil)).Elem()
-	jsonUnmarshaler = reflect.TypeOf((*json.Marshaler)(nil)).Elem()
+	textMarshaler   = reflect.TypeOf((*encoding.TextMarshaler)(nil)).Elem()
+	textUnmarshaler = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
+	jsonMarshaler   = reflect.TypeOf((*json.Marshaler)(nil)).Elem()
+	jsonUnmarshaler = reflect.TypeOf((*json.Unmarshaler)(nil)).Elem()
 )
 
 func Marshal(v any) ([]byte, error) {
@@ -32,11 +34,11 @@ func encodeValue(v reflect.Value, w *bytes.Buffer) error {
 	}
 	t := v.Type()
 	switch {
-	case t.Kind() == reflect.Ptr && t.Elem().Implements(jsonUnmarshaler):
+	case t.Kind() == reflect.Ptr && t.Elem().Implements(jsonMarshaler):
 		v = v.Elem()
 		fallthrough
 
-	case t.Implements(jsonUnmarshaler):
+	case t.Implements(jsonMarshaler):
 		enc := v.Interface().(json.Marshaler) //nolint:forcetypeassert
 		data, err := enc.MarshalJSON()
 		if err != nil {
@@ -45,11 +47,11 @@ func encodeValue(v reflect.Value, w *bytes.Buffer) error {
 		w.Write(data)
 		return nil
 
-	case t.Kind() == reflect.Ptr && t.Elem().Implements(textUnarmshaler):
+	case t.Kind() == reflect.Ptr && t.Elem().Implements(textMarshaler):
 		v = v.Elem()
 		fallthrough
 
-	case t.Implements(textUnarmshaler):
+	case t.Implements(textMarshaler):
 		enc := v.Interface().(encoding.TextMarshaler) //nolint:forcetypeassert
 		data, err := enc.MarshalText()
 		if err != nil {
@@ -198,3 +200,185 @@ func encodeString(v reflect.Value, w *bytes.Buffer) error {
 	w.WriteRune('"')
 	return nil
 }
+
+func Unmarshal(data []byte, v any) error {
+	rv := reflect.ValueOf(v)
+	if rv.Kind() != reflect.Ptr || rv.IsNil() {
+		return fmt.Errorf("unmarshal expects a non-nil pointer")
+	}
+
+	d := json.NewDecoder(bytes.NewReader(data))
+	return decodeValue(d, rv.Elem())
+}
+
+func decodeValue(d *json.Decoder, v reflect.Value) error {
+	if !v.CanSet() {
+		return fmt.Errorf("cannot set value")
+	}
+
+	t := v.Type()
+	switch {
+	case v.Kind() != reflect.Ptr && v.CanAddr() && v.Addr().Type().Implements(jsonUnmarshaler):
+		v = v.Addr()
+		fallthrough
+
+	case t.Implements(jsonUnmarshaler):
+		if v.IsNil() {
+			v.Set(reflect.New(t.Elem()))
+		}
+		o := v.Interface()
+		return d.Decode(&o)
+
+	case v.Kind() != reflect.Ptr && v.CanAddr() && v.Addr().Type().Implements(textUnmarshaler):
+		v = v.Addr()
+		fallthrough
+
+	case t.Implements(textUnmarshaler):
+		if v.IsNil() {
+			v.Set(reflect.New(t.Elem()))
+		}
+		dec := v.Interface().(encoding.TextUnmarshaler) //nolint:forcetypeassert
+		var s string
+		if err := d.Decode(&s); err != nil {
+			return err
+		}
+		return dec.UnmarshalText([]byte(s))
+	}
+
+	switch v.Kind() {
+	case reflect.Struct:
+		return decodeStruct(d, v)
+
+	case reflect.Ptr:
+		if token, err := d.Token(); err != nil {
+			return err
+		} else if token == nil {
+			v.Set(reflect.Zero(v.Type()))
+			return nil
+		}
+		return decodeValue(d, v.Elem())
+
+	case reflect.Slice:
+		if v.Type().Elem().Kind() == reflect.Uint8 {
+			return decodeBytes(d, v)
+		}
+		return decodeSlice(d, v)
+
+	case reflect.Map:
+		return decodeMap(d, v)
+
+	case reflect.Interface:
+		if v.Type().NumMethod() != 0 {
+			return fmt.Errorf("the only interface type supported is any, not %s", v.Type())
+		}
+		fallthrough
+
+	default:
+		return d.Decode(v.Addr().Interface())
+	}
+}
+
+func decodeStruct(d *json.Decoder, v reflect.Value) error {
+	if err := expectDelim(d, '{'); err != nil {
+		return err
+	}
+
+	for d.More() {
+		token, err := d.Token()
+		if err != nil {
+			return err
+		}
+		key, ok := token.(string)
+		if !ok {
+			return fmt.Errorf("expected string key, got %T", token)
+		}
+
+		field := v.FieldByNameFunc(func(s string) bool {
+			return strcase.ToLowerCamel(s) == key
+		})
+		if !field.IsValid() {
+			return fmt.Errorf("no field corresponding to key %s", key)
+		}
+		fieldTypeStr := field.Type().String()
+		switch {
+		case fieldTypeStr == "*Unit" || fieldTypeStr == "Unit":
+			if fieldTypeStr == "*Unit" && field.IsNil() {
+				field.Set(reflect.New(field.Type().Elem()))
+			}
+		default:
+			if err := decodeValue(d, field); err != nil {
+				return err
+			}
+		}
+	}
+
+	// consume the closing delimiter of the object
+	_, err := d.Token()
+	return err
+}
+
+func decodeBytes(d *json.Decoder, v reflect.Value) error {
+	var b []byte
+	if err := d.Decode(&b); err != nil {
+		return err
+	}
+	v.SetBytes(b)
+	return nil
+}
+
+func decodeSlice(d *json.Decoder, v reflect.Value) error {
+	if err := expectDelim(d, '['); err != nil {
+		return err
+	}
+
+	for d.More() {
+		newElem := reflect.New(v.Type().Elem()).Elem()
+		if err := decodeValue(d, newElem); err != nil {
+			return err
+		}
+		v.Set(reflect.Append(v, newElem))
+	}
+	// consume the closing delimiter of the slice
+	_, err := d.Token()
+	return err
+}
+
+func decodeMap(d *json.Decoder, v reflect.Value) error {
+	if err := expectDelim(d, '{'); err != nil {
+		return err
+	}
+
+	if v.IsNil() {
+		v.Set(reflect.MakeMap(v.Type()))
+	}
+
+	valType := v.Type().Elem()
+	for d.More() {
+		key, err := d.Token()
+		if err != nil {
+			return err
+		}
+
+		newElem := reflect.New(valType).Elem()
+		if err := decodeValue(d, newElem); err != nil {
+			return err
+		}
+
+		v.SetMapIndex(reflect.ValueOf(key), newElem)
+	}
+	// consume the closing delimiter of the map
+	_, err := d.Token()
+	return err
+}
+
+func expectDelim(d *json.Decoder, expected json.Delim) error {
+	token, err := d.Token()
+	if err != nil {
+		return err
+	}
+	delim, ok := token.(json.Delim)
+	if !ok || delim != expected {
+		return fmt.Errorf("expected delimiter %q, got %q", expected, token)
+	}
+	return nil
+}

go-runtime/encoding/encoding_test.go

@@ -1,6 +1,7 @@
 package encoding_test
 
 import (
+	"reflect"
 	"testing"
 
 	. "github.com/TBD54566975/ftl/go-runtime/encoding"
@@ -31,6 +32,11 @@ func TestMarshal(t *testing.T) {
 		{name: "Option", input: struct{ Option ftl.Option[int] }{ftl.Some(42)}, expected: `{"option":42}`},
 		{name: "OptionPtr", input: struct{ Option *ftl.Option[int] }{&somePtr}, expected: `{"option":42}`},
 		{name: "OptionStruct", input: struct{ Option ftl.Option[inner] }{ftl.Some(inner{"foo"})}, expected: `{"option":{"fooBar":"foo"}}`},
+		{name: "Unit", input: ftl.Unit{}, expected: `{}`},
+		{name: "UnitField", input: struct {
+			String string
+			Unit   ftl.Unit
+		}{String: "something", Unit: ftl.Unit{}}, expected: `{"string":"something"}`},
 	}
 
 	for _, tt := range tests {
@@ -41,3 +47,96 @@ func TestMarshal(t *testing.T) {
 		})
 	}
 }
+
+func TestUnmarshal(t *testing.T) {
+	type inner struct {
+		FooBar string
+	}
+	somePtr := ftl.Some(42)
+	tests := []struct {
+		name     string
+		input    string
+		expected any
+		err      string
+	}{
+		{name: "FieldRenaming", input: `{"fooBar":""}`, expected: struct{ FooBar string }{""}},
+		{name: "String", input: `{"string":"foo"}`, expected: struct{ String string }{"foo"}},
+		{name: "Int", input: `{"int":42}`, expected: struct{ Int int }{42}},
+		{name: "Float", input: `{"float":42.42}`, expected: struct{ Float float64 }{42.42}},
+		{name: "Bool", input: `{"bool":true}`, expected: struct{ Bool bool }{true}},
+		{name: "Nil", input: `{"nil":null}`, expected: struct{ Nil *int }{nil}},
+		{name: "Slice", input: `{"slice":[1,2,3]}`, expected: struct{ Slice []int }{[]int{1, 2, 3}}},
+		{name: "SliceOfStrings", input: `{"slice":["hello","world"]}`, expected: struct{ Slice []string }{[]string{"hello", "world"}}},
+		{name: "Map", input: `{"map":{"foo":42}}`, expected: struct{ Map map[string]int }{map[string]int{"foo": 42}}},
+		{name: "Option", input: `{"option":42}`, expected: struct{ Option ftl.Option[int] }{ftl.Some(42)}},
+		{name: "OptionPtr", input: `{"option":42}`, expected: struct{ Option *ftl.Option[int] }{&somePtr}},
+		{name: "OptionStruct", input: `{"option":{"fooBar":"foo"}}`, expected: struct{ Option ftl.Option[inner] }{ftl.Some(inner{"foo"})}},
+		{name: "Unit", input: `{}`, expected: ftl.Unit{}},
+		{name: "UnitField", input: `{"string":"something"}`, expected: struct {
+			String string
+			Unit   ftl.Unit
+		}{String: "something", Unit: ftl.Unit{}}},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			eType := reflect.TypeOf(tt.expected)
+			if eType.Kind() == reflect.Ptr {
+				eType = eType.Elem()
+			}
+			o := reflect.New(eType)
+			err := Unmarshal([]byte(tt.input), o.Interface())
+			assert.EqualError(t, err, tt.err)
+			assert.Equal(t, tt.expected, o.Elem().Interface())
+		})
+	}
+}
+
+func TestRoundTrip(t *testing.T) {
+	type inner struct {
+		FooBar string
+	}
+	somePtr := ftl.Some(42)
+	tests := []struct {
+		name  string
+		input any
+	}{
+		{name: "FieldRenaming", input: struct{ FooBar string }{""}},
+		{name: "String", input: struct{ String string }{"foo"}},
+		{name: "Int", input: struct{ Int int }{42}},
+		{name: "Float", input: struct{ Float float64 }{42.42}},
+		{name: "Bool", input: struct{ Bool bool }{true}},
+		{name: "Nil", input: struct{ Nil *int }{nil}},
+		{name: "Slice", input: struct{ Slice []int }{[]int{1, 2, 3}}},
+		{name: "SliceOfStrings", input: struct{ Slice []string }{[]string{"hello", "world"}}},
+		{name: "Map", input: struct{ Map map[string]int }{map[string]int{"foo": 42}}},
+		{name: "Option", input: struct{ Option ftl.Option[int] }{ftl.Some(42)}},
+		{name: "OptionPtr", input: struct{ Option *ftl.Option[int] }{&somePtr}},
+		{name: "OptionStruct", input: struct{ Option ftl.Option[inner] }{ftl.Some(inner{"foo"})}},
+		{name: "Unit", input: ftl.Unit{}},
+		{name: "UnitField", input: struct {
+			String string
+			Unit   ftl.Unit
+		}{String: "something", Unit: ftl.Unit{}}},
+		{name: "Aliased", input: struct {
+			TokenID string `json:"token_id"`
+		}{"123"}},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			marshaled, err := Marshal(tt.input)
+			assert.NoError(t, err)
+
+			eType := reflect.TypeOf(tt.input)
+			if eType.Kind() == reflect.Ptr {
+				eType = eType.Elem()
+			}
+			o := reflect.New(eType)
+			err = Unmarshal(marshaled, o.Interface())
+			assert.NoError(t, err)
+
+			assert.Equal(t, tt.input, o.Elem().Interface())
+		})
+	}
+}

go-runtime/ftl/call.go

@@ -2,7 +2,6 @@ package ftl
 
 import (
 	"context"
-	"encoding/json"
 	"fmt"
 	"reflect"
 	"runtime"
@@ -34,7 +33,7 @@ func Call[Req, Resp any](ctx context.Context, verb Verb[Req, Resp], req Req) (re
 		return resp, fmt.Errorf("%s: %s", callee, cresp.Error.Message)
 
 	case *ftlv1.CallResponse_Body:
-		err = json.Unmarshal(cresp.Body, &resp)
+		err = encoding.Unmarshal(cresp.Body, &resp)
 		if err != nil {
 			return resp, fmt.Errorf("%s: failed to decode response: %w", callee, err)
 		}

go-runtime/ftl/option.go

@@ -179,7 +179,7 @@ func (o *Option[T]) UnmarshalJSON(data []byte) error {
 		o.ok = false
 		return nil
 	}
-	if err := json.Unmarshal(data, &o.value); err != nil {
+	if err := ftlencoding.Unmarshal(data, &o.value); err != nil {
 		return err
 	}
 	o.ok = true