Copied mongo repo (to patch it)

mongo/bson/mgocompat/setter_getter.go

@@ -0,0 +1,127 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package mgocompat
+
+import (
+	"reflect"
+
+	"go.mongodb.org/mongo-driver/bson"
+	"go.mongodb.org/mongo-driver/bson/bsoncodec"
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+)
+
+// Setter interface: a value implementing the bson.Setter interface will receive the BSON
+// value via the SetBSON method during unmarshaling, and the object
+// itself will not be changed as usual.
+//
+// If setting the value works, the method should return nil or alternatively
+// mgocompat.ErrSetZero to set the respective field to its zero value (nil for
+// pointer types). If SetBSON returns a non-nil error, the unmarshalling
+// procedure will stop and error out with the provided value.
+//
+// This interface is generally useful in pointer receivers, since the method
+// will want to change the receiver. A type field that implements the Setter
+// interface doesn't have to be a pointer, though.
+//
+// For example:
+//
+//	type MyString string
+//
+//	func (s *MyString) SetBSON(raw bson.RawValue) error {
+//	    return raw.Unmarshal(s)
+//	}
+type Setter interface {
+	SetBSON(raw bson.RawValue) error
+}
+
+// Getter interface: a value implementing the bson.Getter interface will have its GetBSON
+// method called when the given value has to be marshalled, and the result
+// of this method will be marshaled in place of the actual object.
+//
+// If GetBSON returns return a non-nil error, the marshalling procedure
+// will stop and error out with the provided value.
+type Getter interface {
+	GetBSON() (interface{}, error)
+}
+
+// SetterDecodeValue is the ValueDecoderFunc for Setter types.
+func SetterDecodeValue(dc bsoncodec.DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
+	if !val.IsValid() || (!val.Type().Implements(tSetter) && !reflect.PtrTo(val.Type()).Implements(tSetter)) {
+		return bsoncodec.ValueDecoderError{Name: "SetterDecodeValue", Types: []reflect.Type{tSetter}, Received: val}
+	}
+
+	if val.Kind() == reflect.Ptr && val.IsNil() {
+		if !val.CanSet() {
+			return bsoncodec.ValueDecoderError{Name: "SetterDecodeValue", Types: []reflect.Type{tSetter}, Received: val}
+		}
+		val.Set(reflect.New(val.Type().Elem()))
+	}
+
+	if !val.Type().Implements(tSetter) {
+		if !val.CanAddr() {
+			return bsoncodec.ValueDecoderError{Name: "ValueUnmarshalerDecodeValue", Types: []reflect.Type{tSetter}, Received: val}
+		}
+		val = val.Addr() // If the type doesn't implement the interface, a pointer to it must.
+	}
+
+	t, src, err := bsonrw.Copier{}.CopyValueToBytes(vr)
+	if err != nil {
+		return err
+	}
+
+	fn := val.Convert(tSetter).MethodByName("SetBSON")
+
+	errVal := fn.Call([]reflect.Value{reflect.ValueOf(bson.RawValue{Type: t, Value: src})})[0]
+	if !errVal.IsNil() {
+		err = errVal.Interface().(error)
+		if err == ErrSetZero {
+			val.Set(reflect.Zero(val.Type()))
+			return nil
+		}
+		return err
+	}
+	return nil
+}
+
+// GetterEncodeValue is the ValueEncoderFunc for Getter types.
+func GetterEncodeValue(ec bsoncodec.EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	// Either val or a pointer to val must implement Getter
+	switch {
+	case !val.IsValid():
+		return bsoncodec.ValueEncoderError{Name: "GetterEncodeValue", Types: []reflect.Type{tGetter}, Received: val}
+	case val.Type().Implements(tGetter):
+		// If Getter is implemented on a concrete type, make sure that val isn't a nil pointer
+		if isImplementationNil(val, tGetter) {
+			return vw.WriteNull()
+		}
+	case reflect.PtrTo(val.Type()).Implements(tGetter) && val.CanAddr():
+		val = val.Addr()
+	default:
+		return bsoncodec.ValueEncoderError{Name: "GetterEncodeValue", Types: []reflect.Type{tGetter}, Received: val}
+	}
+
+	fn := val.Convert(tGetter).MethodByName("GetBSON")
+	returns := fn.Call(nil)
+	if !returns[1].IsNil() {
+		return returns[1].Interface().(error)
+	}
+	intermediate := returns[0]
+	encoder, err := ec.Registry.LookupEncoder(intermediate.Type())
+	if err != nil {
+		return err
+	}
+	return encoder.EncodeValue(ec, vw, intermediate)
+}
+
+// isImplementationNil returns if val is a nil pointer and inter is implemented on a concrete type
+func isImplementationNil(val reflect.Value, inter reflect.Type) bool {
+	vt := val.Type()
+	for vt.Kind() == reflect.Ptr {
+		vt = vt.Elem()
+	}
+	return vt.Implements(inter) && val.Kind() == reflect.Ptr && val.IsNil()
+}