Copied mongo repo (to patch it)

mongo/bson/bsoncodec/empty_interface_codec.go

@@ -0,0 +1,147 @@
+// 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 bsoncodec
+
+import (
+	"reflect"
+
+	"go.mongodb.org/mongo-driver/bson/bsonoptions"
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+	"go.mongodb.org/mongo-driver/bson/primitive"
+)
+
+// EmptyInterfaceCodec is the Codec used for interface{} values.
+type EmptyInterfaceCodec struct {
+	DecodeBinaryAsSlice bool
+}
+
+var (
+	defaultEmptyInterfaceCodec = NewEmptyInterfaceCodec()
+
+	_ ValueCodec  = defaultEmptyInterfaceCodec
+	_ typeDecoder = defaultEmptyInterfaceCodec
+)
+
+// NewEmptyInterfaceCodec returns a EmptyInterfaceCodec with options opts.
+func NewEmptyInterfaceCodec(opts ...*bsonoptions.EmptyInterfaceCodecOptions) *EmptyInterfaceCodec {
+	interfaceOpt := bsonoptions.MergeEmptyInterfaceCodecOptions(opts...)
+
+	codec := EmptyInterfaceCodec{}
+	if interfaceOpt.DecodeBinaryAsSlice != nil {
+		codec.DecodeBinaryAsSlice = *interfaceOpt.DecodeBinaryAsSlice
+	}
+	return &codec
+}
+
+// EncodeValue is the ValueEncoderFunc for interface{}.
+func (eic EmptyInterfaceCodec) EncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tEmpty {
+		return ValueEncoderError{Name: "EmptyInterfaceEncodeValue", Types: []reflect.Type{tEmpty}, Received: val}
+	}
+
+	if val.IsNil() {
+		return vw.WriteNull()
+	}
+	encoder, err := ec.LookupEncoder(val.Elem().Type())
+	if err != nil {
+		return err
+	}
+
+	return encoder.EncodeValue(ec, vw, val.Elem())
+}
+
+func (eic EmptyInterfaceCodec) getEmptyInterfaceDecodeType(dc DecodeContext, valueType bsontype.Type) (reflect.Type, error) {
+	isDocument := valueType == bsontype.Type(0) || valueType == bsontype.EmbeddedDocument
+	if isDocument {
+		if dc.defaultDocumentType != nil {
+			// If the bsontype is an embedded document and the DocumentType is set on the DecodeContext, then return
+			// that type.
+			return dc.defaultDocumentType, nil
+		}
+		if dc.Ancestor != nil {
+			// Using ancestor information rather than looking up the type map entry forces consistent decoding.
+			// If we're decoding into a bson.D, subdocuments should also be decoded as bson.D, even if a type map entry
+			// has been registered.
+			return dc.Ancestor, nil
+		}
+	}
+
+	rtype, err := dc.LookupTypeMapEntry(valueType)
+	if err == nil {
+		return rtype, nil
+	}
+
+	if isDocument {
+		// For documents, fallback to looking up a type map entry for bsontype.Type(0) or bsontype.EmbeddedDocument,
+		// depending on the original valueType.
+		var lookupType bsontype.Type
+		switch valueType {
+		case bsontype.Type(0):
+			lookupType = bsontype.EmbeddedDocument
+		case bsontype.EmbeddedDocument:
+			lookupType = bsontype.Type(0)
+		}
+
+		rtype, err = dc.LookupTypeMapEntry(lookupType)
+		if err == nil {
+			return rtype, nil
+		}
+	}
+
+	return nil, err
+}
+
+func (eic EmptyInterfaceCodec) decodeType(dc DecodeContext, vr bsonrw.ValueReader, t reflect.Type) (reflect.Value, error) {
+	if t != tEmpty {
+		return emptyValue, ValueDecoderError{Name: "EmptyInterfaceDecodeValue", Types: []reflect.Type{tEmpty}, Received: reflect.Zero(t)}
+	}
+
+	rtype, err := eic.getEmptyInterfaceDecodeType(dc, vr.Type())
+	if err != nil {
+		switch vr.Type() {
+		case bsontype.Null:
+			return reflect.Zero(t), vr.ReadNull()
+		default:
+			return emptyValue, err
+		}
+	}
+
+	decoder, err := dc.LookupDecoder(rtype)
+	if err != nil {
+		return emptyValue, err
+	}
+
+	elem, err := decodeTypeOrValue(decoder, dc, vr, rtype)
+	if err != nil {
+		return emptyValue, err
+	}
+
+	if eic.DecodeBinaryAsSlice && rtype == tBinary {
+		binElem := elem.Interface().(primitive.Binary)
+		if binElem.Subtype == bsontype.BinaryGeneric || binElem.Subtype == bsontype.BinaryBinaryOld {
+			elem = reflect.ValueOf(binElem.Data)
+		}
+	}
+
+	return elem, nil
+}
+
+// DecodeValue is the ValueDecoderFunc for interface{}.
+func (eic EmptyInterfaceCodec) DecodeValue(dc DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
+	if !val.CanSet() || val.Type() != tEmpty {
+		return ValueDecoderError{Name: "EmptyInterfaceDecodeValue", Types: []reflect.Type{tEmpty}, Received: val}
+	}
+
+	elem, err := eic.decodeType(dc, vr, val.Type())
+	if err != nil {
+		return err
+	}
+
+	val.Set(elem)
+	return nil
+}