Add support for Undefined BSON type

wirebson/bson.go

@@ -26,6 +26,7 @@
 //	Double              float64
 //	String              string
 //	Binary data         Binary
+//	Undefined           UndefinedType
 //	ObjectId            ObjectID
 //	Boolean             bool
 //	Date                time.Time
@@ -64,7 +65,7 @@ type CompositeType interface {
 //
 // CString is not included as it is not a real BSON type.
 type ScalarType interface {
-	float64 | string | Binary | ObjectID | bool | time.Time | NullType | Regex | int32 | Timestamp | int64 | Decimal128
+	float64 | string | Binary | UndefinedType | ObjectID | bool | time.Time | NullType | Regex | int32 | Timestamp | int64 | Decimal128
 }
 
 // AnyDocument represents a BSON document type (both [*Document] and [RawDocument]).
@@ -97,6 +98,7 @@ func validBSONType(v any) error {
 	case float64:
 	case string:
 	case Binary:
+	case UndefinedType:
 	case ObjectID:
 	case bool:
 	case time.Time:
@@ -160,6 +162,8 @@ func fromDriver(v any) (any, error) {
 			Subtype: BinarySubtype(v.Subtype),
 			B:       v.Data,
 		}, nil
+	case bson.Undefined:
+		return Undefined, nil
 	case bson.ObjectID:
 		return ObjectID(v), nil
 	case bool:
@@ -234,14 +238,16 @@ func toDriver(v any) (any, error) {
 			Subtype: byte(v.Subtype),
 			Data:    v.B,
 		}, nil
+	case UndefinedType:
+		return bson.Undefined{}, nil
 	case ObjectID:
 		return bson.ObjectID(v), nil
 	case bool:
 		return v, nil
 	case time.Time:
 		return bson.NewDateTimeFromTime(v), nil
 	case NullType:
-		return nil, nil
+		return bson.Null{}, nil
 	case Regex:
 		return bson.Regex{
 			Pattern: v.Pattern,

wirebson/bson_test.go

@@ -283,6 +283,7 @@ var normalTestCases = []normalTestCase{
 				Binary{Subtype: BinaryUser, B: []byte{0x42}},
 				Binary{Subtype: BinaryGeneric, B: []byte{}},
 			),
+			"undefined", MustArray(Undefined),
 			"objectID", MustArray(ObjectID{0x42}, ObjectID{}),
 			"bool", MustArray(true, false),
 			"datetime", MustArray(
@@ -327,6 +328,9 @@ var normalTestCases = []normalTestCase{
 		    Binary(user:Qg==),
 		    Binary(generic:),
 		  ],
+		  "undefined": [
+		    undefined,
+		  ],
 		  "objectID": [
 		    ObjectID(420000000000000000000000),
 		    ObjectID(000000000000000000000000),
@@ -414,6 +418,11 @@ var normalTestCases = []normalTestCase{
 		      }
 		    }
 		  ],
+		  "undefined": [
+		    {
+		      "$undefined": true
+		    }
+		  ],
 		  "objectID": [
 		    {
 		      "$oid": "420000000000000000000000"
@@ -593,6 +602,21 @@ var normalTestCases = []normalTestCase{
 		  "f": Binary(user:dg==),
 		}`,
 	},
+	{
+		name: "undefinedDoc",
+		raw: RawDocument{
+			0x08, 0x00, 0x00, 0x00,
+			0x06, 0x66, 0x00,
+			0x00,
+		},
+		doc: MustDocument(
+			"f", Undefined,
+		),
+		mi: `
+		{
+		  "f": undefined,
+		}`,
+	},
 	{
 		name: "objectIDDoc",
 		raw: RawDocument{

wirebson/decode.go

@@ -105,7 +105,7 @@ func decodeScalarField(b []byte, t tag) (v any, size int, err error) {
 		size = sizeBinary(bin)
 
 	case tagUndefined:
-		err = lazyerrors.Errorf("unsupported tag %s: %w", t, ErrDecodeInvalidInput)
+		v = Undefined
 
 	case tagObjectID:
 		v, err = decodeObjectID(b)

wirebson/encode.go

@@ -119,6 +119,8 @@ func encodeScalarField(buf *bytes.Buffer, name string, v any) error {
 		buf.WriteByte(byte(tagString))
 	case Binary:
 		buf.WriteByte(byte(tagBinary))
+	case UndefinedType:
+		buf.WriteByte(byte(tagUndefined))
 	case ObjectID:
 		buf.WriteByte(byte(tagObjectID))
 	case bool:
@@ -172,6 +174,8 @@ func encodeScalarValue(b []byte, v any) {
 		encodeString(b, v)
 	case Binary:
 		encodeBinary(b, v)
+	case UndefinedType:
+		// nothing
 	case ObjectID:
 		encodeObjectID(b, v)
 	case bool:

wirebson/logging.go

@@ -110,6 +110,9 @@ func slogValue(v any, depth int) slog.Value {
 	case Binary:
 		return slog.StringValue(fmt.Sprintf("%#v", v))
 
+	case UndefinedType:
+		return slog.Value{}
+
 	case ObjectID:
 		return slog.StringValue("ObjectID(" + hex.EncodeToString(v[:]) + ")")
 
@@ -301,6 +304,9 @@ func logMessage(v any, indent, depth int, b *strings.Builder) {
 		b.WriteString(base64.StdEncoding.EncodeToString(v.B))
 		b.WriteByte(')')
 
+	case UndefinedType:
+		b.WriteString("undefined")
+
 	case ObjectID:
 		b.WriteString("ObjectID(")
 		b.WriteString(hex.EncodeToString(v[:]))

wirebson/size.go

@@ -71,6 +71,8 @@ func sizeScalar(v any) int {
 		return sizeString(v)
 	case Binary:
 		return sizeBinary(v)
+	case UndefinedType:
+		return 0
 	case ObjectID:
 		return sizeObjectID
 	case bool:

wirebson/testdata/all.hex

@@ -1,4 +1,4 @@
-00000000  13 02 00 00 04 64 6f 63  75 6d 65 6e 74 00 36 00  |.....document.6.|
+00000000  26 02 00 00 04 64 6f 63  75 6d 65 6e 74 00 36 00  |&....document.6.|
 00000010  00 00 03 30 00 26 00 00  00 02 00 04 00 00 00 66  |...0.&.........f|
 00000020  6f 6f 00 02 62 61 72 00  04 00 00 00 62 61 7a 00  |oo..bar.....baz.|
 00000030  02 00 04 00 00 00 71 75  78 00 00 03 31 00 05 00  |......qux...1...|
@@ -12,23 +12,24 @@
 000000b0  04 73 74 72 69 6e 67 00  18 00 00 00 02 30 00 04  |.string......0..|
 000000c0  00 00 00 66 6f 6f 00 02  31 00 01 00 00 00 00 00  |...foo..1.......|
 000000d0  04 62 69 6e 61 72 79 00  16 00 00 00 05 30 00 01  |.binary......0..|
-000000e0  00 00 00 80 42 05 31 00  00 00 00 00 00 00 04 6f  |....B.1........o|
-000000f0  62 6a 65 63 74 49 44 00  23 00 00 00 07 30 00 42  |bjectID.#....0.B|
-00000100  00 00 00 00 00 00 00 00  00 00 00 07 31 00 00 00  |............1...|
-00000110  00 00 00 00 00 00 00 00  00 00 00 04 62 6f 6f 6c  |............bool|
-00000120  00 0d 00 00 00 08 30 00  01 08 31 00 00 00 04 64  |......0...1....d|
-00000130  61 74 65 74 69 6d 65 00  1b 00 00 00 09 30 00 2b  |atetime......0.+|
-00000140  e6 51 e7 7a 01 00 00 09  31 00 00 28 d3 ed 7c c7  |.Q.z....1..(..|.|
-00000150  ff ff 00 04 6e 75 6c 6c  00 08 00 00 00 0a 30 00  |....null......0.|
-00000160  00 04 72 65 67 65 78 00  11 00 00 00 0b 30 00 70  |..regex......0.p|
-00000170  00 6f 00 0b 31 00 00 00  00 04 69 6e 74 33 32 00  |.o..1.....int32.|
-00000180  13 00 00 00 10 30 00 2a  00 00 00 10 31 00 00 00  |.....0.*....1...|
-00000190  00 00 00 04 74 69 6d 65  73 74 61 6d 70 00 1b 00  |....timestamp...|
-000001a0  00 00 11 30 00 2a 00 00  00 00 00 00 00 11 31 00  |...0.*........1.|
-000001b0  00 00 00 00 00 00 00 00  00 04 69 6e 74 36 34 00  |..........int64.|
-000001c0  1b 00 00 00 12 30 00 2a  00 00 00 00 00 00 00 12  |.....0.*........|
-000001d0  31 00 00 00 00 00 00 00  00 00 00 04 64 65 63 69  |1...........deci|
-000001e0  6d 61 6c 31 32 38 00 2b  00 00 00 13 30 00 2a 00  |mal128.+....0.*.|
-000001f0  00 00 00 00 00 00 0d 00  00 00 00 00 00 00 13 31  |...............1|
-00000200  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
-00000210  00 00 00                                          |...|
+000000e0  00 00 00 80 42 05 31 00  00 00 00 00 00 00 04 75  |....B.1........u|
+000000f0  6e 64 65 66 69 6e 65 64  00 08 00 00 00 06 30 00  |ndefined......0.|
+00000100  00 04 6f 62 6a 65 63 74  49 44 00 23 00 00 00 07  |..objectID.#....|
+00000110  30 00 42 00 00 00 00 00  00 00 00 00 00 00 07 31  |0.B............1|
+00000120  00 00 00 00 00 00 00 00  00 00 00 00 00 00 04 62  |...............b|
+00000130  6f 6f 6c 00 0d 00 00 00  08 30 00 01 08 31 00 00  |ool......0...1..|
+00000140  00 04 64 61 74 65 74 69  6d 65 00 1b 00 00 00 09  |..datetime......|
+00000150  30 00 2b e6 51 e7 7a 01  00 00 09 31 00 00 28 d3  |0.+.Q.z....1..(.|
+00000160  ed 7c c7 ff ff 00 04 6e  75 6c 6c 00 08 00 00 00  |.|.....null.....|
+00000170  0a 30 00 00 04 72 65 67  65 78 00 11 00 00 00 0b  |.0...regex......|
+00000180  30 00 70 00 6f 00 0b 31  00 00 00 00 04 69 6e 74  |0.p.o..1.....int|
+00000190  33 32 00 13 00 00 00 10  30 00 2a 00 00 00 10 31  |32......0.*....1|
+000001a0  00 00 00 00 00 00 04 74  69 6d 65 73 74 61 6d 70  |.......timestamp|
+000001b0  00 1b 00 00 00 11 30 00  2a 00 00 00 00 00 00 00  |......0.*.......|
+000001c0  11 31 00 00 00 00 00 00  00 00 00 00 04 69 6e 74  |.1...........int|
+000001d0  36 34 00 1b 00 00 00 12  30 00 2a 00 00 00 00 00  |64......0.*.....|
+000001e0  00 00 12 31 00 00 00 00  00 00 00 00 00 00 04 64  |...1...........d|
+000001f0  65 63 69 6d 61 6c 31 32  38 00 2b 00 00 00 13 30  |ecimal128.+....0|
+00000200  00 2a 00 00 00 00 00 00  00 0d 00 00 00 00 00 00  |.*..............|
+00000210  00 13 31 00 00 00 00 00  00 00 00 00 00 00 00 00  |..1.............|
+00000220  00 00 00 00 00 00                                 |......|

wirebson/undefined.go

@@ -0,0 +1,24 @@
+// Copyright 2021 FerretDB Inc.
+//
+// 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
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package wirebson
+
+// UndefinedType represents BSON scalar type undefined.
+type UndefinedType struct{}
+
+// Undefined represents BSON scalar value undefined.
+//
+// Its usage is deprecated, but it is still used in a few places.
+// See https://github.com/FerretDB/FerretDB/issues/2286 for an example.
+var Undefined = UndefinedType{}

wirebson/undefined_test.go

@@ -0,0 +1,35 @@
+// Copyright 2021 FerretDB Inc.
+//
+// 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
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package wirebson
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestUndefinedNull(t *testing.T) {
+	assert.Equal(t, Undefined, Undefined)
+	assert.Equal(t, Null, Null)
+
+	assert.NotEqual(t, Undefined, Null)
+	assert.EqualValues(t, Undefined, Null)
+
+	assert.Equal(t, UndefinedType{}, Undefined)
+	assert.Equal(t, NullType{}, Null)
+
+	assert.NotEqual(t, UndefinedType{}, Null)
+	assert.EqualValues(t, UndefinedType{}, Null)
+}