Array and Composite codecs handle typed nils

fixes: #2453

Author: jackc

pgtype/array_codec.go

@@ -131,7 +131,7 @@ func (p *encodePlanArrayCodecText) Encode(value any, buf []byte) (newBuf []byte,
 
 		elem := array.Index(i)
 		var elemBuf []byte
-		if elem != nil {
+		if isNil, _ := isNilDriverValuer(elem); !isNil {
 			elemType := reflect.TypeOf(elem)
 			if lastElemType != elemType {
 				lastElemType = elemType
@@ -195,7 +195,7 @@ func (p *encodePlanArrayCodecBinary) Encode(value any, buf []byte) (newBuf []byt
 
 		elem := array.Index(i)
 		var elemBuf []byte
-		if elem != nil {
+		if isNil, _ := isNilDriverValuer(elem); !isNil {
 			elemType := reflect.TypeOf(elem)
 			if lastElemType != elemType {
 				lastElemType = elemType

pgtype/array_codec_test.go

@@ -116,6 +116,21 @@ func TestArrayCodecArray(t *testing.T) {
 	})
 }
 
+func TestArrayCodecPointerToNil(t *testing.T) {
+	pgxtest.RunWithQueryExecModes(context.Background(), t, defaultConnTestRunner, nil, func(ctx context.Context, t testing.TB, conn *pgx.Conn) {
+		n := int32(42)
+		input := []*int32{&n, nil}
+		var actual []*int32
+		err := conn.QueryRow(
+			ctx,
+			"select $1::int[]",
+			input,
+		).Scan(&actual)
+		require.NoError(t, err)
+		require.Equal(t, input, actual)
+	})
+}
+
 func TestArrayCodecNamedSliceType(t *testing.T) {
 	defaultConnTestRunner.RunTest(context.Background(), t, func(ctx context.Context, t testing.TB, conn *pgx.Conn) {
 		type _int16Slice []int16

pgtype/composite.go

@@ -476,7 +476,7 @@ func (b *CompositeBinaryBuilder) AppendValue(oid uint32, field any) {
 		return
 	}
 
-	if field == nil {
+	if isNil, _ := isNilDriverValuer(field); isNil {
 		b.buf = pgio.AppendUint32(b.buf, oid)
 		b.buf = pgio.AppendInt32(b.buf, -1)
 		b.fieldCount++
@@ -533,7 +533,7 @@ func (b *CompositeTextBuilder) AppendValue(oid uint32, field any) {
 		return
 	}
 
-	if field == nil {
+	if isNil, _ := isNilDriverValuer(field); isNil {
 		b.buf = append(b.buf, ',')
 		return
 	}

pgtype/composite_test.go

@@ -159,6 +159,160 @@ create type point3d as (
 	})
 }
 
+type parent struct {
+	Name     string
+	Location *point3d
+}
+
+func (p parent) IsNull() bool {
+	return false
+}
+
+func (p parent) Index(i int) any {
+	switch i {
+	case 0:
+		return p.Name
+	case 1:
+		return p.Location
+	default:
+		panic("invalid index")
+	}
+}
+
+func (p *parent) ScanNull() error {
+	return fmt.Errorf("cannot scan NULL into parent")
+}
+
+func (p *parent) ScanIndex(i int) any {
+	switch i {
+	case 0:
+		return &p.Name
+	case 1:
+		return &p.Location
+	default:
+		panic("invalid index")
+	}
+}
+
+// https://github.com/jackc/pgx/issues/2453
+func TestCompositeCodecTranscodeStructWithNilPointer(t *testing.T) {
+	defaultConnTestRunner.RunTest(context.Background(), t, func(ctx context.Context, t testing.TB, conn *pgx.Conn) {
+		_, err := conn.Exec(ctx, `drop type if exists parent;
+drop type if exists point3d;
+
+create type point3d as (
+	x float8,
+	y float8,
+	z float8
+);
+
+create type parent as (
+	name text,
+	location point3d
+);`)
+		require.NoError(t, err)
+		defer conn.Exec(ctx, "drop type parent")
+		defer conn.Exec(ctx, "drop type point3d")
+
+		dataTypes, err := conn.LoadTypes(ctx, []string{"point3d", "parent"})
+		require.NoError(t, err)
+		conn.TypeMap().RegisterTypes(dataTypes)
+
+		formats := []struct {
+			name string
+			code int16
+		}{
+			{name: "TextFormat", code: pgx.TextFormatCode},
+			{name: "BinaryFormat", code: pgx.BinaryFormatCode},
+		}
+
+		for _, format := range formats {
+			input := parent{Name: "test", Location: nil}
+			var output parent
+			err := conn.QueryRow(ctx, "select $1::parent", pgx.QueryResultFormats{format.code}, input).Scan(&output)
+			require.NoErrorf(t, err, "%v", format.name)
+			require.Equalf(t, input, output, "%v", format.name)
+		}
+	})
+}
+
+type parentWithSlice struct {
+	Name      string
+	Locations []*point3d
+}
+
+func (p parentWithSlice) IsNull() bool {
+	return false
+}
+
+func (p parentWithSlice) Index(i int) any {
+	switch i {
+	case 0:
+		return p.Name
+	case 1:
+		return p.Locations
+	default:
+		panic("invalid index")
+	}
+}
+
+func (p *parentWithSlice) ScanNull() error {
+	return fmt.Errorf("cannot scan NULL into parent")
+}
+
+func (p *parentWithSlice) ScanIndex(i int) any {
+	switch i {
+	case 0:
+		return &p.Name
+	case 1:
+		return &p.Locations
+	default:
+		panic("invalid index")
+	}
+}
+
+// https://github.com/jackc/pgx/issues/2453
+func TestCompositeCodecTranscodeStructWithSliceOfNilPointer(t *testing.T) {
+	defaultConnTestRunner.RunTest(context.Background(), t, func(ctx context.Context, t testing.TB, conn *pgx.Conn) {
+		_, err := conn.Exec(ctx, `drop type if exists parent;
+drop type if exists point3d;
+
+create type point3d as (
+	x float8,
+	y float8,
+	z float8
+);
+
+create type parent_with_slice as (
+	name text,
+	locations point3d[]
+);`)
+		require.NoError(t, err)
+		defer conn.Exec(ctx, "drop type parent_with_slice")
+		defer conn.Exec(ctx, "drop type point3d")
+
+		dataTypes, err := conn.LoadTypes(ctx, []string{"point3d", "parent_with_slice"})
+		require.NoError(t, err)
+		conn.TypeMap().RegisterTypes(dataTypes)
+
+		formats := []struct {
+			name string
+			code int16
+		}{
+			{name: "TextFormat", code: pgx.TextFormatCode},
+			{name: "BinaryFormat", code: pgx.BinaryFormatCode},
+		}
+
+		for _, format := range formats {
+			input := parentWithSlice{Name: "test", Locations: []*point3d{nil}}
+			var output parentWithSlice
+			err := conn.QueryRow(ctx, "select $1::parent_with_slice", pgx.QueryResultFormats{format.code}, input).Scan(&output)
+			require.NoErrorf(t, err, "%v", format.name)
+			require.Equalf(t, input, output, "%v", format.name)
+		}
+	})
+}
+
 func TestCompositeCodecDecodeValue(t *testing.T) {
 	defaultConnTestRunner.RunTest(context.Background(), t, func(ctx context.Context, t testing.TB, conn *pgx.Conn) {
 		_, err := conn.Exec(ctx, `drop type if exists point3d;