go/proto/msgpack: Simplify debugging by printing function name in case of overflow

go/neo/proto/msgpack.go

@@ -44,7 +44,7 @@ func (e *mstructDecodeError) Error() string {
 // mdecodeErr is called to normilize error when msgp.ReadXXX returns err when decoding path.
 func mdecodeErr(path string, err error) error {
 	if err == msgp.ErrShortBytes {
-		return ErrDecodeOverflow
+		return &ErrDecodeOverflow{path}
 	}
 	return &mdecodeError{path, err}
 }

go/neo/proto/proto-misc.go

@@ -228,3 +228,12 @@ func (addr Address) String() string {
 		return net.JoinHostPort(addr.Host, fmt.Sprintf("%d", addr.Port))
 	}
 }
+
+// ErrDecodeOverflow is the error returned by neoMsgDecode when decoding hits buffer overflow
+type ErrDecodeOverflow struct {
+	function string
+}
+
+func (e *ErrDecodeOverflow) Error() string {
+	return fmt.Sprintf("decode '%s': buffer overflow", e.function)
+}

go/neo/proto/proto.go

@@ -70,7 +70,6 @@ import (
 	"lab.nexedi.com/kirr/neo/go/internal/packed"
 
 	"encoding/binary"
-	"errors"
 	"math"
 )
 
@@ -168,9 +167,6 @@ func (e Encoding) MsgDecode(msg Msg, data []byte) (nread int, err error) {
 }
 
 
-// ErrDecodeOverflow is the error returned by neoMsgDecode when decoding hits buffer overflow
-var ErrDecodeOverflow = errors.New("decode: buffer overflow")
-
 // ---- messages ----
 
 //neo:proto enum

go/neo/proto/proto_test.go

@@ -22,6 +22,7 @@ package proto
 
 import (
 	"encoding/binary"
+	"errors"
 	hexpkg "encoding/hex"
 	"fmt"
 	"reflect"
@@ -152,7 +153,8 @@ func testMsgMarshal(t *testing.T, enc Encoding, msg Msg, encoded string) {
 	// decode must detect buffer overflow
 	for l := len(encoded) - 1; l >= 0; l-- {
 		n, err = enc.MsgDecode(msg2, data[:l])
-		if !(n == 0 && err == ErrDecodeOverflow) {
+		errDecodeOverflow := new(ErrDecodeOverflow)
+		if !(n == 0 && errors.As(err, &errDecodeOverflow)) {
 			t.Errorf("%c/%v: decode overflow not detected on [:%v]", enc, typ, l)
 		}
 
@@ -429,9 +431,10 @@ func TestMsgDecodeLenOverflowN(t *testing.T) {
 			}()
 
 			n, err := enc.MsgDecode(tt.msg, data)
-			if !(n == 0 && err == ErrDecodeOverflow) {
+			errDecodeOverflow := new(ErrDecodeOverflow)
+			if !(n == 0 && errors.As(err, &errDecodeOverflow)) {
 				t.Errorf("%T: decode %x\nhave: %d, %v\nwant: %d, %v", tt.msg, data,
-					n, err, 0, ErrDecodeOverflow)
+					n, err, 0, errDecodeOverflow)
 			}
 		}()
 	}

go/neo/proto/protogen.go

@@ -320,6 +320,7 @@ package proto
 
 import (
 	"encoding/binary"
+	"errors"
 	"math"
 	"reflect"
 	"sort"
@@ -917,7 +918,7 @@ func (d *decoderCommon) generatedCode() string {
 	// NOTE for >0 check actual X in StdSizes{X} does not particularly matter
 	if ((&types.StdSizes{8, 8}).Sizeof(d.typ) > 0 || d.enc != 'N') && d.overflow.gotoEmitted {
 		code.emit("\noverflow:")
-		code.emit("return 0, ErrDecodeOverflow")
+		code.emit("return 0, &ErrDecodeOverflow{\"%s\"}", d.typeName)
 	}
 	code.emit("}\n")
 
@@ -1155,7 +1156,8 @@ func (d *decoderM) genBasic(assignto string, typ *types.Basic, userType types.Ty
 			// correct float, but data is too short - catch this to return
 			// 'ErrDecodeOverflow' instead of type error.
 			d.emit("  err = mdecodeErr(%q, err)", d.pathName(assignto))
-			d.emit("  if err == ErrDecodeOverflow {")
+			d.emit("  errDecodeOverflow := new(ErrDecodeOverflow)")
+			d.emit("  if errors.As(err, &errDecodeOverflow) {")
 			d.emit("  	return 0, err")
 			d.emit("  }")
 			d.emit("  tail, err = msgp.ReadNilBytes(data)")