status: handle wrapped errors

status/status.go

@@ -77,7 +77,8 @@ func FromProto(s *spb.Status) *Status {
 // FromError returns a Status representation of err.
 //
 //   - If err was produced by this package or implements the method `GRPCStatus()
-//     *Status`, the appropriate Status is returned.
+//     *Status`, or if err wraps a type satisfying this, the appropriate Status is
+//     returned.
 //
 //   - If err is nil, a Status is returned with codes.OK and no message.
 //
@@ -88,9 +89,8 @@ func FromError(err error) (s *Status, ok bool) {
 	if err == nil {
 		return nil, true
 	}
-	if se, ok := err.(interface {
-		GRPCStatus() *Status
-	}); ok {
+	var se interface{ GRPCStatus() *Status }
+	if errors.As(err, &se) {
 		return se.GRPCStatus(), true
 	}
 	return New(codes.Unknown, err.Error()), false
@@ -103,19 +103,16 @@ func Convert(err error) *Status {
 	return s
 }
 
-// Code returns the Code of the error if it is a Status error, codes.OK if err
-// is nil, or codes.Unknown otherwise.
+// Code returns the Code of the error if it is a Status error or if it wraps a
+// Status error. If that is not the case, it returns codes.OK if err is nil, or
+// codes.Unknown otherwise.
 func Code(err error) codes.Code {
 	// Don't use FromError to avoid allocation of OK status.
 	if err == nil {
 		return codes.OK
 	}
-	if se, ok := err.(interface {
-		GRPCStatus() *Status
-	}); ok {
-		return se.GRPCStatus().Code()
-	}
-	return codes.Unknown
+
+	return Convert(err).Code()
 }
 
 // FromContextError converts a context error or wrapped context error into a

status/status_test.go

@@ -32,6 +32,7 @@ import (
 	cpb "google.golang.org/genproto/googleapis/rpc/code"
 	epb "google.golang.org/genproto/googleapis/rpc/errdetails"
 	spb "google.golang.org/genproto/googleapis/rpc/status"
+
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/internal/grpctest"
 	"google.golang.org/grpc/internal/status"
@@ -192,6 +193,70 @@ func (s) TestFromErrorUnknownError(t *testing.T) {
 	}
 }
 
+func (s) TestFromErrorWrapped(t *testing.T) {
+	const code, message = codes.Internal, "test description"
+	err := fmt.Errorf("wrapped error: %w", Error(code, message))
+	s, ok := FromError(err)
+	if !ok || s.Code() != code || s.Message() != message || s.Err() == nil {
+		t.Fatalf("FromError(%v) = %v, %v; want <Code()=%s, Message()=%q, Err()!=nil>, true", err, s, ok, code, message)
+	}
+}
+
+func (s) TestFromErrorImplementsInterfaceWrapped(t *testing.T) {
+	const code, message = codes.Internal, "test description"
+	err := fmt.Errorf("wrapped error: %w", customError{Code: code, Message: message})
+	s, ok := FromError(err)
+	if !ok || s.Code() != code || s.Message() != message || s.Err() == nil {
+		t.Fatalf("FromError(%v) = %v, %v; want <Code()=%s, Message()=%q, Err()!=nil>, true", err, s, ok, code, message)
+	}
+}
+
+func (s) TestCode(t *testing.T) {
+	const code = codes.Internal
+	err := Error(code, "test description")
+	if s := Code(err); s != code {
+		t.Fatalf("Code(%v) = %v; want <Code()=%s>", err, s, code)
+	}
+}
+
+func (s) TestCodeOK(t *testing.T) {
+	if s, code := Code(nil), codes.OK; s != code {
+		t.Fatalf("Code(%v) = %v; want <Code()=%s>", nil, s, code)
+	}
+}
+
+func (s) TestCodeImplementsInterface(t *testing.T) {
+	const code = codes.Internal
+	err := customError{Code: code, Message: "test description"}
+	if s := Code(err); s != code {
+		t.Fatalf("Code(%v) = %v; want <Code()=%s>", err, s, code)
+	}
+}
+
+func (s) TestCodeUnknownError(t *testing.T) {
+	const code = codes.Unknown
+	err := errors.New("unknown error")
+	if s := Code(err); s != code {
+		t.Fatalf("Code(%v) = %v; want <Code()=%s>", err, s, code)
+	}
+}
+
+func (s) TestCodeWrapped(t *testing.T) {
+	const code = codes.Internal
+	err := fmt.Errorf("wrapped: %w", Error(code, "test description"))
+	if s := Code(err); s != code {
+		t.Fatalf("Code(%v) = %v; want <Code()=%s>", err, s, code)
+	}
+}
+
+func (s) TestCodeImplementsInterfaceWrapped(t *testing.T) {
+	const code = codes.Internal
+	err := fmt.Errorf("wrapped: %w", customError{Code: code, Message: "test description"})
+	if s := Code(err); s != code {
+		t.Fatalf("Code(%v) = %v; want <Code()=%s>", err, s, code)
+	}
+}
+
 func (s) TestConvertKnownError(t *testing.T) {
 	code, message := codes.Internal, "test description"
 	err := Error(code, message)