fix logging of application errors

internal/qerr/quic_error.go

@@ -7,9 +7,10 @@ import (
 
 // A QuicError consists of an error code plus a error reason
 type QuicError struct {
-	ErrorCode    ErrorCode
-	ErrorMessage string
-	isTimeout    bool
+	ErrorCode          ErrorCode
+	ErrorMessage       string
+	isTimeout          bool
+	isApplicationError bool
 }
 
 var _ net.Error = &QuicError{}
@@ -38,7 +39,21 @@ func CryptoError(tlsAlert uint8, errorMessage string) *QuicError {
 	}
 }
 
+func ApplicationError(errorCode ErrorCode, errorMessage string) *QuicError {
+	return &QuicError{
+		ErrorCode:          errorCode,
+		ErrorMessage:       errorMessage,
+		isApplicationError: true,
+	}
+}
+
 func (e *QuicError) Error() string {
+	if e.isApplicationError {
+		if len(e.ErrorMessage) == 0 {
+			return fmt.Sprintf("Application error %#x", uint64(e.ErrorCode))
+		}
+		return fmt.Sprintf("Application error %#x: %s", uint64(e.ErrorCode), e.ErrorMessage)
+	}
 	if len(e.ErrorMessage) == 0 {
 		return e.ErrorCode.Error()
 	}

internal/qerr/quic_error_test.go

@@ -26,12 +26,12 @@ var _ = Describe("QUIC Transport Errors", func() {
 	})
 
 	Context("crypto errors", func() {
-		It("has a string representation for crypto errors with a message", func() {
+		It("has a string representation for errors with a message", func() {
 			err := CryptoError(42, "foobar")
 			Expect(err.Error()).To(Equal("CRYPTO_ERROR: foobar"))
 		})
 
-		It("has a string representation for crypto errors without a message", func() {
+		It("has a string representation for errors without a message", func() {
 			err := CryptoError(42, "")
 			Expect(err.Error()).To(Equal("CRYPTO_ERROR: tls: bad certificate"))
 		})
@@ -42,6 +42,18 @@ var _ = Describe("QUIC Transport Errors", func() {
 		})
 	})
 
+	Context("application errors", func() {
+		It("has a string representation for errors with a message", func() {
+			err := ApplicationError(0x42, "foobar")
+			Expect(err.Error()).To(Equal("Application error 0x42: foobar"))
+		})
+
+		It("has a string representation for errors without a message", func() {
+			err := ApplicationError(0x42, "")
+			Expect(err.Error()).To(Equal("Application error 0x42"))
+		})
+	})
+
 	Context("ErrorCode", func() {
 		It("works as error", func() {
 			var err error = StreamStateError