errors: added CodeErrors

Revised error use, added new type CodeErrors to compare them using
errors.Is(). Also used to check that request's ctx was cancelled.

Fixes (#457)

Author: ermyar

connection.go

@@ -984,7 +984,7 @@ func (conn *Connection) newFuture(req Request) (fut *Future) {
 	if ctx != nil {
 		select {
 		case <-ctx.Done():
-			fut.SetError(fmt.Errorf("context is done (request ID %d)", fut.requestId))
+			fut.SetError(fmt.Errorf("context is done (request ID %d) (%w)", fut.requestId, ErrCancelledCtx))
 			shard.rmut.Unlock()
 			return
 		default:

errors.go

@@ -25,13 +25,13 @@ func (tnterr Error) Error() string {
 // ClientError is connection error produced by this client,
 // i.e. connection failures or timeouts.
 type ClientError struct {
-	Code uint32
+	Code CodeError
 	Msg  string
 }
 
 // Error converts a ClientError to a string.
 func (clierr ClientError) Error() string {
-	return fmt.Sprintf("%s (0x%x)", clierr.Msg, clierr.Code)
+	return fmt.Sprintf("%s (0x%x)", clierr.Msg, uint32(clierr.Code))
 }
 
 // Temporary returns true if next attempt to perform request may succeeded.
@@ -52,13 +52,22 @@ func (clierr ClientError) Temporary() bool {
 	}
 }
 
+// CodeError is an error providing code of failure, to distinct them using errors.Is.
+type CodeError uint32
+
+// Error converts CodeError to a string.
+func (err CodeError) Error() string {
+	return fmt.Sprintf("0x%x", uint32(err))
+}
+
 // Tarantool client error codes.
 const (
-	ErrConnectionNotReady = 0x4000 + iota
-	ErrConnectionClosed   = 0x4000 + iota
-	ErrProtocolError      = 0x4000 + iota
-	ErrTimeouted          = 0x4000 + iota
-	ErrRateLimited        = 0x4000 + iota
-	ErrConnectionShutdown = 0x4000 + iota
-	ErrIoError            = 0x4000 + iota
+	ErrConnectionNotReady CodeError = 0x4000 + iota
+	ErrConnectionClosed
+	ErrProtocolError
+	ErrTimeouted
+	ErrRateLimited
+	ErrConnectionShutdown
+	ErrIoError
+	ErrCancelledCtx
 )

example_test.go

@@ -167,7 +167,7 @@ func ExamplePingRequest_Context() {
 	fmt.Println("Ping Error", regexp.MustCompile("[0-9]+").ReplaceAllString(err.Error(), "N"))
 	// Output:
 	// Ping Resp data []
-	// Ping Error context is done (request ID N)
+	// Ping Error context is done (request ID N) (NxN)
 }
 
 func ExampleSelectRequest() {

tarantool_test.go

@@ -3,6 +3,7 @@ package tarantool_test
 import (
 	"context"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"io"
 	"log"
@@ -48,7 +49,7 @@ type Member struct {
 	Val   uint
 }
 
-var contextDoneErrRegexp = regexp.MustCompile(`^context is done \(request ID [0-9]+\)$`)
+var contextDoneErrRegexp = regexp.MustCompile(fmt.Sprintf(`^context is done \(request ID [0-9]+\) \(%s\)$`, ErrCancelledCtx.Error()))
 
 func (m *Member) EncodeMsgpack(e *msgpack.Encoder) error {
 	if err := e.EncodeArrayLen(2); err != nil {
@@ -2737,6 +2738,8 @@ func TestClientRequestObjectsWithPassedCanceledContext(t *testing.T) {
 	if !contextDoneErrRegexp.Match([]byte(err.Error())) {
 		t.Fatalf("Failed to catch an error from done context")
 	}
+	// checking that we could use errors.Is to get known about error.
+	require.True(t, errors.Is(err, ErrCancelledCtx))
 	if resp != nil {
 		t.Fatalf("Response is not nil after the occurred error")
 	}
@@ -3298,6 +3301,7 @@ func TestClientIdRequestObjectWithPassedCanceledContext(t *testing.T) {
 	resp, err := conn.Do(req).Get()
 	require.Nilf(t, resp, "Response is empty")
 	require.NotNilf(t, err, "Error is not empty")
+	require.True(t, errors.Is(err, ErrCancelledCtx))
 	require.Regexp(t, contextDoneErrRegexp, err.Error())
 }