connection: returing ctx.Cause error in canceled case

Returing wrapped context.Cause(ctx) error in <-ctx.Done() case.
Allows compare errors using errors.Is/As.
Add 3 tests errors checking comparabily.

Fixes #457

Author: ermyar

CHANGELOG.md

@@ -17,6 +17,8 @@ Versioning](http://semver.org/spec/v2.0.0.html) except to the first release.
 
 * Required Go version is `1.24` now (#456).
 * `box.New` returns an error instead of panic (#448).
+* Now cases of `<-ctx.Done()` returns wrapped error provided by `ctx.Cause()`.
+  Allows you compare it using `errors.Is/As` (#457).
 
 ### Fixed
 

connection.go

@@ -984,7 +984,8 @@ 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, context.Cause(ctx)))
 			shard.rmut.Unlock()
 			return
 		default:
@@ -1026,7 +1027,8 @@ func (conn *Connection) contextWatchdog(fut *Future, ctx context.Context) {
 	case <-fut.done:
 		return
 	default:
-		conn.cancelFuture(fut, fmt.Errorf("context is done (request ID %d)", fut.requestId))
+		conn.cancelFuture(fut, fmt.Errorf("context is done (request ID %d): %w",
+			fut.requestId, context.Cause(ctx)))
 	}
 }
 

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): context deadline exceeded
 }
 
 func ExampleSelectRequest() {

tarantool_test.go

@@ -3,6 +3,7 @@ package tarantool_test
 import (
 	"context"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"io"
 	"log"
@@ -48,7 +49,8 @@ type Member struct {
 	Val   uint
 }
 
-var contextDoneErrRegexp = regexp.MustCompile(`^context is done \(request ID [0-9]+\)$`)
+var contextDoneErrRegexp = regexp.MustCompile(
+	`^context is done \(request ID [0-9]+\): context canceled$`)
 
 func (m *Member) EncodeMsgpack(e *msgpack.Encoder) error {
 	if err := e.EncodeArrayLen(2); err != nil {
@@ -2742,6 +2744,45 @@ func TestClientRequestObjectsWithPassedCanceledContext(t *testing.T) {
 	}
 }
 
+// Checking comparable with simple context.WithCancel.
+func TestComparableErrorsCanceledContext(t *testing.T) {
+	conn := test_helpers.ConnectWithValidation(t, dialer, opts)
+	defer conn.Close()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	req := NewPingRequest().Context(ctx)
+	cancel()
+	_, err := conn.Do(req).Get()
+	require.True(t, errors.Is(err, context.Canceled), err.Error())
+}
+
+// Checking comparable with simple context.WithTimeout.
+func TestComparableErrorsTimeoutContext(t *testing.T) {
+	conn := test_helpers.ConnectWithValidation(t, dialer, opts)
+	defer conn.Close()
+
+	timeout := time.Nanosecond
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	req := NewPingRequest().Context(ctx)
+	defer cancel()
+	_, err := conn.Do(req).Get()
+	require.True(t, errors.Is(err, context.DeadlineExceeded), err.Error())
+}
+
+// Checking comparable with context.WithCancelCause.
+// Shows ability to compare with custom errors (also with ClientError).
+func TestComparableErrorsCancelCauseContext(t *testing.T) {
+	conn := test_helpers.ConnectWithValidation(t, dialer, opts)
+	defer conn.Close()
+
+	ctxCause, cancelCause := context.WithCancelCause(context.Background())
+	req := NewPingRequest().Context(ctxCause)
+	cancelCause(ClientError{ErrConnectionClosed, "something went wrong"})
+	_, err := conn.Do(req).Get()
+	var tmpErr ClientError
+	require.True(t, errors.As(err, &tmpErr), tmpErr.Error())
+}
+
 // waitCtxRequest waits for the WaitGroup in Body() call and returns
 // the context from Ctx() call. The request helps us to make sure that
 // the context's cancel() call is called before a response received.