pkg/kv/kvpb: Add SafeFormat method to BatchResponse struct

This patch helps to fix the overly redacted log line on instances where BatchResponse
is logged. Implemented a SafeFormat function on BatchResponse struct which overrides
the String() method when its object is logged.

Epic: CRDB-37533
Part of: CRDB-44885
Release note: None

Author: Abhinav1299

pkg/kv/kvclient/kvcoord/dist_sender_test.go

@@ -4769,26 +4769,26 @@ func TestDistSenderSlowLogMessage(t *testing.T) {
 	br.Error = kvpb.NewError(errors.New("boom"))
 	desc := &roachpb.RangeDescriptor{RangeID: 9, StartKey: roachpb.RKey("x"), EndKey: roachpb.RKey("z")}
 	{
-		exp := `have been waiting 8.16s (120 attempts) for RPC Get(Shared,Unreplicated) [‹"a"›] to` +
-			` r9:‹{x-z}› [<no replicas>, next=0, gen=0]; resp: ‹(err: boom)›`
+		exp := `have been waiting 8.16s (120 attempts) for RPC Get(Shared,Unreplicated) ["a"] to` +
+			` r9:{x-z} [<no replicas>, next=0, gen=0]; resp: (err: boom)`
 		var s redact.StringBuilder
 		slowRangeRPCWarningStr(&s, ba, dur, attempts, desc, nil /* err */, br)
-		act := s.RedactableString()
+		act := s.RedactableString().StripMarkers()
 		require.EqualValues(t, exp, act)
 	}
 	{
 		exp := `slow RPC finished after 8.16s (120 attempts)`
 		var s redact.StringBuilder
 		slowRangeRPCReturnWarningStr(&s, dur, attempts)
-		act := s.RedactableString()
+		act := s.RedactableString().StripMarkers()
 		require.EqualValues(t, exp, act)
 	}
 	{
-		exp := `have been waiting 8.16s (120 attempts) for RPC Get(Shared,Unreplicated) [‹"a"›] to` +
-			` replica (n2,s3):1; resp: ‹(err: boom)›`
+		exp := `have been waiting 8.16s (120 attempts) for RPC Get(Shared,Unreplicated) ["a"] to` +
+			` replica (n2,s3):1; resp: (err: boom)`
 		var s redact.StringBuilder
 		slowReplicaRPCWarningStr(&s, ba, dur, attempts, nil /* err */, br)
-		act := s.RedactableString()
+		act := s.RedactableString().StripMarkers()
 		require.EqualValues(t, exp, act)
 	}
 }

pkg/kv/kvpb/batch.go

@@ -453,20 +453,26 @@ func (ba *BatchRequest) GetArg(method Method) (Request, bool) {
 }
 
 func (br *BatchResponse) String() string {
-	var str []string
-	str = append(str, fmt.Sprintf("(err: %v)", br.Error))
+	return redact.StringWithoutMarkers(br)
+}
+
+// SafeFormat implements the redact.SafeFormatter interface.
+func (br *BatchResponse) SafeFormat(s redact.SafePrinter, verb rune) {
+	// Marking Error of BatchResponse as safe as Outside of the RPC boundaries,
+	// this field is nil and must neither be checked nor populated
+	s.Printf("(err: %s)", redact.Safe(br.Error.String()))
+
 	for count, union := range br.Responses {
 		// Limit the strings to provide just a summary. Without this limit a log
 		// message with a BatchResponse can be very long.
 		if count >= 20 && count < len(br.Responses)-5 {
 			if count == 20 {
-				str = append(str, fmt.Sprintf("... %d skipped ...", len(br.Responses)-25))
+				s.Printf(", ... %d skipped ...", len(br.Responses)-25)
 			}
 			continue
 		}
-		str = append(str, fmt.Sprintf("%T", union.GetInner()))
+		s.Printf(", %T", redact.Safe(union.GetInner()))
 	}
-	return strings.Join(str, ", ")
 }
 
 // LockSpanIterate calls LockSpanIterate for each request in the batch.