Add .String() func

Signed-off-by: Tim Vaillancourt <tim@timvaillancourt.com>

go/vt/topo/wildcards.go

@@ -24,6 +24,7 @@ import (
 	"context"
 
 	"vitess.io/vitess/go/vt/proto/vtrpc"
+	"vitess.io/vitess/go/vt/topo/topoproto"
 	"vitess.io/vitess/go/vt/vterrors"
 
 	"vitess.io/vitess/go/fileutil"
@@ -64,6 +65,10 @@ type KeyspaceShard struct {
 	Shard    string
 }
 
+func (ks KeyspaceShard) String() string {
+	return topoproto.KeyspaceShardString(ks.Keyspace, ks.Shard)
+}
+
 // ResolveShardWildcard will resolve shard wildcards. Both keyspace and shard
 // names can use wildcard. Errors talking to the topology server are returned.
 // ErrNoNode is ignored if it's the result of resolving a wildcard. Examples:

go/vt/vtorc/logic/tablet_discovery.go

@@ -158,10 +158,7 @@ func getKeyspaceShardsToWatch() ([]*topo.KeyspaceShard, error) {
 	}
 
 	slices.SortStableFunc(keyspaceShards, func(a, b *topo.KeyspaceShard) int {
-		return strings.Compare(
-			topoproto.KeyspaceShardString(a.Keyspace, a.Shard),
-			topoproto.KeyspaceShardString(b.Keyspace, b.Shard),
-		)
+		return strings.Compare(a.String(), b.String())
 	})
 
 	return keyspaceShards, nil