Config set adds only unique values

internal/algorithms/slices.go

@@ -71,3 +71,17 @@ func NotEquals[T comparable](value T) Matcher[T] {
 		return x != value
 	}
 }
+
+// Uniq return a copy of the input array with all duplicates removed
+func Uniq[T comparable](in []T) []T {
+	have := map[T]bool{}
+	var out []T
+	for _, v := range in {
+		if have[v] {
+			continue
+		}
+		out = append(out, v)
+		have[v] = true
+	}
+	return out
+}

internal/cli/config/set.go

@@ -20,6 +20,7 @@ import (
 	"encoding/json"
 	"os"
 
+	f "github.com/arduino/arduino-cli/internal/algorithms"
 	"github.com/arduino/arduino-cli/internal/cli/feedback"
 	rpc "github.com/arduino/arduino-cli/rpc/cc/arduino/cli/commands/v1"
 	"github.com/sirupsen/logrus"
@@ -59,8 +60,8 @@ func runSetCommand(ctx context.Context, srv rpc.ArduinoCoreServiceServer, args [
 		req.EncodedValue = args[1]
 		req.ValueFormat = "cli"
 	} else {
-		// Array
-		jsonValues, err := json.Marshal(args[1:])
+		// Uniq Array
+		jsonValues, err := json.Marshal(f.Uniq(args[1:]))
 		if err != nil {
 			feedback.Fatal(tr("Error setting value: %v", err), feedback.ErrGeneric)
 		}