display valid flag values on error

cmd/leagueflag.go

@@ -55,7 +55,9 @@ func (t *leagueFlag) Set(v string) error {
 
 	_, ok := leagueIDs[v]
 	if !ok {
-		err = errors.New("invalid league ID")
+		allowed := allowedFlags(leagueIDs)
+		allowedList := strings.Join(allowed, ", ")
+		err = errors.New("league must be one of " + allowedList)
 	} else {
 		*t = leagueFlag(v)
 	}

cmd/schedule.go

@@ -93,7 +93,7 @@ func init() {
 
 	// Cobra supports local flags which will only run when this command
 	// is called directly, e.g.:
-	scheduleCmd.Flags().VarP(&team, "team", "t", "team to get schedule for (atl, az, bal, bos, chc, cin, cle, col, cws, det, hou, kc, laa, lad, mia, mil, min, nym, nyy, oak, phi, pit, sd, sea, sf, stl, tb, tex, tor, wsh)")
+	scheduleCmd.Flags().VarP(&team, "team", "t", "team to get schedule for")
 	scheduleCmd.Flags().StringVarP(&date, "date", "d", "", "date to get schedule for (YYYY-MM-DD)")
-	scheduleCmd.Flags().StringVarP(&sport, "sport", "s", "mlb", "sport to get schedule for (default: MLB)")
+	scheduleCmd.Flags().StringVarP(&sport, "sport", "s", "mlb", "sport to get schedule for")
 }

cmd/teamflag.go

@@ -55,6 +55,18 @@ var teamIDs = map[string]statsapi.TeamID{
 	"mil": statsapi.MIL,
 }
 
+func allowedFlags[V any](m map[string]V) []string {
+	keys := make([]string, len(m))
+
+	i := 0
+	for k := range m {
+		keys[i] = k
+		i++
+	}
+
+	return keys
+}
+
 type teamFlag string
 
 func (t *teamFlag) String() string {
@@ -72,7 +84,9 @@ func (t *teamFlag) Set(v string) error {
 
 	_, ok := teamIDs[v]
 	if !ok {
-		err = errors.New("invalid team ID")
+		allowed := allowedFlags(teamIDs)
+		allowedList := strings.Join(allowed, ", ")
+		err = errors.New("team must be one of " + allowedList)
 	} else {
 		*t = teamFlag(v)
 	}