factor flag error handling into function

cmd/leagueflag.go

@@ -16,8 +16,6 @@ this program. If not, see <http://www.gnu.org/licenses/>.
 package cmd
 
 import (
-	"errors"
-	"sort"
 	"strings"
 
 	"scm.dairydemon.net/filifa/mlblive/cmd/internal/statsapi"
@@ -56,10 +54,8 @@ func (t *leagueFlag) Set(v string) error {
 
 	_, ok := leagueIDs[v]
 	if !ok {
-		allowed := allowedFlags(leagueIDs)
+		allowed := keys(leagueIDs)
-		sort.Strings(allowed)
+		err = flagValueError("league", allowed)
-		allowedList := strings.Join(allowed, ", ")
-		err = errors.New("league must be one of " + allowedList)
 	} else {
 		*t = leagueFlag(v)
 	}

cmd/sportflag.go

@@ -16,8 +16,6 @@ this program. If not, see <http://www.gnu.org/licenses/>.
 package cmd
 
 import (
-	"errors"
-	"sort"
 	"strings"
 
 	"scm.dairydemon.net/filifa/mlblive/cmd/internal/statsapi"
@@ -61,10 +59,8 @@ func (t *sportFlag) Set(v string) error {
 
 	_, ok := sportIDs[v]
 	if !ok {
-		allowed := allowedFlags(sportIDs)
+		allowed := keys(sportIDs)
-		sort.Strings(allowed)
+		err = flagValueError("sport", allowed)
-		allowedList := strings.Join(allowed, ", ")
-		err = errors.New("sport must be one of " + allowedList)
 	} else {
 		*t = sportFlag(v)
 	}

cmd/teamflag.go

@@ -56,7 +56,7 @@ var teamIDs = map[string]statsapi.TeamID{
 	"mil": statsapi.MIL,
 }
 
-func allowedFlags[V any](m map[string]V) []string {
+func keys[V any](m map[string]V) []string {
 	keys := make([]string, len(m))
 
 	i := 0
@@ -68,6 +68,12 @@ func allowedFlags[V any](m map[string]V) []string {
 	return keys
 }
 
+func flagValueError(name string, allowed []string) error {
+	sort.Strings(allowed)
+	allowedList := strings.Join(allowed, ", ")
+	return errors.New(name + " must be one of " + allowedList)
+}
+
 type teamFlag string
 
 func (t *teamFlag) String() string {
@@ -85,10 +91,8 @@ func (t *teamFlag) Set(v string) error {
 
 	_, ok := teamIDs[v]
 	if !ok {
-		allowed := allowedFlags(teamIDs)
+		allowed := keys(teamIDs)
-		sort.Strings(allowed)
+		err = flagValueError("team", allowed)
-		allowedList := strings.Join(allowed, ", ")
-		err = errors.New("team must be one of " + allowedList)
 	} else {
 		*t = teamFlag(v)
 	}