From 4995a3e9cc2102264d261ecf6350a612ea05eb87 Mon Sep 17 00:00:00 2001
From: Albert Nigmatzianov <albertnigma@gmail.com>
Date: Wed, 19 Apr 2017 10:47:10 +0200
Subject: Make more detailed error in Set

---
 flag.go | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/flag.go b/flag.go
index 04f6594..8a8c89c 100644
--- a/flag.go
+++ b/flag.go
@@ -408,7 +408,13 @@ func (f *FlagSet) Set(name, value string) error {
 	}
 	err := flag.Value.Set(value)
 	if err != nil {
-		return err
+		var flagName string
+		if len(flag.Shorthand) > 0 && len(flag.ShorthandDeprecated) == 0 {
+			flagName = fmt.Sprintf("-%s, --%s", flag.Shorthand, flag.Name)
+		} else {
+			flagName = fmt.Sprintf("--%s", flag.Name)
+		}
+		return fmt.Errorf("invalid argument %q for %q flag: %v", value, flagName, err)
 	}
 	if f.actual == nil {
 		f.actual = make(map[NormalizedName]*Flag)
-- 
cgit v1.2.3