Fix:(issue_1500). Fix slice flag value duplication issue

app_test.go

@@ -956,6 +956,37 @@ func TestApp_UseShortOptionHandlingSubCommand_missing_value(t *testing.T) {
 	expect(t, err, errors.New("flag needs an argument: -n"))
 }
 
+func TestApp_UseShortOptionAfterSliceFlag(t *testing.T) {
+	var one, two bool
+	var name string
+	var sliceValDest StringSlice
+	var sliceVal []string
+	expected := "expectedName"
+
+	app := newTestApp()
+	app.UseShortOptionHandling = true
+	app.Flags = []Flag{
+		&StringSliceFlag{Name: "env", Aliases: []string{"e"}, Destination: &sliceValDest},
+		&BoolFlag{Name: "one", Aliases: []string{"o"}},
+		&BoolFlag{Name: "two", Aliases: []string{"t"}},
+		&StringFlag{Name: "name", Aliases: []string{"n"}},
+	}
+	app.Action = func(c *Context) error {
+		sliceVal = c.StringSlice("env")
+		one = c.Bool("one")
+		two = c.Bool("two")
+		name = c.String("name")
+		return nil
+	}
+
+	_ = app.Run([]string{"", "-e", "foo", "-on", expected})
+	expect(t, sliceVal, []string{"foo"})
+	expect(t, sliceValDest.Value(), []string{"foo"})
+	expect(t, one, true)
+	expect(t, two, false)
+	expect(t, name, expected)
+}
+
 func TestApp_Float64Flag(t *testing.T) {
 	var meters float64
 

parse.go

@@ -46,7 +46,10 @@ func parseIter(set *flag.FlagSet, ip iterativeParser, args []string, shellComple
 			}
 
 			// swap current argument with the split version
-			args = append(args[:i], append(shortOpts, args[i+1:]...)...)
+			// do not include args that parsed correctly so far as it would
+			// trigger Value.Set() on those args and would result in
+			// duplicates for slice type flags
+			args = append(shortOpts, args[i+1:]...)
 			argsWereSplit = true
 			break
 		}
@@ -56,13 +59,6 @@ func parseIter(set *flag.FlagSet, ip iterativeParser, args []string, shellComple
 		if !argsWereSplit {
 			return err
 		}
-
-		// Since custom parsing failed, replace the flag set before retrying
-		newSet, err := ip.newFlagSet()
-		if err != nil {
-			return err
-		}
-		*set = *newSet
 	}
 }