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
 

flag.go

@@ -126,6 +126,21 @@ type Flag interface {
 	RunAction(*Context) error
 }
 
+// DocGenerationFlag is an interface that allows documentation generation for the flag
+type DocGenerationFlag interface {
+	Flag
+
+	// TakesValue returns true if the flag takes a value, otherwise false
+	TakesValue() bool
+
+	// GetValue returns the flags value as string representation and an empty
+	// string if the flag takes no value at all.
+	GetValue() string
+
+	// GetEnvVars returns the env vars for this flag
+	GetEnvVars() []string
+}
+
 // DocGenerationSliceFlag extends DocGenerationFlag for slice-based flags.
 type DocGenerationSliceFlag interface {
 	DocGenerationFlag
@@ -293,8 +308,14 @@ func formatDefault(format string) string {
 }
 
 func stringifyFlag(f Flag) string {
-	placeholder, usage := unquoteUsage(f.GetUsage())
-	needsPlaceholder := f.TakesValue()
+	// enforce DocGeneration interface on flags to avoid reflection
+	df, ok := f.(DocGenerationFlag)
+	if !ok {
+		return ""
+	}
+
+	placeholder, usage := unquoteUsage(df.GetUsage())
+	needsPlaceholder := df.TakesValue()
 
 	if needsPlaceholder && placeholder == "" {
 		placeholder = defaultPlaceholder
@@ -302,7 +323,7 @@ func stringifyFlag(f Flag) string {
 
 	defaultValueString := ""
 
-	if s := f.GetDefaultText(); s != "" {
+	if s := df.GetDefaultText(); s != "" {
 		defaultValueString = fmt.Sprintf(formatDefault("%s"), s)
 	}
 

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
 		}