Fixes #1648

This adds a new field to the `FlagStringSlice` struct for controlling
the trimming of space when parsing arguments. The new field is called
`NoTrimSpace` and trims space by default. This is to not break existing
programs that depends on this behavior. See
#1649 (comment) for
further details.

app_test.go

@@ -428,7 +428,7 @@ func ExampleApp_Run_sliceValues() {
 	// 0-float64Sclice cli.Float64Slice{slice:[]float64{13.3, 14.4, 15.5, 16.6}, separator:cli.separatorSpec{sep:"", disabled:false, customized:false}, hasBeenSet:true}
 	// 1-int64Sclice cli.Int64Slice{slice:[]int64{13, 14, 15, 16}, separator:cli.separatorSpec{sep:"", disabled:false, customized:false}, hasBeenSet:true}
 	// 2-intSclice cli.IntSlice{slice:[]int{13, 14, 15, 16}, separator:cli.separatorSpec{sep:"", disabled:false, customized:false}, hasBeenSet:true}
-	// 3-stringSclice cli.StringSlice{slice:[]string{"parsed1", "parsed2", "parsed3", "parsed4"}, separator:cli.separatorSpec{sep:"", disabled:false, customized:false}, hasBeenSet:true}
+	// 3-stringSclice cli.StringSlice{slice:[]string{"parsed1", "parsed2", "parsed3", "parsed4"}, separator:cli.separatorSpec{sep:"", disabled:false, customized:false}, hasBeenSet:true, noTrimSpace:false}
 	// error: <nil>
 }
 

flag-spec.yaml

@@ -101,6 +101,8 @@ flag_types:
         type: bool
       - name: Action
         type: "func(*Context, []string) error"
+      - name: NoTrimSpace
+        type: bool
   time.Duration:
     struct_fields:
       - name: Action

flag_string_slice.go

@@ -10,9 +10,10 @@ import (
 
 // StringSlice wraps a []string to satisfy flag.Value
 type StringSlice struct {
-	slice      []string
-	separator  separatorSpec
-	hasBeenSet bool
+	slice       []string
+	separator   separatorSpec
+	hasBeenSet  bool
+	noTrimSpace bool
 }
 
 // NewStringSlice creates a *StringSlice with default values
@@ -45,6 +46,9 @@ func (s *StringSlice) Set(value string) error {
 	}
 
 	for _, t := range s.separator.flagSplitMultiValues(value) {
+		if !s.noTrimSpace {
+			t = strings.TrimSpace(t)
+		}
 		s.slice = append(s.slice, t)
 	}
 
@@ -149,6 +153,8 @@ func (f *StringSliceFlag) Apply(set *flag.FlagSet) error {
 		setValue.WithSeparatorSpec(f.separator)
 	}
 
+	setValue.noTrimSpace = f.NoTrimSpace
+
 	if val, source, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
 		for _, s := range f.separator.flagSplitMultiValues(val) {
 			if err := setValue.Set(strings.TrimSpace(s)); err != nil {

flag_test.go

@@ -774,7 +774,7 @@ func TestStringSliceFlag_MatchStringFlagBehavior(t *testing.T) {
 			app := App{
 				Flags: []Flag{
 					&StringFlag{Name: "string"},
-					&StringSliceFlag{Name: "slice"},
+					&StringSliceFlag{Name: "slice", NoTrimSpace: true},
 				},
 				Action: func(ctx *Context) error {
 					f1, f2 := ctx.String("string"), ctx.StringSlice("slice")
@@ -797,6 +797,52 @@ func TestStringSliceFlag_MatchStringFlagBehavior(t *testing.T) {
 	}
 }
 
+func TestStringSliceFlag_TrimSpace(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		in, out string
+	}{
+		{" asd", "asd"},
+		{"123 ", "123"},
+		{" asd ", "asd"},
+	}
+	for testNum, tt := range tests {
+		tt := tt
+		t.Run(fmt.Sprintf("%d", testNum), func(t *testing.T) {
+			t.Parallel()
+
+			app := App{
+				Flags: []Flag{
+					&StringSliceFlag{Name: "trim"},
+					&StringSliceFlag{Name: "no-trim", NoTrimSpace: true},
+				},
+				Action: func(ctx *Context) error {
+					flagTrim, flagNoTrim := ctx.StringSlice("trim"), ctx.StringSlice("no-trim")
+					if l := len(flagTrim); l != 1 {
+						t.Fatalf("slice flag 'trim' should result in exactly one value, got %d", l)
+					}
+					if l := len(flagNoTrim); l != 1 {
+						t.Fatalf("slice flag 'no-trim' should result in exactly one value, got %d", l)
+					}
+
+					if v := flagTrim[0]; v != tt.out {
+						t.Errorf("Expected trimmed value %q, got %q", tt.out, v)
+					}
+					if v := flagNoTrim[0]; v != tt.in {
+						t.Errorf("Expected no trimmed value%q, got %q", tt.out, v)
+					}
+					return nil
+				},
+			}
+
+			if err := app.Run([]string{"", "--trim", tt.in, "--no-trim", tt.in}); err != nil {
+				t.Errorf("app run error: %s", err)
+			}
+		})
+	}
+}
+
 var intFlagTests = []struct {
 	name     string
 	expected string

zz_generated.flags.go

@@ -270,6 +270,8 @@ type StringSliceFlag struct {
 	TakesFile bool
 
 	Action func(*Context, []string) error
+
+	NoTrimSpace bool
 }
 
 // IsSet returns whether or not the flag has been set through env or file