Fix:(issue_1272) Generic flag not set from env

flag_bool.go

@@ -31,8 +31,13 @@ func (f *BoolFlag) Apply(set *flag.FlagSet) error {
 			}
 
 			f.Value = valBool
-			f.HasBeenSet = true
+		} else {
+			// empty value implies that the env is defined but set to empty string, we have to assume that this is
+			// what the user wants. If user doesnt want this then the env needs to be deleted or the flag removed from
+			// file
+			f.Value = false
 		}
+		f.HasBeenSet = true
 	}
 
 	for _, name := range f.Names() {

flag_generic.go

@@ -22,7 +22,7 @@ func (f *GenericFlag) GetValue() string {
 
 // Apply takes the flagset and calls Set on the generic flag with the value
 // provided by the user for parsing by the flag
-func (f GenericFlag) Apply(set *flag.FlagSet) error {
+func (f *GenericFlag) Apply(set *flag.FlagSet) error {
 	if val, source, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
 		if val != "" {
 			if err := f.Value.Set(val); err != nil {

flag_test.go

@@ -166,6 +166,10 @@ func TestFlagsFromEnv(t *testing.T) {
 				if !reflect.DeepEqual(ctx.Value(test.flag.Names()[0]), test.output) {
 					t.Errorf("ex:%01d expected %q to be parsed as %#v, instead was %#v", i, test.input, test.output, ctx.Value(test.flag.Names()[0]))
 				}
+				if !f.IsSet() {
+					t.Errorf("Flag %s not set", f.Names()[0])
+				}
+
 				return nil
 			},
 		}