Fix:(issue_1272) Generic flag not set from env (#1458)

Author: dearchap

flag_bool.go

@@ -51,8 +51,13 @@ 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

@@ -50,7 +50,7 @@ func (f *GenericFlag) GetEnvVars() []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

@@ -169,6 +169,10 @@ 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
 			},
 		}

godoc-current.txt

@@ -5,24 +5,24 @@ line Go applications. cli is designed to be easy to understand and write,
 the most simple cli application can be written as follows:
 
     func main() {
-      (&cli.App{}).Run(os.Args)
+    	(&cli.App{}).Run(os.Args)
     }
 
 Of course this application does not do much, so let's make this an actual
 application:
 
-      func main() {
-        app := &cli.App{
-    			 Name: "greet",
-    			 Usage: "say a greeting",
-    			 Action: func(c *cli.Context) error {
-    				 fmt.Println("Greetings")
-    				 return nil
-    			 },
-    		 }
-
-        app.Run(os.Args)
-      }
+    func main() {
+    	app := &cli.App{
+      		Name: "greet",
+      		Usage: "say a greeting",
+      		Action: func(c *cli.Context) error {
+      			fmt.Println("Greetings")
+      			return nil
+      		},
+    	}
+
+    	app.Run(os.Args)
+    }
 
 VARIABLES
 
@@ -1073,7 +1073,7 @@ type GenericFlag struct {
 }
     GenericFlag is a flag with type Generic
 
-func (f GenericFlag) Apply(set *flag.FlagSet) error
+func (f *GenericFlag) Apply(set *flag.FlagSet) error
     Apply takes the flagset and calls Set on the generic flag with the value
     provided by the user for parsing by the flag