Fix:(issue_1263) FlagNames should return names set via env as well

context.go

@@ -82,15 +82,35 @@ func (cCtx *Context) IsSet(name string) bool {
 func (cCtx *Context) LocalFlagNames() []string {
 	var names []string
 	cCtx.flagSet.Visit(makeFlagNameVisitor(&names))
-	return names
+	// Check the flags which have been set via env or file
+	if cCtx.Command != nil && cCtx.Command.Flags != nil {
+		for _, f := range cCtx.Command.Flags {
+			if f.IsSet() {
+				names = append(names, f.Names()...)
+			}
+		}
+	}
+
+	// Sort out the duplicates since flag could be set via multiple
+	// paths
+	m := map[string]struct{}{}
+	var unames []string
+	for _, name := range names {
+		if _, ok := m[name]; !ok {
+			m[name] = struct{}{}
+			unames = append(unames, name)
+		}
+	}
+
+	return unames
 }
 
 // FlagNames returns a slice of flag names used by the this context and all of
 // its parent contexts.
 func (cCtx *Context) FlagNames() []string {
 	var names []string
 	for _, pCtx := range cCtx.Lineage() {
-		pCtx.flagSet.Visit(makeFlagNameVisitor(&names))
+		names = append(names, pCtx.LocalFlagNames()...)
 	}
 	return names
 }

flag_test.go

@@ -239,6 +239,10 @@ func TestFlagsFromEnv(t *testing.T) {
 					t.Errorf("Flag %s not set", f.Names()[0])
 				}
 
+				// check that flag names are returned when set via env as well
+				if !reflect.DeepEqual(ctx.FlagNames(), test.flag.Names()) {
+					t.Errorf("Not enough flag names %+v", ctx.FlagNames())
+				}
 				return nil
 			},
 		}

sliceflag_test.go

@@ -156,8 +156,8 @@ func ExampleMultiStringFlag() {
 	//---
 	//Setting all flags via environment...
 	//
-	//Flag names: []
-	//Local flag names: []
+	//Flag names: ["flag-one" "1" "two" "2" "flag-three" "3" "flag-four" "4"]
+	//Local flag names: ["flag-one" "1" "two" "2" "flag-three" "3" "flag-four" "4"]
 	//Context values:
 	//"flag-one"=["v 9" "v 10"]
 	//"two"=["v 11" "v 12"]