add Usage to the api

Author: ldemailly

dyngeneric.go

@@ -89,6 +89,7 @@ type DynValue[T any] struct {
 	notifier     func(oldValue T, newValue T)
 	mutator      func(inp T) T
 	inpMutator   func(inp string) string
+	usage        string
 }
 
 func Dyn[T DynValueTypes](flagSet *flag.FlagSet, name string, value T, usage string) *DynValue[T] {
@@ -104,6 +105,7 @@ func dynInit[T any](dynValue *DynValue[T], flagSet *flag.FlagSet, name string, v
 	dynValue.flagSet = flagSet
 	dynValue.av.Store(value)
 	dynValue.inpMutator = strings.TrimSpace // default so parsing of numbers etc works well
+	dynValue.usage = usage
 	dynValue.ready = true
 }
 
@@ -134,6 +136,11 @@ func (d *DynValue[T]) Get() T {
 	return d.av.Load().(T)
 }
 
+// Usage returns the usage string for the flag.
+func (d *DynValue[T]) Usage() string {
+	return d.usage
+}
+
 // CommaStringToSlice converts a coma separated string to a slice.
 func CommaStringToSlice(input string) []string {
 	// originally the heavy handed csv.NewReader(strings.NewReader(input)).Read()

dynstring_test.go

@@ -17,6 +17,7 @@ const notifierTimeout = 100 * time.Millisecond
 func TestDynString_SetAndGet(t *testing.T) {
 	set := flag.NewFlagSet("foobar", flag.ContinueOnError)
 	dynFlag := DynString(set, "some_string_1", "something", "Use it or lose it")
+	assert.Equal(t, "Use it or lose it", dynFlag.Usage(), "Usage() should be what was passed in")
 	assert.Equal(t, "something", dynFlag.Get(), "value must be default after create")
 	err := set.Set("some_string_1", "else")
 	assert.NoError(t, err, "setting value must succeed")