Reworking value source API

command_test.go

@@ -51,7 +51,7 @@ func buildExtendedTestCommand() *Command {
 			Name:    "another-flag",
 			Aliases: []string{"b"},
 			Usage:   "another usage text",
-			Sources: ValueSources{EnvSource("EXAMPLE_VARIABLE_NAME")},
+			Sources: EnvVars("EXAMPLE_VARIABLE_NAME"),
 		},
 		&BoolFlag{
 			Name:   "hidden-flag",

flag_bool_with_inverse.go

@@ -89,7 +89,7 @@ func (parent *BoolWithInverseFlag) initialize() {
 	parent.negativeFlag = &BoolFlag{
 		Category:    child.Category,
 		DefaultText: child.DefaultText,
-		Sources:     append(ValueSources{}, child.Sources...),
+		Sources:     ValueSourceChain{Chain: append([]ValueSource{}, child.Sources.Chain...)},
 		Usage:       child.Usage,
 		Required:    child.Required,
 		Hidden:      child.Hidden,
@@ -108,10 +108,11 @@ func (parent *BoolWithInverseFlag) initialize() {
 	parent.negativeFlag.Name = parent.inverseName()
 	parent.negativeFlag.Aliases = parent.inverseAliases()
 
-	if len(child.Sources) > 0 {
-		parent.negativeFlag.Sources = make(ValueSources, len(child.Sources))
+	if len(child.Sources.Chain) > 0 {
+		parent.negativeFlag.Sources = ValueSourceChain{Chain: make([]ValueSource, len(child.Sources.Chain))}
+
 		for idx, envVar := range child.GetEnvVars() {
-			parent.negativeFlag.Sources[idx] = EnvSource(strings.ToUpper(parent.InversePrefix) + envVar)
+			parent.negativeFlag.Sources.Chain[idx] = &envVarValueSource{Key: strings.ToUpper(parent.InversePrefix) + envVar}
 		}
 	}
 }

flag_bool_with_inverse_test.go

@@ -199,7 +199,7 @@ func TestBoolWithInverseEnvVars(t *testing.T) {
 		return &BoolWithInverseFlag{
 			BoolFlag: &BoolFlag{
 				Name:    "env",
-				Sources: ValueSources{EnvSource("ENV")},
+				Sources: EnvVars("ENV"),
 			},
 		}
 	}

flag_impl.go

@@ -86,7 +86,7 @@ type FlagBase[T any, C any, VC ValueCreator[T, C]] struct {
 	DefaultText string // default text of the flag for usage purposes
 	Usage       string // usage string for help output
 
-	Sources ValueSources // sources to load flag value from
+	Sources ValueSourceChain // sources to load flag value from
 
 	Required   bool // whether the flag is required or not
 	Hidden     bool // whether to hide the flag in help output
@@ -132,16 +132,22 @@ func (f *FlagBase[T, C, V]) Apply(set *flag.FlagSet) error {
 	if !f.applied || !f.Persistent {
 		newVal := f.Value
 
-		if val, source, found := f.Sources.Get(); found {
+		if val, source, found := f.Sources.LookupWithSource(); found {
 			tmpVal := f.creator.Create(f.Value, new(T), f.Config)
 			if val != "" || reflect.TypeOf(f.Value).Kind() == reflect.String {
 				if err := tmpVal.Set(val); err != nil {
-					return fmt.Errorf("could not parse %q as %T value from %s for flag %s: %s", val, f.Value, source, f.Name, err)
+					return fmt.Errorf(
+						"could not parse %[1]q as %[2]T value from %[3]s for flag %[4]s: %[5]s",
+						val, f.Value, source, f.Name, err,
+					)
 				}
 			} else if val == "" && reflect.TypeOf(f.Value).Kind() == reflect.Bool {
 				val = "false"
 				if err := tmpVal.Set(val); err != nil {
-					return fmt.Errorf("could not parse %q as %T value from %s for flag %s: %s", val, f.Value, source, f.Name, err)
+					return fmt.Errorf(
+						"could not parse %[1]q as %[2]T value from %[3]s for flag %[4]s: %[5]s",
+						val, f.Value, source, f.Name, err,
+					)
 				}
 			}
 
@@ -206,13 +212,15 @@ func (f *FlagBase[T, C, V]) GetUsage() string {
 
 // GetEnvVars returns the env vars for this flag
 func (f *FlagBase[T, C, V]) GetEnvVars() []string {
-	var envs []string
-	for _, src := range f.Sources {
-		if esrc, ok := src.(EnvSource); ok {
-			envs = append(envs, string(esrc))
+	vals := []string{}
+
+	for _, src := range f.Sources.Chain {
+		if v, ok := src.(*envVarValueSource); ok {
+			vals = append(vals, v.Key)
 		}
 	}
-	return envs
+
+	return vals
 }
 
 // TakesValue returns true if the flag takes a value, otherwise false