fix: ensure pointers can be detected as bools

This required adding a BoolMapperExt interface.

mapper.go

@@ -123,9 +123,16 @@ type VarsContributor interface {
 //
 // This is used solely for formatting help.
 type BoolMapper interface {
+	Mapper
 	IsBool() bool
 }
 
+// BoolMapperExt allows a Mapper to dynamically determine if a value is a boolean.
+type BoolMapperExt interface {
+	Mapper
+	IsBoolFromValue(v reflect.Value) bool
+}
+
 // A MapperFunc is a single function that complies with the Mapper interface.
 type MapperFunc func(ctx *DecodeContext, target reflect.Value) error
 
@@ -186,6 +193,7 @@ func (r *Registry) ForType(typ reflect.Type) Mapper {
 	// Check if the type implements MapperValue.
 	for _, impl := range []reflect.Type{typ, reflect.PtrTo(typ)} {
 		if impl.Implements(mapperValueType) {
+			// FIXME: This should pass in the bool mapper.
 			return &mapperValueAdapter{impl.Implements(boolMapperType)}
 		}
 	}
@@ -275,7 +283,7 @@ func (r *Registry) RegisterDefaults() *Registry {
 		RegisterName("existingfile", existingFileMapper(r)).
 		RegisterName("existingdir", existingDirMapper(r)).
 		RegisterName("counter", counterMapper()).
-		RegisterKind(reflect.Ptr, ptrMapper(r))
+		RegisterKind(reflect.Ptr, ptrMapper{r})
 }
 
 type boolMapper struct{}
@@ -676,10 +684,31 @@ func existingDirMapper(r *Registry) MapperFunc {
 	}
 }
 
-func ptrMapper(r *Registry) MapperFunc {
-	return func(ctx *DecodeContext, target reflect.Value) error {
+type ptrMapper struct {
+	r *Registry
+}
+
+var _ BoolMapperExt = (*ptrMapper)(nil)
+
+// IsBoolFromValue implements BoolMapperExt
+func (p ptrMapper) IsBoolFromValue(target reflect.Value) bool {
 	elem := reflect.New(target.Type().Elem()).Elem()
-		nestedMapper := r.ForValue(elem)
+	nestedMapper := p.r.ForValue(elem)
+	if nestedMapper == nil {
+		return false
+	}
+	if bm, ok := nestedMapper.(BoolMapper); ok && bm.IsBool() {
+		return true
+	}
+	if bm, ok := nestedMapper.(BoolMapperExt); ok && bm.IsBoolFromValue(target) {
+		return true
+	}
+	return target.Kind() == reflect.Ptr && target.Type().Elem().Kind() == reflect.Bool
+}
+
+func (p ptrMapper) Decode(ctx *DecodeContext, target reflect.Value) error {
+	elem := reflect.New(target.Type().Elem()).Elem()
+	nestedMapper := p.r.ForValue(elem)
 	if nestedMapper == nil {
 		return fmt.Errorf("cannot find mapper for %v", target.Type().Elem().String())
 	}
@@ -690,7 +719,6 @@ func ptrMapper(r *Registry) MapperFunc {
 	target.Set(elem.Addr())
 	return nil
 }
-}
 
 func counterMapper() MapperFunc {
 	return func(ctx *DecodeContext, target reflect.Value) error {

model.go

@@ -318,6 +318,9 @@ func (v *Value) IsMap() bool {
 
 // IsBool returns true if the underlying value is a boolean.
 func (v *Value) IsBool() bool {
+	if m, ok := v.Mapper.(BoolMapperExt); ok && m.IsBoolFromValue(v.Target) {
+		return true
+	}
 	if m, ok := v.Mapper.(BoolMapper); ok && m.IsBool() {
 		return true
 	}