Add FlatMapValidation to Validation type

Signed-off-by: Guillaume Lours <[email protected]>

Author: glours

api/control/validation.go2

@@ -58,6 +58,15 @@ func MapErrorValidation[E, T, U any](validation Validation[E, T], mapper func(E)
 	return Valid[U, T]{validation.OrElse(*new(T))}
 }
 
+// FlatMapValidation maps the valid value of a Validation[E, T] to a new Validation with a valid element of type U.
+// the mapper function should take a T value and return a Validation[E, U] value.
+func FlatMapValidation[E, T, U any](validation Validation[E, T], mapper func(T) Validation[E, U]) Validation[E, U] {
+	if validation.IsValid() {
+		return mapper(validation.OrElse(*new(T)))
+	}
+	return Invalid[E, U]{validation.ErrorOrElse(*new(E))}
+}
+
 // Valid is an implementation of Validation with a valid T value.
 type Valid[E, T any] struct {
 	value T

api/control/validation_test.go2

@@ -161,12 +161,12 @@ func TestMapValidation(t *testing.T) {
 	var mapper = func(value int) string {
 		return strconv.Itoa(value)
 	}
-	var mapValid Validation[error, string] = MapValidation[error, int, string](valid, mapper)
+	var mapValid = MapValidation[error, int, string](valid, mapper)
 	if mapValid.OrElse("good") != "10" {
 		t.Errorf("value should be 10")
 	}
 
-	var mapInvalid Validation[error, string] = MapValidation[error, int, string](invalid, mapper)
+	var mapInvalid = MapValidation[error, int, string](invalid, mapper)
 	if mapInvalid.IsValid() {
 		t.Errorf("should be an Invalid Validation")
 	}
@@ -176,13 +176,28 @@ func TestMapErrorValidation(t *testing.T) {
 	var mapper = func(value error) string {
 		return value.Error()
 	}
-	var mapErrorValid Validation[string, int] = MapErrorValidation[error, int, string](valid, mapper)
+	var mapErrorValid = MapErrorValidation[error, int, string](valid, mapper)
 	if mapErrorValid.OrElse(20) != 10 {
 		t.Errorf("value should be 10")
 	}
 
-	var mapInvalid Validation[string, int] = MapErrorValidation[error, int, string](invalid, mapper)
+	var mapInvalid = MapErrorValidation[error, int, string](invalid, mapper)
 	if mapInvalid.IsValid() {
 		t.Errorf("should be an Invalid Validation")
 	}
-}
+}
+
+func TestFlatMapValidation(t *testing.T) {
+	var mapper = func(value int) Validation[error, string] {
+		return ValidOf[error, string](strconv.Itoa(value))
+	}
+	var flatMapValid = FlatMapValidation(valid, mapper)
+	if flatMapValid.OrElse("good") != "10" {
+		t.Errorf("value should be 10")
+	}
+
+	var flatMapInvalid = FlatMapValidation(invalid, mapper)
+	if flatMapInvalid.IsValid() {
+		t.Errorf("should be an Invalid Validation")
+	}
+}