validasi_gen (experimental)

Experimental — API subject to change. Feedback and contributions are welcome!

Code generator for Validasi. Turns @ValidateClass() and @Validate(...) annotations on a Dart model into a typed XFields<V> hierarchy, a validate() / validateAsync() extension, and (optionally) a form-aware validateForm_X(ctrl).

Quick start

pubspec.yaml:

dependencies:
  validasi: ^1.0.0-rc.1
  validasi_annotation: ^0.1.0-dev.2

dev_dependencies:
  build_runner: ^2.4.0
  validasi_gen: ^0.1.0-dev.2

Source model:

import 'package:validasi/validasi.dart';
import 'package:validasi_annotation/validasi_annotation.dart';

part 'user.g.dart';

@ValidateClass()
class User {
  @Validate.string([MinLength(3), MaxLength(100)])
  final String email;

  const User({required this.email});
}

Run the generator:

dart run build_runner build

You now have UserFields<V>, UserNameField, UserEmailField, and an extension $UserValidasi on User with validate() / validateAsync() / validateField().

What you get

For every class annotated with @ValidateClass, the generator emits (into *.g.dart as a part of file):

Artifact When Purpose
sealed class XFields<V> extends ValidasiKey<X> implements ValidasiField<X, V> always The type-safe field key hierarchy.
static const XFields<V> fieldName = XFieldNameField(); per field Singletons for every annotated field.
class XFieldNameField extends XFields<String> per field Leaf that runs the field's rules.
extension $XValidasi on X { validate(), validateAsync() } always Whole-object validation.
extension $XValidasi on X { validateField<V>(field), validateFieldAsync<V>(field) } when generateFields: true Per-field validation using a XFields<V> key.
X assemble_X(ValidasiFormController<X> ctrl) when generateAssemble: true Materialise a X from a form controller.
ValidasiResult<X> validateForm_X(ValidasiFormController<X> ctrl) when generateValidateForm: true Form-aware validation that reads per-field values and runs refines.

Build options

Set in the downstream package's build.yaml:

targets:
  $default:
    builders:
      validasi_gen:validasi:
        options:
          generateFields: true
          generateAssemble: true
          generateValidateForm: false
Option Default What it controls
generateFields true Emit XFields sealed hierarchy + validateField() on the extension.
generateAssemble true Emit X assemble_X(ValidasiFormController<X> ctrl).
generateValidateForm false Emit ValidasiResult<X> validateForm_X(ValidasiFormController<X> ctrl).

generateValidateForm is off by default because the emitted function references ValidasiFormController, which lives in the Flutter-dependent validasi_ui package. Flutter consumers opt in by setting it to true and importing validasi_ui in the source file. Pure-Dart packages leave it off.

Per-class overrides always win:

@ValidateClass(generateFields: false, generateAssemble: false)
class Internal { ... }

Refine (cross-field validation)

For object- or form-level rules that span multiple fields, mark a method with @RefineFn(dependsOn: [...]). The method receives a FailFn as its first positional argument and named parameters matching the field names in dependsOn:

class User {
  final String email;
  final String confirmEmail;

  @RefineFn(dependsOn: ['email', 'confirmEmail'])
  void emailsMatch(
    FailFn fail, {
    String? email,
    String? confirmEmail,
  }) {
    if (email != null && confirmEmail != null && email != confirmEmail) {
      fail(message: 'Emails do not match', path: ['confirmEmail']);
    }
  }
}

The generator wires the method into both validate() (using this) and validateForm_X(ctrl) (using ctrl.getValue(...)). Return Future<void> for async refines — the generator detects it and inserts await.

See also

  • ARCH.md — full pipeline walkthrough, file-by-file map, and extension guide.
  • packages/validasi_annotation — the annotation surface (@ValidateClass, @Validate, @RefineFn, built-in rules, FailFn).
  • packages/validasi — the runtime engine (ValidasiResult, ValidationError, ValidationState).
  • packages/validasi_ui — the Flutter-side form controller that consumes the generated validateForm_X(ctrl).

Libraries

validasi_gen