avoid-late-keyword

added in: 1.6.0

warning

⚙️🛠

Warns when a field or variable is declared with a late keyword.

late keyword enforces a variable's constraints at runtime instead of at compile time and since the variable is not definitely initialized, every time it is read, a runtime check is inserted to make sure it has been assigned a value. If it hasn’t, an exception will be thrown.

note

Use this rule if you want to avoid unexpected runtime exceptions.

⚙️ Config

Set allow-initialized (default is false) to allow initialized late variable declarations.

Set ignored-types (default is [AnimationController]) to allow some variables of the given type to be declared with late.

dart_code_metrics:
  ...
  rules:
    ...
    - avoid-late-keyword:
        allow-initialized: true

Example

❌ Bad:

class Test {
  late final field = 'string'; // LINT

  final String anotherField = '';

  String? nullableField;

  late String uninitializedField; // LINT

  void method() {
    late final variable = 'string'; // LINT

    final anotherVariable = '';

    String? nullableVariable;

    late String uninitializedVariable; // LINT
  }
}

✅ Good:

class Test {
  final field = 'string';

  final String anotherField = '';

  String? nullableField;

  String uninitializedField;

  void method() {
    final variable = 'string';

    final anotherVariable = '';

    String? nullableVariable;

    String uninitializedVariable;
  }
}