falcon

Rules / Style / avoid-late-keyword

avoid-late-keyword

lint/style/avoid-late-keyword
recommended
Same as avoid-late-keyword · Dart Code Metrics

Flags use of the late keyword on variables and fields.

late defers initialization and moves the "is it set?" check from compile time to runtime: reading a late variable before it is assigned throws a LateInitializationError rather than failing to compile. Preferring eagerly initialized or nullable declarations keeps that guarantee static and the failure mode visible. Top-level variables, instance fields, and local declarations inside any function body are all checked.

Invalid

example.dartdart
// Test cases for avoid-late-keyword rule
// All lines with violations have the expect annotation at end of line.

class TestClass {
  late int counter;
  late String name;
  late List<String> items;
  late bool isActive;
}

void initializeWithLate() {
  late final String message = "hello";
  late var dynamicValue;
}

class Widget {
  late BuildContext context;

  void setup(BuildContext ctx) {
    context = ctx;
  }
}

mixin StateManagement {
  late final controller = Controller();
}

late int topLevel = 0;
Avoid using the late keyword — use nullable types or initialize immediately instead
4class TestClass {
5 late int counter;
Avoid using the late keyword — use nullable types or initialize immediately instead
5 late int counter;
6 late String name;
Avoid using the late keyword — use nullable types or initialize immediately instead
6 late String name;
7 late List<String> items;
Avoid using the late keyword — use nullable types or initialize immediately instead
7 late List<String> items;
8 late bool isActive;
Avoid using the late keyword — use nullable types or initialize immediately instead
11void initializeWithLate() {
12 late final String message = "hello";
Avoid using the late keyword — use nullable types or initialize immediately instead
12 late final String message = "hello";
13 late var dynamicValue;
Avoid using the late keyword — use nullable types or initialize immediately instead
16class Widget {
17 late BuildContext context;
Avoid using the late keyword — use nullable types or initialize immediately instead
24mixin StateManagement {
25 late final controller = Controller();
Avoid using the late keyword — use nullable types or initialize immediately instead
27
28late int topLevel = 0;

Valid

example.dartdart
// Good cases for avoid-late-keyword rule
// No violations expected

class TestClass {
  int? counter;
  String name = '';
  List<String> items = [];
  bool isActive = false;
}

void initializeWithDefaults() {
  final String message = "hello";
  final dynamicValue = null;
}

class Widget {
  BuildContext? context;

  void setup(BuildContext ctx) {
    context = ctx;
  }
}

mixin StateManagement {
  final controller = Controller();
}

int topLevel = 0;

class DelayedInit {
  String? _delayedValue;

  void initialize() {
    _delayedValue = "initialized";
  }

  String getValue() => _delayedValue ?? '';
}

class OptionalField {
  final int? maybeValue;

  OptionalField(this.maybeValue);
}

How to configure

Set the severity of avoid-late-keyword in your falcon.json:

falcon.jsonjson
{
  "linter": {
    "rules": {
      "style": {
        "avoid-late-keyword": "error"
      }
    }
  }
}

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