prefer_asserts_with_message

Prefer asserts with message.

When assertions fail it's not always simple to understand why. Adding a message to the assert helps the developer to understand why the AssertionError occurs.

BAD:

f(a) {
  assert(a != null);
}

class A {
  A(a) : assert(a != null);
}

GOOD:

f(a) {
  assert(a != null, 'a must not be null');
}

class A {
  A(a) : assert(a != null, 'a must not be null');
}

To enable the prefer_asserts_with_message rule, add prefer_asserts_with_message under linter > rules in your analysis_options.yaml file:

linter:
  rules:
    - prefer_asserts_with_message

If you're instead using the YAML map syntax to configure linter rules, add prefer_asserts_with_message: true under linter > rules:

linter:
  rules:
    prefer_asserts_with_message: true

Unless stated otherwise, the documentation on this site reflects Dart 3.6.0. Page last updated on 2025-01-27. View source or report an issue.