prefer_is_empty

The comparison is always 'false' because the length is always greater than or equal to 0.

The comparison is always 'true' because the length is always greater than or equal to 0.

Use 'isEmpty' instead of 'length' to test whether the collection is empty.

Use 'isNotEmpty' instead of 'length' to test whether the collection is empty.

The analyzer produces this diagnostic when the result of invoking either Iterable.length or Map.length is compared for equality with zero (0).

The following code produces this diagnostic because the result of invoking length is checked for equality with zero:

int f(Iterable<int> p) => p.length == 0 ? 0 : p.first;

Replace the use of length with a use of either isEmpty or isNotEmpty:

void f(Iterable<int> p) => p.isEmpty ? 0 : p.first;

Unless stated otherwise, the documentation on this site reflects Dart 3.8.1. Page last updated on 2025-05-08. View source or report an issue.