avoid-unsafe-collection-methods

added in: 1.4.0

🛠

Pro+

Warns when first, last, single, firstWhere, lastWhere, singleWhere or [] methods are used on Iterable or its subclasses.

Accessing elements via these methods can result in an exception being thrown at runtime, if there are no element found. To avoid that, use firstOrNull, lastOrNull, singleOrNull, firstWhereOrNull, lastWhereOrNull, singleWhereOrNull or elementAtOrNull from the collection package instead.

note

The rule won't trigger on a [] used on a map.

Example

❌ Bad:

List<String> someList = [...];

someList.first; // LINT
someList.last; // LINT
someList.single; // LINT

someList.firstWhere(...); // LINT
someList.lastWhere(...); // LINT
someList.singleWhere(...); // LINT

if (someList case Set(:final first)) {} // LINT
if (someList case Set(first: final f)) {} // LINT

✅ Good:

List<String> someList = [...];

someList.firstOrNull;
someList.lastOrNull;
someList.singleOrNull;

someList.firstWhereOrNull(...);
someList.lastWhereOrNull(...);
someList.singleWhereOrNull(...);

if (someList case Set(:final firstOrNull)) {}
if (someList case Set(firstOrNull: final orNull)) {}

ListView.builder(
  itemCount: nullable?.length ?? 0,
  itemBuilder: (_, index) {
    nullable[index];
  },
);

Example​

Example