prefer_spread_collections

Use spread collections when possible.

Use spread collections when possible.

Collection literals are excellent when you want to create a new collection out of individual items. But, when existing items are already stored in another collection, spread collection syntax leads to simpler code.

BAD:

Widget build(BuildContext context) {
  return CupertinoPageScaffold(
    child: ListView(
      children: [
        Tab2Header(),
      ]..addAll(buildTab2Conversation()),
    ),
  );
}

var ints = [1, 2, 3];
print(['a']..addAll(ints.map((i) => i.toString()))..addAll(['c']));

var things;
var l = ['a']..addAll(things ?? const []);

GOOD:

Widget build(BuildContext context) {
  return CupertinoPageScaffold(
    child: ListView(
      children: [
        Tab2Header(),
        ...buildTab2Conversation(),
      ],
    ),
  );
}

var ints = [1, 2, 3];
print(['a', ...ints.map((i) => i.toString()), 'c');

var things;
var l = ['a', ...?things];

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

linter:
  rules:
    - prefer_spread_collections

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

linter:
  rules:
    prefer_spread_collections: true