avoid-duplicate-collection-elements

added in: 1.13.0

warning

⚙️

Warns when a collection has duplicate collection elements.

⚙️ Config

Set ignore-literals (default is false) to exclude literals.

dart_code_metrics:
  ...
  rules:
    ...
    - avoid-duplicate-collection-elements:
        ignore-literals: true

Example

❌ Bad:

void fn() {
  final list = <String>[...];

  final anotherList = [
    ...list,
    ...list, // LINT
    if (list.isNotEmpty) 'value',
    if (list.isNotEmpty) 'value', // LINT
  ];

  final map = {
    ...{
      'key': 'value', // LINT
    },
    ...{
      'key': 'value', // LINT
    },
  };
}

✅ Good:

void fn() {
  final list = <String>[...];

  final anotherList = [
    ...list,
    if (list.isNotEmpty) 'value',
  ];

  final map = {
    ...{
      'key': 'value',
    },
  };
}