avoid_duplicate_cascades

v0.4.0 Warning Fix Control Flow

Warns when a cascade expression contains duplicate sections — identical property assignments, method calls, or index operations repeated with the same arguments. Duplicate cascades are usually the result of a copy-paste error.

Why use this rule

When the same cascade section appears twice (e.g., ..name = 'test' repeated), the second one overwrites the first with the same value, making it redundant. For method calls, the duplicate invocation may cause unintended side effects. Either way, it signals a copy-paste mistake that should be fixed.

See also: Cascade notation

Don’t

void bad() {
  // Same property assigned with same value twice
  final config = Config()
    ..name = 'test'
    ..name = 'test';

  // Same method called twice
  final config2 = Config()
    ..reset()
    ..reset();

  // Same index assigned with same value twice
  final list = [1, 2, 3]
    ..[1] = 5
    ..[1] = 5;
}

Do

void good() {
  // Different properties
  final config = Config()
    ..name = 'test'
    ..value = 42;

  // Same property but different values
  final config2 = Config()
    ..name = 'first'
    ..name = 'second';

  // Different indices
  final list = [1, 2, 3]
    ..[0] = 10
    ..[1] = 20;
}

Configuration

This rule is in the core preset, so it is on with preset: core, preset: recommended or preset: opinionated.

To turn it off:

many_lints.yaml

rules:
  avoid_duplicate_cascades: false

To keep the rule on but skip certain paths, use per-rule exclude.

Related rules

• avoid_cascade_after_if_null — Detect cascades after if-null operators without parentheses.
• avoid_collapsible_if — Merge nested if statements with &&.
• avoid_constant_conditions — Detect comparisons where both sides are constants.
• avoid_constant_switches — Detect switch statements on constant expressions.