Skip to main content

avoid-duplicate-patterns

added in: 1.5.0
warning
🛠
Dart 3.0+
Pro+
preset: recommended

Warns when a LogicalOrPattern or LogicalAndPattern contains duplicate patterns.

Duplicate patterns are either the result of a typo or are redundant and can be simply removed.

Example​

❌ Bad:

final object = WithField('hello');

// LINT: Avoid duplicate patterns. Try removing the duplicate pattern or replacing it with a different pattern.
if (object case Object() || Object()) {}

// LINT: Avoid duplicate patterns. Try removing the duplicate pattern or replacing it with a different pattern.
if (object case dynamic() && dynamic()) {}

// LINT: Avoid duplicate patterns. Try removing the duplicate pattern or replacing it with a different pattern.
if (object case != null && Object() && != null) {}

// LINT: Avoid duplicate patterns. Try removing the duplicate pattern or replacing it with a different pattern.
if (object case WithField() || AnotherClass() || WithField()) {}

// LINT: Avoid duplicate patterns. Try removing the duplicate pattern or replacing it with a different pattern.
if (object case > 10 || > 10) {}

final value = switch (object) {
  // LINT: Avoid duplicate patterns. Try removing the duplicate pattern or replacing it with a different pattern.
  != null && Object() && != null => 'bad',

  // LINT: Avoid duplicate patterns. Try removing the duplicate pattern or replacing it with a different pattern.
  WithField() || AnotherClass() || WithField() => 'bad',
};

✅ Good:

final object = WithField('hello');

if (object case Object()) {} // Correct, no duplicate patterns
if (object case dynamic()) {}

if (object case != null && Object()) {}

if (object case WithField() || AnotherClass()) {}

if (object case > 10) {}

final value = switch (object) {
  != null && Object() => 'good',
  WithField() || AnotherClass() => 'good',
};

Additional Resources​