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avoid-unused-parameters

added in: 1.6.0
warning
⚙️🛠
Pro+
preset: recommended

Checks for unused parameters inside a function or method body.

For overridden methods suggests renaming unused parameters to _, __, etc.

info

Abstract classes are completely ignored by the rule to avoid redundant checks for potentially overridden methods.

⚙️ Config​

Set ignore-inline-functions (default is true) to ignore inline functions (example). Default value is set to true for backward compatibility and can be changed in the future.

analysis_options.yaml
dart_code_metrics:
  rules:
    - avoid-unused-parameters:
        ignore-inline-functions: true

Example​

❌ Bad:

void someFunction(String s) { // LINT: Parameter is not used. Try removing it, renaming to _ or referencing it in code.
  return;
}

class SomeClass {
  void method(String s) { // LINT: Parameter is not used. Try removing it, renaming to _ or referencing it in code.
    return;
  }
}

class SomeClass extends AnotherClass {
  @override
  void method(String s) {} // LINT: Parameter is not used. Try removing it, renaming to _ or referencing it in code.
}

✅ Good:

void someOtherFunction() {
  return;
}

class SomeOtherClass {
  void method() {
    return;
  }
}

void someOtherFunction(String s) {
  print(s);
  return;
}

class SomeOtherClass {
  void method(String s) {
    print(s);
    return;
  }
}

class SomeOtherClass extends AnotherClass {
  @override
  void method(String _) {}
}

abstract class SomeOtherClass {
  void method(String s);
}

Example with "ignore-inline-functions"​

Config
analysis_options.yaml
dart_code_metrics:
  rules:
    - avoid-unused-parameters:
        ignore-inline-functions: false

❌ Bad:

class TestClass {
  void _someNamedCallback({required Function(String, int) callback}) {
    callback();
  }

  void _anotherMethod() {
    // LINT: Parameter is not used. Try removing it, renaming to _ or referencing it in code.
    _someNamedCallback(callback: (value, counter) {
      print(value);
    });
  }
}

Additional Resources​