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no-equal-arguments

added in: 1.6.0
warning
⚙️
Pro+

Warns when equal arguments passed to a function or method invocation.

Passing the same argument (for example, a variable) to a function or method invocation more than once is usually a sign of a bug.

⚙️ Config​

Set ignored-parameters (default is empty) to ignore specific named parameters (example).

Set ignored-arguments (default is empty) to ignore specific argument names (example).

Set ignore-inline-functions (default is false) to ignore inline functions that are passed as arguments (example).

analysis_options.yaml
dart_code_metrics:
  rules:
    - no-equal-arguments:
        ignored-parameters:
          - height
          - width
        ignored-arguments:
          - someName
        ignore-inline-functions: false

Example​

❌ Bad:

class User {
  final String firstName;
  final String lastName;

  const User(this.firstName, this.lastName);
}

User createUser(String firstName, String lastName)  {
  return User(
    firstName,
    firstName, // LINT: Target expression already has an argument with the same value. Try checking it for a potential mistake.
  );
}

void getUserData(User user) {
  String getFullName(String firstName, String lastName) {
    return firstName + ' ' + lastName;
  }

  final fullName = getFullName(
    user.firstName,
    user.firstName, // LINT: Target expression already has an argument with the same value. Try checking it for a potential mistake.
  );
}

✅ Good:

class User {
  final String firstName;
  final String lastName;

  const User(this.firstName, this.lastName);
}

User createUser(String firstName, String lastName)  {
  return User(
    firstName,
    lastName,
  );
}

void getUserData(User user) {
  String getFullName(String firstName, String lastName) {
    return firstName + ' ' + lastName;
  }

  final fullName = getFullName(
    user.firstName,
    user.lastName,
  );
}

Example with "ignored-parameters"​

Config
analysis_options.yaml
dart_code_metrics:
  rules:
    - no-equal-arguments:
        ignored-parameters:
          - lastName

✅ Good:

class User {
  final String firstName;
  final String lastName;

  const User({required this.firstName, required this.lastName});
}

User createUser(String firstName, String lastName)  {
  return User(
    firstName: firstName,
    lastName: firstName, // Correct, 'lastName' is ignored
  );
}

Example with "ignored-arguments"​

Config
analysis_options.yaml
dart_code_metrics:
  rules:
    - no-equal-arguments:
        ignored-arguments:
          - firstName

✅ Good:

class User {
  final String firstName;
  final String lastName;

  const User({required this.firstName, required this.lastName});
}

User createUser(String firstName, String lastName)  {
  return User(
    firstName: firstName,
    lastName: firstName, // Correct, 'firstName' is ignored
  );
}

Example with "ignore-inline-functions"​

Config
analysis_options.yaml
dart_code_metrics:
  rules:
    - no-equal-arguments:
        ignore-inline-functions: false

✅ Good:

void main() {
  WithFunctions(
    () => null,
    () => null, // Correct, ignored
  );
}

class WithFunctions {
  final void Function() first;
  final void Function() second;

  const WithFunctions(this.first, this.second);
}

Additional Resources​