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feature_envy

Warns if a method accesses fields or methods from a different class more often than from its own class (feature envy).

Example​

BAD:

class A {
  int field;
  A(this.field);
}

class B {
  int method(A a) => a.field * a.field; // LINT
}

GOOD:

class A {
  int field;
  A(this.field);

  int method() => field * field;
}

class B {
  int method(A a) => a.method();
}

Detection Algorithm​

The rule detects feature envy using three metrics:

  • ATFD (Access to Foreign Data): Accesses to members of a single external class. Triggers if ATFD >= threshold (default 4).
  • LAA (Locality of Attribute Access): The ratio of internal accesses to total accesses. Triggers if LAA < threshold (default 0.33).
  • FDP (Foreign Data Providers): The number of unique external classes accessed. Triggers if FDP <= threshold (default 2).

Accesses to other instances of the same class, non-project classes, closures, nested functions, and data classes are ignored.

Parameters​

exclude (String | Map | List<String | Map>)​

A list of methods that should be excluded from the lint.

atfd_threshold (int)​

Access to Foreign Data (ATFD) threshold. Triggered if ATFD >= atfdThreshold.

laa_threshold (double)​

Locality of Attribute Access (LAA) threshold. Triggered if LAA < laaThreshold.

fdp_threshold (int)​

Foreign Data Providers (FDP) threshold. Triggered only if FDP <= fdpThreshold.