exhaustive_cases

Define case clauses for all constants in enum-like types.

Switching on instances of enum-like types should cover all known constants.

Enum-like types are classes or extension types that have:

• only private non-factory constructors
• two or more static const fields whose type is the enclosing type

In addition, enum-like classes are concrete (non-abstract) and have no subclasses in the defining library.

DO define case clauses for all constants in enum-like types.

Extension types can also be enum-like:

extension type const E._(int value) {
  static const E a = E._(1);
  static const E b = E._(2);
}
​
void f(E e) {
  switch (e) { // LINT
    case E.a:
      print('a');
  }
}

BAD:

class EnumLike {
  final int i;
  const EnumLike._(this.i);
​
  static const e = EnumLike._(1);
  static const f = EnumLike._(2);
  static const g = EnumLike._(3);
}
​
void bad(EnumLike e) {
  // Missing case.
  switch(e) { // LINT
    case EnumLike.e :
      print('e');
      break;
    case EnumLike.f :
      print('f');
      break;
  }
}

GOOD:

class EnumLike {
  final int i;
  const EnumLike._(this.i);
​
  static const e = EnumLike._(1);
  static const f = EnumLike._(2);
  static const g = EnumLike._(3);
}
​
void ok(EnumLike e) {
  // All cases covered.
  switch(e) { // OK
    case EnumLike.e :
      print('e');
      break;
    case EnumLike.f :
      print('f');
      break;
    case EnumLike.g :
      print('g');
      break;
  }
}

To enable the exhaustive_cases rule, add exhaustive_cases under linter > rules in your analysis_options.yaml file:

linter:
  rules:
    - exhaustive_cases

If you're instead using the YAML map syntax to configure linter rules, add exhaustive_cases: true under linter > rules:

linter:
  rules:
    exhaustive_cases: true