falcon

Rules / Complexity / avoid-function-literals-in-foreach-calls

avoid-function-literals-in-foreach-calls

lint/complexity/avoid-function-literals-in-foreach-calls
Same as avoid_function_literals_in_foreach_calls · Dart lints

Flags a function literal passed to forEach, e.g. xs.forEach((e) { ... }).

A for-in loop reads more clearly than forEach with a closure, and unlike the closure it can await, break, and continue, and it allocates no per-call function object. The rule fires only for single-parameter function-literal callbacks, so Map.forEach (which takes two parameters) is left alone, as are tear-offs like xs.forEach(print) and null-aware xs?.forEach(...).

Invalid

example.dartdart
void bad() {
  items.forEach((e) { print(e); });
  list.forEach((x) => print(x));
  names.forEach((name) { save(name); });
  values.forEach((v) => sink(v));
  data.forEach((item) { process(item); log(item); });
}
Avoid using a function literal in a 'forEach' call; use a for-in loop instead.
1void bad() {
2 items.forEach((e) { print(e); });
Avoid using a function literal in a 'forEach' call; use a for-in loop instead.
2 items.forEach((e) { print(e); });
3 list.forEach((x) => print(x));
Avoid using a function literal in a 'forEach' call; use a for-in loop instead.
3 list.forEach((x) => print(x));
4 names.forEach((name) { save(name); });
Avoid using a function literal in a 'forEach' call; use a for-in loop instead.
4 names.forEach((name) { save(name); });
5 values.forEach((v) => sink(v));
Avoid using a function literal in a 'forEach' call; use a for-in loop instead.
5 values.forEach((v) => sink(v));
6 data.forEach((item) { process(item); log(item); });

Valid

example.dartdart
void good() {
  items.forEach(print);
  list?.forEach((e) => print(e));
  map.forEach((k, v) => print('$k$v'));
  for (final e in items) {
    print(e);
  }
  numbers.map((e) => e * 2);
}

How to configure

Set the severity of avoid-function-literals-in-foreach-calls in your falcon.json:

falcon.jsonjson
{
  "linter": {
    "rules": {
      "complexity": {
        "avoid-function-literals-in-foreach-calls": "error"
      }
    }
  }
}

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