proposal: `avoid_sleep`

Description

AVOID calling sleep function from dart:io.

The function should be used with care, as no asynchronous operations can be processed in a isolate while it is blocked in a sleep call.

Kind

Guard against surprised program execution where developer gets confused why no async events are being executed while sleeping.

Bad Examples

import 'dart:io';

void main() {
  sleep(const Duration(seconds: 5));
}

Good Examples

import 'dart:io';

void main() async {
  await Future<void>.delayed(const Duration(seconds: 5));
}

Discussion

I have seen recently, and in the past, a few people getting confused about sleep and misunderstood the consequences of using it (or did not read the documentation). My guess is developers knows the word sleep and thinks that is the way to do sleeping in a function. But then gets surprised when no other code in the isolate gets executed while sleeping.

Most recently example: https://stackoverflow.com/questions/77533267/async-would-not-run-async-in-dart

I do think sleep are very rarely useful and will in most cases be the wrong thing to actually use when the developer wants to insert a delay in code execution.

My suggested lint could be compared to avoid_print which is also about preventing calling a method from the Dart SDK.

Discussion checklist

[ ] List any existing rules this proposal modifies, complements, overlaps or conflicts with.
[ ] List any relevant issues (reported here, the SDK Tracker, or elsewhere).
[ ] If there's any prior art (e.g., in other linters), please add references here.
[ ] If this proposal corresponds to Effective Dart or Flutter Style Guide advice, please call it out. (If there isn't any corresponding advice, should there be?)
[ ] If this proposal is motivated by real-world examples, please provide as many details as you can. Demonstrating potential impact is especially valuable.

dart-lang / linter