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Add warning for IO.select with single argument. #9061

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ioquatix opened this issue Nov 16, 2020 · 2 comments · Fixed by #10075
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Add warning for IO.select with single argument. #9061

ioquatix opened this issue Nov 16, 2020 · 2 comments · Fixed by #10075
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feature request

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@ioquatix
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ioquatix commented Nov 16, 2020 •
edited

Maybe this is a crazy idea, but it would be awesome if we could automatically rewrite the following:

IO.select([io], [], [], timeout)
# becomes
io.wait_readable(timeout)

IO.select([], [io], [], timeout)
# becomes
io.wait_writable(timeout)

And finally, every other usage of IO.select becomes warning/error.

Because it is very hard to make it compatible with Ruby 3 scheduler.

It could be disabled by default if it's too inconvenient.
@ioquatix
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Here is an example PR: redis/redis-rb#960

koic added a commit to koic/rubocop that referenced this issue Sep 11, 2021
@koic
[Fix rubocop#9061] Add new `Lint/IncompatibleIoSelectWithFiberSchedul…
9e09a84 
…er` cop

Fixes rubocop#9061.

This PR adds new `Lint/IncompatibleIoSelectWithFiberScheduler` cop.
It checks for `IO.select` that is incompatible with Fiber Scheduler since Ruby 3.0.

```ruby
# bad
IO.select([io], [], [], timeout)

# good
io.wait_readable(timeout)

# bad
IO.select([], [io], [], timeout)

# good
io.wait_writable(timeout)
```

Ref: `Fiber Scheduler` section of https://www.ruby-lang.org/en/news/2020/12/25/ruby-3-0-0-released/

This PR will make it possible to detect proven cases with redis/redis-rb#960.
@koic koic mentioned this issue Sep 11, 2021
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bbatsov pushed a commit that referenced this issue Sep 12, 2021
@koic @bbatsov
[Fix #9061] Add new Lint/IncompatibleIoSelectWithFiberScheduler cop
f7c21e1 
Fixes #9061.

This PR adds new `Lint/IncompatibleIoSelectWithFiberScheduler` cop.
It checks for `IO.select` that is incompatible with Fiber Scheduler since Ruby 3.0.

```ruby
# bad
IO.select([io], [], [], timeout)

# good
io.wait_readable(timeout)

# bad
IO.select([], [io], [], timeout)

# good
io.wait_writable(timeout)
```

Ref: `Fiber Scheduler` section of https://www.ruby-lang.org/en/news/2020/12/25/ruby-3-0-0-released/

This PR will make it possible to detect proven cases with redis/redis-rb#960.
@ioquatix
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This is amazing thanks!

@smudge smudge mentioned this issue Oct 26, 2021
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[Fix #9061] Add new Lint/IncompatibleIoSelectWithFiberScheduler cop koic/rubocop
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@ioquatix @bbatsov