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Cop idea: prefer to_set {...} over map {...}.to_set #11339

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vlad-pisanov opened this issue Dec 27, 2022 · 1 comment · Fixed by #11340
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Cop idea: prefer to_set {...} over map {...}.to_set #11339

vlad-pisanov opened this issue Dec 27, 2022 · 1 comment · Fixed by #11340
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feature request

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@vlad-pisanov
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vlad-pisanov commented Dec 27, 2022 •
edited

This new cop would be a twin of Style/MapToHash, but for .to_set:

# bad
list.map { |x| x + 1 }.to_set
list.collect(&:to_s).to_set
# good
list.to_set { |x| x + 1 }
list.to_set(&:to_s)

Performance-wise, both ways appear to be identical (although there may be some additional memory benefit in avoiding the intermediate .map since sets are implemented using hashes internally 🤷‍♂️)
koic added a commit to koic/rubocop that referenced this issue Dec 27, 2022
@koic
Add new Style/MapToSet cop
211aa90 
Fixes rubocop#11339.

This PR adds new `Style/MapToSet` cop

This cop looks for uses of `map.to_set` or `collect.to_set` that could be
written with just `to_set`. It is unsafe, as it can produce false positives
if the receiver is not an `Enumerable`.

```ruby
# bad
something.map { |i| i * 2 }.to_set

# good
something.to_set { |i| i * 2 }

# bad
[1, 2, 3].collect { |i| i.to_s }.to_set

# good
[1, 2, 3].to_set { |i| i.to_s }
```
@koic koic mentioned this issue Dec 27, 2022
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@koic
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koic commented Dec 27, 2022

This idea looks good to me. I've opened #11340.

bbatsov pushed a commit that referenced this issue Dec 28, 2022
@koic @bbatsov
Add new Style/MapToSet cop
742bef3 
Fixes #11339.

This PR adds new `Style/MapToSet` cop

This cop looks for uses of `map.to_set` or `collect.to_set` that could be
written with just `to_set`. It is unsafe, as it can produce false positives
if the receiver is not an `Enumerable`.

```ruby
# bad
something.map { |i| i * 2 }.to_set

# good
something.to_set { |i| i * 2 }

# bad
[1, 2, 3].collect { |i| i.to_s }.to_set

# good
[1, 2, 3].to_set { |i| i.to_s }
```
@koic koic mentioned this issue Jan 13, 2023
Merged
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Add new Style/MapToSet cop koic/rubocop
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@koic @vlad-pisanov