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False positive for "Style/HashSyntax" when using a variable as a hash key #10401

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mehanoid opened this issue Feb 5, 2022 · 4 comments · Fixed by #10402
Closed

False positive for "Style/HashSyntax" when using a variable as a hash key #10401

mehanoid opened this issue Feb 5, 2022 · 4 comments · Fixed by #10402
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@mehanoid
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mehanoid commented Feb 5, 2022

If you use the same variable as both a hash key and its value, then ruboсop wants to omit the value. The proposed autocorrection breaks the semantics of the code.

Expected behavior

No offences for the following code:

# frozen_string_literal: true

var = 1
{ var => var } # resulting in { 1 => 1}

Actual behavior

For /home/meh/Projects/rubocop-test: Default configuration from /home/meh/.rbenv/versions/3.1.0/lib/ruby/gems/3.1.0/bundler/gems/rubocop-8ae9e0f2081d/config/default.yml
Inspecting 1 file
Scanning /home/meh/Projects/rubocop-test/hash.rb
Loading cache from /home/meh/.cache/rubocop_cache/da7c0adf3cdca36c6db455c7f909e01abe58503a/0536d18c9eb040c724be8df71fd74a67730b58ef/027b8e17147ee3c7f4fce30a50ffb44ff511b6cb
C

Offenses:

hash.rb:4:10: C: [Corrected] Style/HashSyntax: Omit the hash value.
{ var => var }
         ^^^

1 file inspected, 1 offense detected, 1 offense corrected
Finished in 0.18334346099800314 seconds

The code after autocorrection:

# frozen_string_literal: true

var = 1
{ var: } # resulting in { var: 1}

Steps to reproduce the problem

See above

RuboCop version

❯ rubocop -V
1.25.1 (using Parser 3.1.0.0, rubocop-ast 1.15.1, running on ruby 3.1.0 x86_64-linux)
@koic
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koic commented Feb 5, 2022

This is not a false positive because it is an expected behavior of EnforcedShorthandSyntax: always with Ruby 3.1. If you would not like to omit the hash value, please set EnforcedShorthandSyntax: never or EnforcedShorthandSyntax: either.
https://docs.rubocop.org/rubocop/1.25/cops_style.html#enforcedshorthandsyntax-always-default

@koic koic closed this as completed Feb 5, 2022
@mehanoid
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mehanoid commented Feb 5, 2022

@koic hash value omission is only possible when key is a Symbol, otherwise it just breaks the code like in the example above.

@mehanoid
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mehanoid commented Feb 5, 2022

I've updated the examples with comments reflecting the result of running the code

@koic
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koic commented Feb 5, 2022

Ah, you are right. It's my oversight.

@koic koic reopened this Feb 5, 2022
@koic koic added the bug label Feb 5, 2022
koic added a commit to koic/rubocop that referenced this issue Feb 5, 2022
Fixes rubocop#10401.

This PR fixes a false positive for `Style/HashSyntax`
when local variable hash key and hash value are the same.
koic added a commit that referenced this issue Feb 5, 2022
…sh_syntax

[Fix #10401] Fix a false positive for `Style/HashSyntax`
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