MemoizedInstanceVariableName Still complaining about leading underscores

[luke-hill]

Expected behavior

Not to report the cop (not present pre 0.58), fixed in 0.58.0

Actual behavior

rubocop 0.57.2 - 1 file inspected 0 failures
rubocop 0.58.2 - 1 file inspected 1 failure
rubocop 0.59.2 - 1 file inspected 1 failure

Steps to reproduce the problem

# This is fine
def foo
  @foo ||= :foo
end

# This isn't fine
def _foo
  @_foo ||= :foo
end

features/support/cop_test.rb:6:3: C: Naming/MemoizedInstanceVariableName: Memoized variable @_foo does not match method name _foo. Use @_foo instead.

RuboCop version('s)

0.57.2 (using Parser 2.5.1.2, running on ruby 2.2.10 x86_64-linux)
0.58.2 (using Parser 2.5.1.2, running on ruby 2.2.10 x86_64-linux)
0.59.2 (using Parser 2.5.1.2, running on ruby 2.2.10 x86_64-linux)

[luke-hill]

Linked items #6095 #6125

[mikegee]

The default configuration disallows leading underscores: https://rubocop.readthedocs.io/en/latest/cops_naming/#namingmemoizedinstancevariablename

It seems like you want: EnforcedStyleForLeadingUnderscores :optional

[luke-hill]

Hi there @Drenmi think this was closed prematurely.

Those documents don't actual stipulate that my method is against rubocop's guidelines. just that other methods are valid. There isn't an instance where def _foo is given as a bad input.

Furthermore the error message is actual misleading. Because it's advising me to do something I've already done. To rename my method which was previously named _foo to _foo, which is obviously impossible...?

Could someone perhaps shed more light on this, unless I'm missing something obvious this is a legitimate bug.

[matthewrudy]

I think the problem is the error message

$ cat new.rb
# frozen_string_literal: true

def _foo
  @_foo ||= calculate_expensive_thing
end

$ rubocop --version
0.59.2

$ rubocop new.rb
Inspecting 1 file
C

Offenses:

new.rb:4:3: C: Naming/MemoizedInstanceVariableName:
Memoized variable @_foo does not match method name _foo.
Use @_foo instead.

  @_foo ||= calculate_expensive_thing
  ^^^^^

1 file inspected, 1 offense detected

The error message should be

Memoized variable @_foo does not match method name _foo. Use @foo instead.

(or maybe something that explains the bit about the underscoring)

[luke-hill]

Can this be re-opened. As it's still locking us to rubocop 0.57.2 which is quite far behind.

cc/ @Drenmi / @mikegee

[luke-hill]

Could someone maybe point me in the right direction here? As it's a reasonably large open source gem I'm running and this is the only dependency which is quite old.

[matthewrudy]

@luke-hill if you don't agree with it, maybe just turn off this cop.

# .rubocop.yml

Naming/MemoizedInstanceVariableName:
  Enabled: false

[mikegee]

Could someone maybe point me in the right direction here?

Sure! Try removing this pending and try to make it pass.

[luke-hill]

Right so it's actually something being worked on currently. That makes sense then.

[mikegee]

I’m not sure anyone is currently working on it. You might be the most motivated for this particular task.