An error occurred while Style/RescueEnsureAlignment cop was inspecting

[rrosenblum]

The error message is undefined method 'include?' for nil:NilClass. This is happening in version 0.33.0.

I am trying to limit down the code that causes this issue to provide example source. Placing breakpoints in the code, it appears that investigate isn't being run so @modifier_locations is not set.

A quick fix would be

def modifier?(node)
  @modifier_locations.include?(node.loc.keyword) if @modifier_locations
end

or initializing @modifier_locations to [].

One of the safeguards is worthwhile, but I am more curious why investigate does not appear to be running at all.

[lumeet]

Any news on this, @rrosenblum? I haven't been able to reproduce the issue.

[rrosenblum]

I am working on reproducing the issue. I have been unable to boil the code down to a small reproducible state. The error consistently happens on one of my machines, but I can not reproduce it on another.

The issue is that investigate is not being run, before or after on_resbody is being run. One of the fixes listed earlier will fix this issue, but I am unsure why the issue is happening in the first place.

[rrosenblum]

I found the issue, and a way to reproduce it. The issue isn't specifically with Style/RescueEnsureAlignment. It seems to be caused by excluding a file from a specific cop not working properly.

# .rubocop.yml
Style/RescueEnsureAlignment:
  Exclude:               
    - 'test.rb' 

# test.rb
begin
  foo 
rescue
  bar 
end

When RuboCop is run, it will wind up inspecting the code in test.rb even though it is excluded. investigate is not run because of the code in Commissioner#invoke_custom_processing which is why @modifier_locations is nil.

This issue does not happen when the file is excluded from AllCops.

I am going to have to do some digging into how to fix this issue.

Looping in @bbatsov and @jonas054.

[rrosenblum]

It appears that the way Excluded files are handled is that the cop runs all on_ handlers in that file and then the offenses for that cop are ignored. invoke_custom_processing will skip running the investigate method on the file.

From the commissioner code

  def investigate(processed_source)
    reset_errors
    prepare(processed_source)
    invoke_custom_processing(@cops, processed_source)
    invoke_custom_processing(@forces, processed_source)
    process(processed_source.ast) if processed_source.ast
    @cops.each_with_object([]) do |cop, offenses|
      filename = processed_source.buffer.name
      # ignore files that are of no interest to the cop in question
      offenses.concat(cop.offenses) if cop.relevant_file?(filename)
    end
  end

This doesn't seem like the best way to handle this. It would be preferable if we could avoid running the on_ handlers in these cops all together. I will continue researching, but as of right now, I can not think of a way to implement this.

I will add a bug fix for undefined method 'include?' and continue researching a more thorough solution.