Generate `# credo:disable*` comments and find unneeded ones

[dmarcoux]

Hi,

I'm introducing Credo in a fairly large project. As a starting point to get us going, I ignore a lot of Credo issues with one of the inline config comments. I generated those with the help of Claude Code. It's somewhat slow, but it works well most of the time. It did happen though that some of the comments it generated were wrong. I had to manually review a lot of files to ensure no comment is superfluous.

So with this in mind, it got me thinking. Would it be possible for Credo to generate those # credo:disable* comments?

I worked a lot with Ruby and this reminds me of RuboCop, a linter for Ruby. It has this feature where you generate the RuboCop configuration and it automatically ignores all offenses it finds. This is a great developer experience and it's super easy to get started this way. Here's a quote from RuboCop's docs on that feature:

If you have a code base with an overwhelming amount of offenses, it can be a good idea to use rubocop --auto-gen-config, which creates .rubocop_todo.yml and adds inherit_from: .rubocop_todo.yml in your .rubocop.yml. The generated file .rubocop_todo.yml contains configuration to disable cops that currently detect an offense in the code by changing the configuration for the cop, excluding the offending files, or disabling the cop altogether once a file count limit has been reached.

As for finding unneeded # credo:disable* comments, I have to make another parallel to RuboCop... sorry I worked in Ruby for many years. It has this nice check where it detects unneeded disable comments. Is this possible in Credo? I haven't found something about this.

Sorry for the wall of text, let me know if I wasn't clear.

Thank you for your work on Credo.

[rrrene]

This is definitely a valid use case.

Not sure that generating the comments is the best way to go.

But we can already exclude checks for specific files in Credo, which seems close to what Rubocop does.

WDYT?

[dmarcoux]

But we can already exclude checks for specific files in Credo, which seems close to what Rubocop does.

True, this could be a way to start using Credo in projets with lots of issues.

Adding a way to automatically exclude files for specific checks would be awesome. It would generate lines such as this one below under checks:

%{
  configs: [
    %{
      name: "default",
      checks: [
        {Credo.Check.Warning.IExPry, files: %{excluded: ["lib/debug_server.ex"]}}`
      ]
    }
  ]
}

Regarding the second part of my issue about finding unneeded # credo:disable* comments, do you have any thoughts on this? By looking at how RuboCop does it, it implies gathering all Credo issues, then looking at the inline config comments to see if they match the issues found. This would be perhaps a post-processing check?

[rrrene]

Regarding the second part of my issue about finding unneeded # credo:disable* comments, do you have any thoughts on this?

Yes, that we should definitely do. I played around and came up with two potential ways to go about this:

1 - Make this a step after analysis triggered by something like --warn-on-redundant-config-comments:

This is more or less straight-forward: New switch enables new behaviour and output. We would have to define how we can detect this on CI, how it is exported to JSON, etc.

2 - Make this a check that can be enabled and disabled like any other (but has some special sauce like in Rubocop's case):

Making this a check would have its advantages: Checks/Issues can be easily enabled/disabled, be prioritized, given an individual exit status, exported in different formats etc.

And we can add more checks for other unused config entries in the future without adding more CLI switches.

Still, I am not sure which I like more. Any thoughts?

[dmarcoux]

I prefer the second option by making this a check. A CLI switch is good for a one-off thing, but this could be used for other checks as you mentioned.

[rrrene]

Thanks for reporting this 😀 It should be working on master.

You can try this by setting the Credo dep to

{:credo, github: "rrrene/credo"}

Please report back what you think 👍