Bug: Can't unignore file in flat config

[fisker]

Environment

Node version: v18.18.0
npm version: v9.4.2
Local ESLint version: v8.56.0 (Currently used)
Global ESLint version: Not found
Operating System: linux 5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/122.0.0.0 Safari/537.36

What parser are you using?

Default (Espree)

What did you do?

Configuration

export default [
  {
    ignores: ['files/**', '!files/should-be-linted.js'],
  },
  {
    rules: {
      'no-var': 'error',
    },
  },
];

var a = 1;

What did you expect to happen?

Should report error for files/should-be-linted.js file.

What actually happened?

You are linting "files", but all of the files matching the glob pattern "files" are ignored.

Link to Minimal Reproducible Example

https://stackblitz.com/edit/stackblitz-starters-48wnlw?description=Starter%20project%20for%20Node.js,%20a%20JavaScript%20runtime%20built%20on%20Chrome%27s%20V8%20JavaScript%20engine&file=package.json,eslint.config.js,files%2Fshould-be-linted.js&title=node.new%20Starter

Participation

• I am willing to submit a pull request for this issue.

Additional comments

No response

[mdjermanovic]

ignores: ['files/**', '!files/should-be-linted.js'],

This works as intended because, in flat config, these are minimatch patterns, and per the minimatch rules files/** also matches files/ directory (isaacs/minimatch#179), which is not unignored by a subsequent pattern so everything under it is still ignored.

The following patterns would ignore everything under foo/ except for files/should-be-linted.js:

ignores: ['files/*', '!files/should-be-linted.js']

I think we should explain this better in the documentation and migration guide.

[fisker]

Question: How to unignore file in files/? I can't figure out, it blocks me switch to flat config in Prettier prettier/prettier#15869.

[mdjermanovic]

Question: How to unignore file in files/? I can't figure out, it blocks me switch to flat config in Prettier prettier/prettier#15869.

The problem is that the following doesn't unignore jsfmt.spec.js files?

tests/format/**/*
!tests/format/**/jsfmt.spec.js

It's most likely because tests/format/**/* matches directories where jsfmt.spec.js files are, can you try with:

tests/format/**/*.js
!tests/format/**/jsfmt.spec.js

[fisker]

Thanks, it seems works! I'm going to use

tests/format/**/*.*
!tests/format/**/jsfmt.spec.js

[fisker]

I have to say it's really odd..

I guess, my patterns won't work if directory contains . or the file want be unignored doesn't contains . (eg: bin files without extensions).

Another thing is that it seems we treat patterns starts with / as absolute path, which is also different as before, that's why I removed all leading / in https://github.com/prettier/prettier/pull/15869/files

[mdjermanovic]

I guess, my patterns won't work if directory contains . or the file want be unignored doesn't contains . (eg: bin files without extensions).

I think this is the same problem as with .gitignore patterns, and the solution would be similar:

# first, ignore everything (files and directories)
tests/format/**/*

# then, uningore all directories
!tests/format/**/*/

# then, unignore specific files
!tests/format/**/jsfmt.spec.js

That said, some behavior of flat config ignore patterns does look odd, I'll double-check whether everything works as intended.

Another thing is that it seems we treat patterns starts with / as absolute path, which is also different as before, that's why I removed all leading / in https://github.com/prettier/prettier/pull/15869/files

This is intended. In flat config, patterns should not start with / .

This is different from .gitignore, where /a.js pattern matches only top-level a.js, while a.js pattern matches a.js at any level. In flat config, a.js pattern matches only top-level a.js, **/a.js should be used to match at any level, while /a.js is basically invalid. We should document this as well.

[fisker]

tests/format/**/*
!tests/format/**/*/
!tests/format/**/jsfmt.spec.js

Doesn't work as I tested, it will unignore all files.

[mdjermanovic]

tests/format/**/*
!tests/format/**/*/
!tests/format/**/jsfmt.spec.js

Doesn't work as I tested, it will unignore all files.

I'd expect this to ignore everything under tests/format/ except for jsfmt.spec.js files. I'll check why it doesn't work that way.

[mdjermanovic]

tests/format/**/*
!tests/format/**/*/
!tests/format/**/jsfmt.spec.js

Doesn't work as I tested, it will unignore all files.

I'd expect this to ignore everything under tests/format/ except for jsfmt.spec.js files. I'll check why it doesn't work that way.

Looks like a bug to me, I'm working on this.

[nzakas]

@mdjermanovic #17980 upgrades config-array, but you may want to add tests to cover this issue.

[mdjermanovic]

@mdjermanovic #17980 upgrades config-array, but you may want to add tests to cover this issue.

Yes, I'll add test cases.

[mdjermanovic]

Tests: #18018

I'm working on the docs now.