Workflow never fails - Githubissues

I've tried everything I can think of, but it looks like it's impossible to get this workflow action to fail.

Here's my workflow:

name: CodingStandards
on:
  pull_request:
    paths:
      - "**.php"
      - "phpcs.xml"
      - ".github/workflows/phpcs.yml"
jobs:

  phpcs:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
        with:
          fetch-depth: 0

      - name: Install PHP_CodeSniffer
        run: |
          curl -OL https://squizlabs.github.io/PHP_CodeSniffer/phpcs.phar
          php phpcs.phar --version

      - uses: tinovyatkin/action-php-codesniffer@v1
        with:
          files: "**.php"
          phpcs_path: "php phpcs.phar --colors -v -vv"
          standard: "PSR12"
          scope: "file"

This just passes every time whether or not there's changed files with coding standards violations in them.

Here's the output:

Run tinovyatkin/action-php-codesniffer@v1
  with:
    files: **.php
    phpcs_path: php phpcs.phar --colors -v -vv
    standard: PSR12
    scope: file
Filter patterns: [ '**.php' ] true
{
  "added": [],
  "modified": [
    "app/Http/Controllers/Controller.php"
  ]
}

I've tried:

Using a phpcs.xml file with PSR12 standards
Putting PSR12 in quotes and not in quotes
Using scope file and omitting scope
Adding options to phpcs_path and using without options
Adding various PSR12 violations to the file in question
Using various forks of this repo in the hope one of them works

It's hard to tell what the output of the action should be. I would expect to see phpcs output but it looks like it's only printing a JSON object of changed files, so I don't know if it's actually running phpcs or not... if it's not running, that would explain why it's not failing, but I can't tell.

It's definitely recognising the modified file, and it definitely matches the glob in the filter pattern.

These are definitely coding standards violations because running phpcs manually at my end, the warnings do appear.

As mentioned, I think I've ruled out everything I can. Are there any other steps I can use to debug this?

tinovyatkin / action-php-codesniffer

Workflow never fails #87