hangs forever while scanning CSS file

[divinity76]

Describe the bug phpcs hangs forever while scanning the attached css file: fontAwesomeIE7.css.zip

Code sample see the attached css file (too large to comfortably inline.)

Custom ruleset no custom ruleset..

To reproduce Steps to reproduce the behavior:

1. unzip the attached css file
2. Run ./vendor/bin/phpcs -p fontAwesomeIE7.css -v
3. check back 10 hours later, see that it's still working on that file, clearly frozen.. using 100% cpu of 1 core.

root@x2ratma:/home/hans/projects/phpstan# time ./vendor/bin/phpcs --runtime-set testVersion 8.1 -p fontAwesomeIE7.css -v
Registering sniffs in the PEAR standard... DONE (28 sniffs registered)
Creating file list... DONE (1 files in queue)
Changing into directory /home/hans/projects/phpstan
Processing fontAwesomeIE7.css
14:31

^C
real    499m15.578s
user    447m50.731s
sys     1m13.497s

root@x2ratma:/home/hans/projects/phpstan# ls^C
root@x2ratma:/home/hans/projects/phpstan# time ./vendor/bin/phpcs -p fontAwesomeIE7.css -v
Registering sniffs in the PEAR standard... DONE (28 sniffs registered)
Creating file list... DONE (1 files in queue)
Changing into directory /home/hans/projects/phpstan
Processing fontAwesomeIE7.css

Expected behavior not freeze

Versions (please complete the following information):

• OS: Ubuntu 20.04 x84-64
• PHP: 7.4.3
• PHPCS: 3.7.0-dev
• Standard: N/A

Additional context was initially discovered with PHPCompatibility and reported over at https://github.com/PHPCompatibility/PHPCompatibility/issues/1337

[jrfnl]

Additional info: the scope map recursion goes into an infinite loop on that file.

[gsherwood]

Support for non-PHP files is being removed from PHP_CodeSniffer and I'm not fixing any bugs for these file types. Please switch to another tool to check CSS standards.