How to resolve 'property-no-unknown' error in StyleLint?

I have a Wordpress project where Webpack and the StyleLint plugin are being used.

The problem is when compiling sass, it shows this error where it says it doesn't recognize the 'aspect-ratio' property that I'm using in my styles:

Unexpected unknown property "aspect-ratio" property-no-unknown

I tried adding 'ignoreProperties' to the config in the .stylelintrc.js file but it didn't work and it kept showing the error.

module.exports = {
  'extends': 'stylelint-config-standard',
  'rules': {
'no-empty-source': null,
'string-quotes': 'double',
'at-rule-no-unknown': [
  true,
  { 
    'ignoreProperties': [
      'aspect-ratio'
    ] 
  },
  {
    'ignoreAtRules': [
      'extend',
      'at-root',
    ],
   },
  ],
 },
};

How could I fix it? (I'm not very knowledgeable in StyleLint and this project was started by someone else.)

aspect-ratio is a known property in the latest version of Stylelint. You should update your copy of Stylelint to the latest version using:

npm install -D stylelint@latest

Alternatively, you can use the ignoreProperties secondary option, but you should use it on the property-no-unknown rule rather than the at-rule-no-unknown one as it's a property, not an at-rule:

module.exports = {
  'extends': 'stylelint-config-standard',
  'rules': {
'no-empty-source': null,
'string-quotes': 'double',
'at-rule-no-unknown': [
  true,
  {
    'ignoreAtRules': [
      'extend',
      'at-root',
    ],
   },
  ],
 },
 'property-no-unknown': [
  true,
  { 
    'ignoreProperties': [
      'aspect-ratio'
    ] 
  },
 ]
};