source: frontend/node_modules/postcss-flexbugs-fixes/bugs/bug4.js

var postcss = require('postcss');

function shouldSetZeroBasis(basisValue) {
  if (!basisValue) {
    return false;
  }
  return basisValue === '0' || basisValue.replace(/\s/g, '') === '0px';
}

function properBasis(basis) {
  if (shouldSetZeroBasis(basis)) {
    return '0%';
  }
  return basis;
}

module.exports = function(decl) {
  if (decl.prop === 'flex') {
    var values = postcss.list.space(decl.value);

    // set default values
    var flexGrow = '0';
    var flexShrink = '1';
    var flexBasis = '0%';

    if (values[0]) {
      flexGrow = values[0];
    }

    if (values[1]) {
      if (!isNaN(values[1])) {
        flexShrink = values[1];
      } else {
        flexBasis = values[1];
      }
    }

    if (values[2]) {
      flexBasis = values[2];
    }

    decl.value = flexGrow + ' ' + flexShrink + ' ' + properBasis(flexBasis);
  }
};