lilishop-uniapp/postcss.config.js

function requireUniPostcss() {
  const Module = require('module');
  const path = require('path');
  const postcssPath = require.resolve('@vue/cli-service/node_modules/postcss');
  const postcssPackagePath = require.resolve('@vue/cli-service/node_modules/postcss/package.json');
  const uniPostcssPath = path.normalize(
    require.resolve('@dcloudio/vue-cli-plugin-uni/packages/postcss')
  );
  const originalResolveFilename = Module._resolveFilename;

  Module._resolveFilename = function resolvePostcss(request, parent, isMain, options) {
    const parentFile = parent && parent.filename ? path.normalize(parent.filename) : '';
    if (parentFile === uniPostcssPath) {
      if (request === 'postcss') {
        return postcssPath;
      }
      if (request === 'postcss/package.json') {
        return postcssPackagePath;
      }
    }
    return originalResolveFilename.call(this, request, parent, isMain, options);
  };

  try {
    return require('@dcloudio/vue-cli-plugin-uni/packages/postcss');
  } finally {
    Module._resolveFilename = originalResolveFilename;
  }
}

module.exports = {
  plugins: [
    requireUniPostcss()(),
    require('autoprefixer')(),
  ],
};