(v2.18.1) dev does not work with yarn v2

[alker0]

I run yarn run snowpack dev and snowpack crashes with a message p.match is not a function.
This is what I get when I run yarn run snowpack dev --verbose:

[snowpack] Using cache folder: node_modules/.cache/snowpack/development
[snowpack] Cache out of date or missing. Updating...
[snowpack] p.match is not a function
[snowpack] TypeError: p.match is not a function
    at Function.resolveVirtual (/home/node/projects/snowpack-yarn-flat/.pnp.js:9665:21)
    at VirtualFS.mapToBase (/home/node/projects/snowpack-yarn-flat/.pnp.js:9702:22)
    at VirtualFS.fsMapToBase (/home/node/projects/snowpack-yarn-flat/.pnp.js:9622:19)
    at VirtualFS.readFilePromise (/home/node/projects/snowpack-yarn-flat/.pnp.js:9559:47)
    at PosixFS.readFilePromise (/home/node/projects/snowpack-yarn-flat/.pnp.js:9559:26)
    at Object.readFile (/home/node/projects/snowpack-yarn-flat/.yarn/$$virtual/snowpack-virtual-9373708e97/0/cache/snowpack-npm-2.18.2-f6575f32e2-0838bef34c.zip/node_modules/snowpack/lib/util.js:44:46)
    at /home/node/projects/snowpack-yarn-flat/.yarn/$$virtual/snowpack-virtual-9373708e97/0/cache/snowpack-npm-2.18.2-f6575f32e2-0838bef34c.zip/node_modules/snowpack/lib/scan-imports.js:228:36
    at run (/home/node/projects/snowpack-yarn-flat/.yarn/cache/p-queue-npm-6.6.2-b173c5bfa8-e95a48f421.zip/node_modules/p-queue/dist/index.js:157:104)
    at PQueue._tryToStartAnother (/home/node/projects/snowpack-yarn-flat/.yarn/cache/p-queue-npm-6.6.2-b173c5bfa8-e95a48f421.zip/node_modules/p-queue/dist/index.js:105:17)
    at /home/node/projects/snowpack-yarn-flat/.yarn/cache/p-queue-npm-6.6.2-b173c5bfa8-e95a48f421.zip/node_modules/p-queue/dist/index.js:171:18
    at new Promise (<anonymous>)
    at PQueue.add (/home/node/projects/snowpack-yarn-flat/.yarn/cache/p-queue-npm-6.6.2-b173c5bfa8-e95a48f421.zip/node_modules/p-queue/dist/index.js:152:16)
    at getLoadedFiles (/home/node/projects/snowpack-yarn-flat/.yarn/$$virtual/snowpack-virtual-9373708e97/0/cache/snowpack-npm-2.18.2-f6575f32e2-0838bef34c.zip/node_modules/snowpack/lib/scan-imports.js:222:62)
    at Array.map (<anonymous>)
    at Object.scanImports (/home/node/projects/snowpack-yarn-flat/.yarn/$$virtual/snowpack-virtual-9373708e97/0/cache/snowpack-npm-2.18.2-f6575f32e2-0838bef34c.zip/node_modules/snowpack/lib/scan-imports.js:231:56)
    at async Object.getInstallTargets (/home/node/projects/snowpack-yarn-flat/.yarn/$$virtual/snowpack-virtual-9373708e97/0/cache/snowpack-npm-2.18.2-f6575f32e2-0838bef34c.zip/node_modules/snowpack/lib/commands/install.js:46:33)

According to the callstack this error occurs in these lines in .pnp.js

static resolveVirtual(p) {
  const match = p.match(VIRTUAL_REGEXP); // <-- This is where the error occurs. 
  if (!match || (!match[3] && match[5])) return p;
  const target = ppath.dirname(match[1]);
  if (!match[3] || !match[4]) return target;
  // ...
}

When I insert console.log('p is', p) into this method and run snowpack dev --verbose, I get this:

[snowpack] p is /home/node/projects/snowpack-yarn-flat/src/scripts
[snowpack] p is /home/node/projects/snowpack-yarn-flat/src/scripts/index.ts
[snowpack] p is /home/node/projects/snowpack-yarn-flat/src/scripts/index.ts
[snowpack] p is URL {
  href: 'file:///home/node/projects/snowpack-yarn-flat/src/public/index.html',
  origin: 'null',
  protocol: 'file:',
  username: '',
  password: '',
  host: '',
  hostname: '',
  port: '',
  pathname: '/home/node/projects/snowpack-yarn-flat/src/public/index.html',
  search: '',
  searchParams: URLSearchParams {},
  hash: ''
}
[snowpack] p is URL {
  href: 'file:///home/node/projects/snowpack-yarn-flat/src/styles/404.pcss',
  origin: 'null',
  protocol: 'file:',
  username: '',
  password: '',
  host: '',
  hostname: '',
  port: '',
  pathname: '/home/node/projects/snowpack-yarn-flat/src/styles/404.pcss',
  search: '',
  searchParams: URLSearchParams {},
  hash: ''
}
[snowpack] p is URL {
  href: 'file:///home/node/projects/snowpack-yarn-flat/src/styles/index.pcss',
  origin: 'null',
  protocol: 'file:',
  username: '',
  password: '',
  host: '',
  hostname: '',
  port: '',
  pathname: '/home/node/projects/snowpack-yarn-flat/src/styles/index.pcss',
  search: '',
  searchParams: URLSearchParams {},
  hash: ''
}

This is my snowpack.config.js:

module.exports = {
  exclude: [
    '**/node_modules/**/*',
    '**/__test__/*',
    '**/*.@(spec|test).@(js|mjs)',
    '**/.pnp.js',
  ],
  plugins: [
    [
      '@snowpack/plugin-run-script',
      { cmd: 'tsc --noEmit', watch: '$1 --watch' },
    ],
    '@snowpack/plugin-babel',
    [
      '@snowpack/plugin-build-script',
      { cmd: 'postcss', input: ['.pcss'], output: ['.css'] },
    ],
  ],
  mount: {
    web_modules: '/web_modules',
    'src/public': '/',
    'src/styles': '/css',
    'src/scripts': '/js',
  },
  alias: {
    '@lib': './src/lib',
    '@web_modules': './web_modules',
  },
  installOptions: {
    installTypes: true,
  },
  install: [],
  devOptions: {
    bundle: false,
  },
};

With v2.17.1 it works with the same configuration.

[FredKSchott]

This appears to be a yarn bug. fs.readFile supports file URLs, but it looks like Yarn does not. Can you update yarn and retry?

Also, if still broken when you update yarn: What version of Node.js are you on?

[alker0]

I updated Yarn but the error still occurs.

$ node --version
v14.13.1
$ yarn --version
2.4.0

[alubbe]

We just got bit by this as well and have opened an issue with yarn directly: yarnpkg/berry#2229
By the way, it might also be related to yarnpkg/berry#1889
Fred, do you happen to know what change in snowpack has resulted in passing file URLs rather than strings?

[FredKSchott]

Nothing recent, but it may have only gone out in v2.18.0 last week. It was part of a conscious move to use file URLs more to get around differences between Win & Unix

[merceyz]

This has been fixed in yarnpkg/berry#2291

[alker0]

Currently, latest release does not contains that modification.
It needs to run yarn set version from sources instead of yarn set version latest.
I did it and now I can run snowpack dev again.