Failure to resolve dependencies from nested symlinked directories when bundling

[onebytegone]

When bundling code that imports a dependency through nested symlinked directories, esbuild fails with Could not read from file. However, running the same code using node works.

Background: I'm looking to use esbuild for projects in a monorepo that has some fanciness with symlinks for various legacy reasons. The project structure looks like:

$ tree
.
├── bar
│   └── foo -> ../foo
├── baz
│   └── bar -> ../bar
├── foo
│   └── index.js # imports "../qux"
├── in.js # imports "./baz/bar/foo"
└── qux
    └── index.js

If the symlinks were resolved, a project's structure would look something like:

$ tree
.
├── baz
│   └── bar
│       ├── foo
│       │   └── index.js # imports "../qux"
│       └── qux
│           └── index.js
└── in.js # imports "./baz/bar/foo"

Putting aside debates about whether this structure is a Good Idea:tm: or not (there's definitely part of me that says this symlinking example is a little crazy), it seems like this might be an edge-case in esbuild. Both node and Webpack resolve the symlinks without issue.

MVCE

Download: symlink-mvce.zip

$ tree -I node_modules
.
├── bar
│   └── foo -> ../foo
├── baz
│   └── bar -> ../bar
├── foo
│   └── index.js
├── in.js
├── package-lock.json
├── package.json
└── qux
    └── index.js

6 directories, 5 files
$ cat in.js
'use strict';

const foo = require('./baz/bar/foo');

if (foo.foo === 123) {
   console.log('ok', foo);
} else {
   throw 'fail';
}
$ cat foo/index.js
'use strict';

const qux = require('../qux');

module.exports = { foo: 123, ...qux };
$ cat qux/index.js
'use strict';

module.exports = { qux: 321 };

Versions

$ node -v
v16.15.0
$ npm -v
8.5.5
$ ./node_modules/.bin/esbuild --version
0.16.10

Output

$ node in.js # Code works when run with node
ok { foo: 123, qux: 321 }
$ ./node_modules/.bin/esbuild in.js --bundle
✘ [ERROR] Could not read from file: /private/tmp/mvce/baz/foo/index.js

    in.js:3:20:
      3 │ const foo = require('./baz/bar/foo');
        ╵                     ~~~~~~~~~~~~~~~

1 error

FWIW, the --preserve-symlinks behavior is as expected:

$ ./node_modules/.bin/esbuild in.js --bundle --preserve-symlinks
✘ [ERROR] Could not resolve "../qux"

    baz/bar/foo/index.js:3:20:
      3 │ const qux = require('../qux');
        ╵                     ~~~~~~~~

1 error
$ node --preserve-symlinks in.js
node:internal/modules/cjs/loader:936
  throw err;
  ^

Error: Cannot find module '../qux'
Require stack:
- /private/tmp/mvce/baz/bar/foo/index.js
- /private/tmp/mvce/in.js
    at Function.Module._resolveFilename (node:internal/modules/cjs/loader:933:15)
    at Function.Module._load (node:internal/modules/cjs/loader:778:27)
    at Module.require (node:internal/modules/cjs/loader:1005:19)
    at require (node:internal/modules/cjs/helpers:102:18)
    at Object.<anonymous> (/private/tmp/mvce/baz/bar/foo/index.js:3:13)
    at Module._compile (node:internal/modules/cjs/loader:1105:14)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1159:10)
    at Module.load (node:internal/modules/cjs/loader:981:32)
    at Function.Module._load (node:internal/modules/cjs/loader:822:12)
    at Module.require (node:internal/modules/cjs/loader:1005:19) {
  code: 'MODULE_NOT_FOUND',
  requireStack: [
    '/private/tmp/mvce/baz/bar/foo/index.js',
    '/private/tmp/mvce/in.js'
  ]
}

Related

• Failure to resolve yarn-linked packages when bundling #766
• Allow configuring of symlink resolve behavior #781

[onebytegone]

At the moment, I think this is related to the symlink resolution code here. I'm happy to investigate further. However, figured it'd be better to create an issue before going too far.

[evanw]

Thanks for the thorough issue description and PR. I'll publish your fix soon.