misleading error: Cannot find package '.../package.json', when package.json exists

[isaacs]

Version

>=20.5.0

Platform

Darwin moxy.lan 22.6.0 Darwin Kernel Version 22.6.0: Wed Jul 5 22:22:05 PDT 2023; root:xnu-8796.141.3~6/RELEASE_ARM64_T6000 arm64

Subsystem

modules

What steps will reproduce the bug?

mkdir -p node_modules/whatever
echo {} > node_modules/whatever/package.json
node -e 'import("whatever")'

How often does it reproduce? Is there a required condition?

Happens when a package.json exists, in a package folder that exists, but which does not define a main or '.' export.

What is the expected behavior? Why is that the expected behavior?

The previous behavior was:

Error: Cannot find package '/Users/isaacs/dev/isaacs/resolve-import/test/fixtures/node_modules/whatever/' imported from /Users/isaacs/dev/isaacs/resolve-import/test/fixtures/[eval]

However, this is also not great, because it implies that the folder could not be found, when it clearly can be found.

What do you see instead?

Error: Cannot find package '/Users/isaacs/dev/isaacs/resolve-import/test/fixtures/node_modules/whatever/package.json' imported from /Users/isaacs/dev/isaacs/resolve-import/test/fixtures/[eval]

Additional information

The confusing bit is that it's saying it can't "find" the package.json file, which clearly does exist and is a valid package.json (albeit not one that defines a valid importable package).

A better error message would be something like:

Error: Package is not importable '/Users/isaacs/dev/isaacs/resolve-import/test/fixtures/node_modules/whatever/' imported from /Users/isaacs/dev/isaacs/resolve-import/test/fixtures/[eval]

[isaacs]

Also interesting note: it doesn't raise an error if there's a index.js in the folder, because in that case, it has a load target.

So the problem is really not the package.json not being findable, or the folder not being findable, but the package at node_modules/whatever not being something that Node can load successfully.

[himself65]

in master build

> node/out/Debug/node -e 'import("whatever")'
node:internal/modules/esm/resolve:186
  const resolvedOption = FSLegacyMainResolve(packageJsonUrlString, packageConfig.main, baseStringified);
                         ^

Error: Cannot find package '/Users/himself65/Code/node-issue-49674/node_modules/whatever/package.json' imported from /Users/himself65/Code/node-issue-49674/[eval]
    at legacyMainResolve (node:internal/modules/esm/resolve:186:26)
    at packageResolve (node:internal/modules/esm/resolve:771:14)
    at moduleResolve (node:internal/modules/esm/resolve:833:20)
    at defaultResolve (node:internal/modules/esm/resolve:1038:11)
    at ModuleLoader.defaultResolve (node:internal/modules/esm/loader:376:12)
    at ModuleLoader.resolve (node:internal/modules/esm/loader:345:25)
    at ModuleLoader.getModuleJob (node:internal/modules/esm/loader:221:38)
    at ModuleLoader.import (node:internal/modules/esm/loader:308:34)
    at importModuleDynamically (node:internal/process/execution:89:31)
    at importModuleDynamicallyWrapper (node:internal/vm/module:431:21) {
  code: 'ERR_MODULE_NOT_FOUND'
}

Node.js v21.0.0-pre

[himself65]

Please see https://github.com/nodejs/node/pull/49728

[HazelDaniel]

this is truly misleading

[joscha]

I just ran into this slightly cryptic message with a module-only package build. For future reference:

  "exports": {
    ".": {
      "import": "./dist/module.js",
      "require": "./dist/module.js"
    }
  },

fixes it for such a package.