package.json "main" may specify a directory; spec says it may not

[ghost]

• Version: v7.1.0
• Platform: Windows 10 Enterprise version 1607, 64-bit
• Subsystem: ?

To reproduce

a.js

console.log(require.resolve("./m"));
console.log(require.resolve("./m2"));

m/package.json

{ "main": "main" }

*m/main/index.js

(empty file)

m2/package.json

{ "main": "main" }

m2/main/package.json

{ "main": "main2" }

m2/main/main2.js

(empty file)

When I run this, I get:

C:\Users\anhans\work\sample\package\m\main\index.js
module.js:474
    throw err;
    ^

Error: Cannot find module './m2'

Explanation

Based on the spec, I would not expect the first require.resolve call to succeed.

The important line is c. LOAD_AS_FILE(M) at the end of LOAD_AS_DIRECTORY step 1.
It appears to not be LOAD_AS_FILE because m/main/index.js is loaded, but not LOAD_AS_DIRECTORY either because m2/main/main2.js is not loaded (i.e., package.json is not looked up recursively).

This is relevant because we want to follow the node module-resolution spec in our own module loader; but we also want it to work for a real packages like common-tags, which specifies the lib directory for its main. See microsoft/TypeScript#12198.

[Fishrock123]

I suspect the "spec" is out of date. We probably can't change the running behavior of this.

[bnoordhuis]

It is, see #4595 (comment) for another example.

[bmeck]

fixed 608ea94