modules in node_modules not resolved when using lookupStartPath "."?

[sverweij]

It looks as though attempts to resolve external modules got jammed somewhere. Did I forget something? Should I pass something extra? Is it a deliberate deprecation?

Steps taken

Run the example from the README:

sample.js

const resolve = require("enhanced-resolve");
console.log(
  resolve.sync(".", "enhanced-resolve")
);

Expected

The resolved file path (something like ./node_modules/enhanced-resolve/lib/node.js) is printed to stdout.

Found

An error is thrown:

/Users/lalala/thing/node_modules/enhanced-resolve/lib/pathUtils.js:39
        switch (p.length) {
                  ^

TypeError: Cannot read property 'length' of undefined
    at getType (/Users/lalala/thing/node_modules/enhanced-resolve/lib/pathUtils.js:39:12)
    at join (/Users/lalala/thing/node_modules/enhanced-resolve/lib/pathUtils.js:145:10)
    at cachedJoin (/Users/lalala/thing/node_modules/enhanced-resolve/lib/pathUtils.js:181:15)
    at Resolver.join (/Users/lalala/thing/node_modules/enhanced-resolve/lib/Resolver.js:449:10)
    at /Users/lalala/thing/node_modules/enhanced-resolve/lib/ModulesInHierachicDirectoriesPlugin.js:40:50
    at Array.map (<anonymous>)
    at /Users/lalala/thing/node_modules/enhanced-resolve/lib/ModulesInHierachicDirectoriesPlugin.js:40:32
    at Array.map (<anonymous>)
    at /Users/lalala/thing/node_modules/enhanced-resolve/lib/ModulesInHierachicDirectoriesPlugin.js:39:14
    at _next0 (eval at create (/Users/lalala/thing/node_modules/tapable/lib/HookCodeFactory.js:33:10), <anonymous>:8:1)

Notes

• resolution of local paths works as expected (so filling out './sample' instead of 'enhanced-resolve' correctly yields 'sample.js'
• passing process.cwd() instead of "." does resolve to the correct file in node_modules.
• passing an explicit modules array to the options -> same error thrown
• tried the same with the create resolver and the async samples in the readme (with the same results)

The same code works as expected in enhanced-resolve@latest (currently 4.3.0)

Environment

• webpack webpack/enhanced-resolve#master (commit hash: bcf7ee8) against node 14, 12 and 10
• enhanced-resolve@5.0.0-beta.8 from npm against node 14

(both on OSX 10.15.5)

[sokra]

It has to be an absolute path. The readme always uses an absolute path at that location too.

[alexander-akait]

@sokra I think we can fix it for better DX

[sokra]

This is very performance sensitive...

[sverweij]

@sokra gotcha, clear!

Even though v4 wasn't supposed to be able to receive relative paths in lookupStartPath, for ppl migrating from v4 -> v5 it might be unexpected. Should this be documented as a breaking change in i.e. final release notes for v5?

[alexander-akait]

@sverweij yes, it is good to document it, you can send a PR to docs with this note.