require(".\\") doesn't resolve index.js on Windows

While looking at #15015 (comment) I noticed that the trailing slash check in _findPath was only keying off of a forward slash and not the backslash that Windows allows.

You can repro this by simply doing the following in a directory with an index.js

require(".\\") // throws
require("./") // will find the index.js

Other places in Node account for the backslash in Windows paths so this looks like an oversight.

Update:

It looks like if it's a two dot relative path to an index.js then it does work.

require("..\\") // work
require("..\\.") // works
require("../") // works
require("../.") // works

Also this

require("./..") // works
require(".\\..") // throws

Notes:

It looks like path.resolve handles these cases fine so it can be excluded from the problem.

path.resolve(".\\") // 'C:\\projects\\bar\\foo'
path.resolve(".\\..") // 'C:\\projects\\bar'

It looks like part of the issue is in Module._resolveLookupPaths because it's only looking for a forward slash

node/lib/module.js

Line 365 in a3555d0

request.charCodeAt(1) !== 47/*/*/)) {

Module._resolveLookupPaths("./", null)
[ './',
  [ '.',
    'C:\\projects\\bar\\foo\\node_modules',
    'C:\\projects\\bar\\node_modules',
    'C:\\projects\\node_modules',
    'C:\\node_modules',
    'C:\\Users\\jdalton\\.node_modules',
    'C:\\Users\\jdalton\\.node_libraries',
    'C:\\Program Files\\nodejs\\lib\\node' ] ]

but is snipped:

> Module._resolveLookupPaths(".\\", null)
[ '.\\',
  [ 'C:\\Users\\jdalton\\.node_modules',
    'C:\\Users\\jdalton\\.node_libraries',
    'C:\\Program Files\\nodejs\\lib\\node' ] ]

⚠️ Once Module._resolveLookupPaths is fixed though it'll run into issues with #15015.

@jdalton

@jdalton I think we could probably have windows normalize \\ to / in all cases [like the URL spec does], is there a case where \\ doesn't act like / in the existing usage of paths on win32?

Replace all backslashes with forward slashes in paths

Replace all backslashes with forward slashes in paths (#12)

@jdalton

@jdalton I think we could probably have windows normalize \\ to / in all cases [like the URL spec does], is there a case where \\ doesn't act like / in the existing usage of paths on win32?

I'm curious about the answer to @bmeck's question here, and also if this is still an issue?

@jdalton

@jdalton ^^^^

@jdalton

@nodejs/modules-active-members @jdalton Should this be closed? Or is this an issue that should be addressed?

There's been no further action on this. Closing, but given that it's not fully resolved, I'm putting this on the Futures project board so that it does not get lost.

@jasnell

@jasnell why would an inactive issue that's still a problem be closed?

An unresolved issue that no one ever looks at isn't useful either. These can always be reopened if someone intends to pick it up. Also, after I'm done taking a triage pass at all these stale old issues I'll be compiling a list of outstanding issues for each subsystem

How can anyone ever decide to pick it up if it's closed?

I've reopened but as I said, "I'm putting this on the Futures project board so that it does not get lost." and "after I'm done taking a triage pass at all these stale old issues I'll be compiling a list of outstanding issues for each subsystem" ...

Can confirm this issue has been fixed with all these paths:

require(".\\") // throws
require("./") // will find the index.js

require("..\\") // work
require("..\\.") // works
require("../") // works
require("../.") // works

require("./..") // works
require(".\\..") // throws

Tested versions:
v12.22.1
v14.16.1
v15.14.0
v16.0.0

As this appears to be fixed on all supported versions, I'm going to close it. Of course, if that's wrong and it's still an issue somewhere, please comment or re-open.

Oh, wait, no, there's still one problem left, right? require(".\\..") // throws

Nope, it's just quoted from the original post.

All cases do not throw errors

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require(".\\") doesn't resolve index.js on Windows #18299

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require(".\\") doesn't resolve index.js on Windows #18299

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jdalton commented on Jan 22, 2018

bmeck commented on Jan 24, 2018

Trott commented on Jul 20, 2019

Trott commented on Jul 20, 2019

Trott commented on Apr 22, 2020

jasnell commented on Jun 25, 2020

ljharb commented on Jun 25, 2020

jasnell commented on Jun 25, 2020

ljharb commented on Jun 25, 2020

jasnell commented on Jun 26, 2020

pd4d10 commented on May 4, 2021

Trott commented on May 4, 2021

Trott commented on May 4, 2021

pd4d10 commented on May 4, 2021

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