On Windows, Node can be inconsistent in what case builtin functions use for drive letters

[thorn0]

• Version: 6.0.0
• Platform: Windows 7 x64
• Subsystem: path, module, process

When cmd.exe is run via a shortcut that has a lowercase drive letter in its 'Start in' field (e.g. d:\dev) and Node is run from this cmd instance, Node's builtin functions behave in an unexpected way. Some of them return the drive letter in upper case (D:\dev\foo) whereas the other in lower (d:\dev\foo).

test.js:

var exprs = ['__dirname', '__filename', 'require.resolve("./test")', 
    'require("path").resolve("test.js")', 'process.cwd()'];
for (var expr of exprs) {
    console.log(expr, eval(expr));
}

In cmd:

d:\dev\foo>node test
__dirname D:\dev\foo
__filename D:\dev\foo\test.js
require.resolve("./test") D:\dev\foo\test.js
require("path").resolve("test.js") d:\dev\foo\test.js
process.cwd() d:\dev\foo

If I change the case of the drive letter in the "Start in" field of the shortcut for cmd, everything becomes consistent.

D:\dev\foo>node test
__dirname D:\dev\foo
__filename D:\dev\foo\test.js
require.resolve("./test") D:\dev\foo\test.js
require("path").resolve("test.js") D:\dev\foo\test.js
process.cwd() D:\dev\foo

This leads to issues like webpack/webpack#2362.

So what can be done about it?

1. It'd be great if Node always used upper case.
2. Also now Node resolves d:\test.js and D:\test.js as two different modules. Should it stay like this?

d:\dev\foo>echo console.log('load')>bar.js
d:\dev\foo>node
> require('d:\\dev\\foo\\bar.js')
load
{}
> require('d:\\dev\\foo\\bar.js')
{}
> require('D:\\dev\\foo\\bar.js')
load
{}

[jhamhader]

#3594 might be part of this issue.

[orangemocha]

1. It'd great if Node always used upper case.

Node changed behavior a few times in the past. From what I can reacall, what was finally deemed the 'proper' way was to never have Node normalize the drive case. So it could change based on the process current directory, as you noted, but at least it would be consistent everywhere internally.

Are you seeing any place where Node is changing the case and making it different than process.cwd or what was passed in the command line? If so it should be considered a bug, IMO.

Also now Node resolves d:\test.js and D:\test.js as two different modules. Should it stay like this?

I think it shouldn't. See nodejs/node-v0.x-archive#6774. I'll add it to my todo list to revive that.

[thorn0]

Are you seeing any place where Node is changing the case and making it different than process.cwd or what was passed in the command line?

Yes.

d:\dev\foo>node test
__dirname D:\dev\foo
__filename D:\dev\foo\test.js
require.resolve("./test") D:\dev\foo\test.js
require("path").resolve("test.js") d:\dev\foo\test.js
process.cwd() d:\dev\foo

[Jeff-Lewis]

YES

Even when using only relative paths to modules './../myModule', something changes require.resolve from using the uppercase C:\ path of a module initially to use the lowercase c:\ path during the loading of a project.

In our case, from looking at the require.cache order of modules, it switches from "C:\..." to "c:\.." after completing the first cycle of module reference chains. My guess is that it might have something to do when require is resolving circular referencing module chains and starts working on the 2nd and n- number of loops to resolve modules.

When this occurs, it can load some modules twice which we just experienced when cwd() is initially set with an uppercase "C:\..."

*** Edited ***
Removed suggestion about using uppercase drive letters. It's not a good suggestion...

node: v4.4.4
Windows 10

/cc @mousetraps

#3594
nodejs/node-v0.x-archive#6774
nodejs/node-v0.x-archive#7031
nodejs/node-v0.x-archive#8145
nodejs/node-v0.x-archive#7806

[orangemocha]

In cmd:

d:\dev\foo>node test
__dirname D:\dev\foo
__filename D:\dev\foo\test.js
require.resolve("./test") D:\dev\foo\test.js
require("path").resolve("test.js") d:\dev\foo\test.js
process.cwd() d:\dev\foo

This exemplifies the issue very well, thank you!

We could attempt to normalize the casing of __dirname and __filename to match that of process.cwd(). That might have other unwanted side effects though. The real answer is to always make case insensitive path comparisons on Windows.

This is on my queue of fixes.

[RobCannon]

This is causing issues in webpack. Waiting eagerly for a fix.