tsc doesn't output proper file case on Windows 10

[jednano]

TypeScript Version: 2.2.2

Code

irrelevant

Expected behavior:

On Windows 10, compiling Foo.ts writes a file named Foo.js to output folder.

Actual behavior:

If foo.js (lowercase) already exists in output folder, the new file contents of Foo.ts are written to foo.js, but the file name's case doesn't change.

This issue just bit me in the real world on the EditorConfig vscode extension.

Workaround

Deleting foo.js and running tsc again solves the problem; though, this is not ideal.

[smac89]

Isn't windows case insensitive when it comes to files?

So foo.js == Foo.js == fOO.js == FOO.js?

This makes sense why it doesn't create a new file, because it sees that a file with the same name already exists...so it simply overwrites it

[jednano]

@smac89 yes, I realize that, but it seems pretty important for the tsc compiler to "somehow" ensure the generated .js files are the correct case, consistent w/ the source .ts files. If not, other people will run into the same issue I just had to deal with, where Linux users are the only ones that are getting errors.

[mhegazy]

The compiler does not do any thing special here. this is the node fs apis on windows

c:\test>node
> const fs = require("fs");
undefined
> console.log("Foo.js first");
Foo.js first
undefined
> fs.writeFileSync("./Foo.js", "a");
undefined
> fs.writeFileSync("./foo.js", "a");
undefined
> console.log(JSON.stringify(fs.readdirSync("./"), undefined, 2));
[
  "Foo.js"
]
undefined
>
> fs.unlinkSync("./Foo.js");
undefined
>
> console.log("foo.js first");
foo.js first
undefined
> fs.writeFileSync("./foo.js", "a");
undefined
> fs.writeFileSync("./Foo.js", "a");
undefined
> console.log(JSON.stringify(fs.readdirSync("./"), undefined, 2));
[
  "foo.js"
]
undefined
>

[jednano]

Thanks @mhegazy! I posted an issue at nodejs/node#12521.

[jednano]

@mhegazy the Node.js ticket has been rejected as a Windows issue. I realize Windows has been like this, probably from the beginning, but do you think there's any chance this could go up the ladder at Microsoft? Not sure where to file the issue at this point.

[RyanCavanaugh]

Everything in Windows works the way it does to avoid breaking decades of backward compatibility. Zero chance this is changeable.

[jednano]

Thanks @RyanCavanaugh. If that's the case, I think this remains a TypeScript issue. I just did a little test and it turns out that the following works as expected:

fs.writeFileSync('Foo.js', 'bar');
fs.renameSync('Foo.js', 'foo.js');
fs.readdirSync('.');
[ 'foo.js' ]

The issue here, of course, is that it makes an assumption that the file already exists. I see two ways to solve this problem:

1. First, check if the file exists, using fs.exists.
2. Wrap the rename method in something like an _.attempt so that it fails silently.
3. Do a try...catch and ignore the error.

Would the TypeScript team be open to any of these options?

[RyanCavanaugh]

It seems like overkill to slow down every single build for the sake of not having to run npm run clean or whatever, once, when you change file casing in the extremely rare case where it actually matters.

[jednano]

I guess we're OK with tsc Foo.js -> foo.js then, as an edge case.