[win][fs] Some functions do not support tailing dot "." and space " " in a filename

[AlttiRi]

What version of Bun is running?

1.0.26

What platform is your computer?

Window 10

What steps can reproduce the bug?

import fs from "node:fs/promises";

for (const filename of [" spaces.txt ", ".dots.txt."]) {
    await fs.writeFile(filename, `data:"${filename}"`);

    try {
        console.log((await fs.readFile(filename)).toString());
    } catch (e) { console.error(e); }

    try {
        console.log((await fs.stat(filename)).size);
    } catch (e) { console.error(e); }

    try {
        await fs.unlink(filename);
        continue;
    } catch (e) { console.error(e); }

    try {
        const newName = filename.replaceAll(/^[ .]+|[ .]+$/g, "");
        await fs.rename(filename, newName);
    } catch (e) { console.error(e); }
}

What is the expected behavior?

data:" spaces.txt "
19
data:".dots.txt."
17

The " spaces.txt ", ".dots.txt." files have been created, read, then deleted.

What do you see instead?

ENOENT: No such file or directory
   errno: -2
 syscall: "open"
   path: " spaces.txt "

ENOENT: No such file or directory
   errno: -2
 syscall: "stat"

ENOENT: No such file or directory
   errno: -2
 syscall: "unlink"

ENOENT: No such file or directory
   errno: -2
 syscall: "rename"

ENOENT: No such file or directory
   errno: -2
 syscall: "open"
   path: ".dots.txt."

ENOENT: No such file or directory
   errno: -2
 syscall: "stat"

ENOENT: No such file or directory
   errno: -2
 syscall: "unlink"

ENOENT: No such file or directory
   errno: -2
 syscall: "rename"

The " spaces.txt ", ".dots.txt." files have been created, but not read, or deleted.

Additional information

Tailing / heading dots "." and spaces " " are allowed by NTFS, while Windows Explorer does not like them (it works buggy with them).

Do not end a file or directory name with a space or a period. Although the underlying file system may support such names, the Windows shell and user interface does not.

https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file

---

Bun can create (writeFile) them, but not read (readFile, stat) or delete (unlink, rename) them.

---

Rel:

• [win][fs] There is no support of long paths #8246

[AlttiRi]

By the way, I expected that it will not support ADS (Alternate Data Streams) too, but it works fine.

import fs from "node:fs/promises";

await fs.writeFile("ads.txt", `data:ads.txt`);
await fs.writeFile("ads.txt:metadata", `metadata:ads.txt`); // Alternate Data Stream

console.log((await fs.readFile("ads.txt")).toString());
console.log((await fs.readFile("ads.txt:metadata")).toString());
console.log((await fs.stat("ads.txt:metadata")).size);

await fs.unlink("ads.txt");

data:ads.txt
metadata:ads.txt
16

Anyway, it makes sense to add a test for it too in fs.test.ts, just in case.

[AlttiRi]

It's strange, but adding \\?\ does not help. While it should help.

https://learn.microsoft.com/en-us/dotnet/standard/io/file-path-formats#skip-normalization

Unless the path starts exactly with \\?\ (note the use of the canonical backslash), it is normalized.

Why would you want to skip normalization? There are three major reasons:

1. To get access to paths that are normally unavailable but are legal. A file or directory called hidden., for example, is impossible to access in any other way.
2. To improve performance by skipping normalization if you've already normalized.
3. To skip the MAX_PATH check for path length to allow for paths that are greater than 259 characters.

import fs from "node:fs/promises";
import path from "node:path";

for (const filename of [" spaces.txt ", ".dots.txt."]) {
    // const prefixed_filename = path.toNamespacedPath(path.resolve(filename)); // still does not work #8247
    const prefixed_filename = "\\\\?\\" + path.resolve(filename);
    console.log(prefixed_filename);

    try {
        await fs.writeFile(prefixed_filename, `data:"${filename}"`);
    } catch (e) { console.error(e); }

    try {
        console.log((await fs.readFile(prefixed_filename)).toString());
    } catch (e) { console.error(e); }

    try {
        console.log((await fs.stat(prefixed_filename)).size);
    } catch (e) { console.error(e); }

    try {
        await fs.unlink(filename);
        continue;
    } catch (e) { console.error(e); }

    try {
        const newName = filename.replaceAll(/^[ .]+|[ .]+$/g, "");
        await fs.rename(prefixed_filename, newName);
    } catch (e) { console.error(e); }
}

More over, in this case fs.writeFile fails too.

---

In this case the prefix works:

• [win][fs] There is no support of long paths #8246 (comment)

[AlttiRi]

Well, this works in Bun:

import fs from "node:fs/promises";
import path from "node:path";

for (const filename of [" spaces.txt ", ".dots.txt."]) {
    try {
        await fs.writeFile(filename, `data:"${filename}"`);
    } catch (e) { console.error(e); }

    const prefixed_filename = "\\\\?\\" + path.resolve(filename);
    console.log(prefixed_filename);

    try {
        console.log((await fs.readFile(prefixed_filename)).toString());
    } catch (e) { console.error(e); }

    try {
        console.log((await fs.stat(prefixed_filename)).size);
    } catch (e) { console.error(e); }

    try {
        await fs.unlink(filename);
        continue;
    } catch (e) { console.error(e); }

    try {
        const newName = filename.replaceAll(/^[ .]+|[ .]+$/g, "");
        await fs.rename(prefixed_filename, newName);
    } catch (e) { console.error(e); }
}

[AlttiRi]

fs.writeFile works without "\\\\?\\", but with the prefix it stops to work.
Other functions begin to work after adding of this prefix.
All examples above works in Node.js (regardless of the presence of the prefix).

[paperdave]

const prefixed_filename = "\\\\?\\" + path.resolve(filename);
is a simplified version of toNamespacedPath

i think once the path pr merges it might be worthwhile to use that api internally for all the fs stuff on windows. it probably should replace PosixToWinNormalizer, which is only really hitting SOME of the cases you present, and is why this only half works.