[ruby-core:109370] [Ruby master Bug#18947] Unexpected Errno::ENAMETOOLONG on Windows

Issue #18947 has been updated by inversion (Yura Babak).


austin (Austin Ziegler) wrote in #note-1:
> If Ruby does not have an application manifest (I don’t know whether it does or not)

As I understand it was added here — [[Win32] long path name support [Bug #12551]](https://github.com/ruby/ruby/pull/4505)

> There is a way to handle long paths on Windows whether or not this registry key is enabled: prefix the drive root with `\\?\` (which would be `'\\\\?\\' as `\` is an escape character). It means you can’t work with relative paths and you must always use `\` as the file separator, but it always works and definitely did when I was using Ruby on Windows back in 2004–2011.

It doesn't work for me, still `.children` raises an expectation for the existing folder:
`<internal:dir>:98:in 'open': Filename too long @ dir_initialize - \\\\?\\D:\\very_loo…oong_path (Errno::ENAMETOOLONG)`


----------------------------------------
Bug #18947: Unexpected Errno::ENAMETOOLONG on Windows
https://bugs.ruby-lang.org/issues/18947#change-98520

* Author: inversion (Yura Babak)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [x64-mingw-ucrt]
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
On Windows 10, I am working on a script to copy a complex folder structure.

Pathname and FileUtils work fine for me until there is a folder with a **very long path** (>260 chars).

Normally you cannot access such a folder with Ruby.
The next operations will raise `Errno::ENOENT`
``` ruby
Pathname.new(300_chars_path).children
FileUtils.mkpath(300_chars_path)
```


But there is a way in Windows to remove the MAX_PATH limitation.
You can find a small .reg file in this article:
https://docs.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation?tabs=registry

After changing this system option, things start to work strangely in Ruby.

This will now raise `Errno::ENAMETOOLONG`:
``` ruby
Pathname.new(300_chars_path).children
```

But at the same time, you can create a folder with such a long path and write-read a file in it
``` ruby
FileUtils.mkpath(300_chars_path)
file = Pathname.new(300_chars_path+'/file.txt')
file.write 'oooooooooo'
puts Pathname.new(300_chars_path+'/file.txt').read
```


So you can work with individual items but attempts to list such folders' content fail (`.children`, `.glob`, `.copy`, etc).
In my case, deep `.glob` is broken for all the parent folders of that deep long-path folder ((

The only way I found for listing is
``` ruby
require 'win32ole'
fso = WIN32OLE.new 'Scripting.FileSystemObject'
for file in fso.GetFolder(300_chars_path).files
    file.name
    file.path.length
end
```

But using this workaround breaks all my code workflow built on top of Pathname and FileUtils ((.

So for me, it looks like some operations with long-path folders are not working just because in Ruby there is a check for the path length and not a real operation problem. And in some places (see .mkpath) there is no such check and all works fine.

Also notice that other applications on Windows have no problems with long-path folders (like Total Commander).

Please consider reviewing if we really need to raise `Errno::ENAMETOOLONG` if the `LongPathsEnabled` option is enabled in the Windows registry.




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