create_dir_all("") should complain about invalid filename

[rosik]

I tried this code:

fn main() {
    std::fs::create_dir_all("").unwrap();
}

The filename is invalid, so I've expected to see some error similar to posix utils:

$ mkdir -p ""
mkdir: cannot create directory ‘’: No such file or directory
$ mkdir ""
mkdir: cannot create directory ‘’: No such file or directory

Instead, nothing interesting happened, create_dir_all succeeded.

Meta

$ rustc --version --verbose
rustc 1.67.0-nightly (e0098a5cc 2022-11-29)
binary: rustc
commit-hash: e0098a5cc3a87d857e597af824d0ce1ed1ad85e0
commit-date: 2022-11-29
host: x86_64-unknown-linux-gnu
release: 1.67.0-nightly
LLVM version: 15.0.4

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 22.04.1 LTS
Release:        22.04
Codename:       jammy

[rosik]

P.S. std::fs::create_dir("") is fine:

$ cargo run
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 2, kind: NotFound, message: "No such file or directory" }', src/main.rs:2:29

I would expect to see the same message from create_dir_all

[edneedham]

Here is what I have found:

fn create_dir_all(&self, path: &Path) -> io::Result<()> { if path == Path::new("") { return Ok(()); } on line 2393 in the fs module

I think you're right in that the proper behaviour would be just to produce an error message in the
same way as posix utils. I don't know why this check exists, it doesn't seem to produce anything.

[ChrisDenton]

I don't know why this check exists

For some history see #23383. Though a lot has changed in 7 years.

[edneedham]

Thanks for the info, Chris.

[tbu-]

Since Path::new("abc").parent() == Some(Path::new("")), it makes sense for create_dir_all to succeed in this case. I'd say this needs documentation at most.