Tracking Issue for fs_try_exists

[Kixunil]

Feature gate: #![feature(path_try_exists)]

This is a tracking issue for try_exists() method on std::path::Path.

This method is similar to exists() method except it does not silently ignore errors that made it impossible to find out if the path actually exists (e.g. lack of permission on parent dir). Thus it naturally returns io::Result<bool> instead of just bool.

Public API

mod fs {
    pub fn try_exists<P: AsRef<Path>>(path: P) -> Result<bool>;
}

impl Path {
    #[stable(since = "1.63.0")]
    pub fn try_exists(&self) -> io::Result<bool>;
}

Steps / History

• Added try_exists() method to std::path::Path #81822
• Windows implementation of feature path_try_exists #85060
• Stabilize Path::try_exists() and improve doc #97912

Unresolved Questions

• None yet.

[ChrisDenton]

Could try_exists be added as a free function to std::fs and then the std::path::Path method forwards to that? This would be similar to the metadata function.

My motivation for this is to make it easier for platforms to override the metadata based implementation.

[Kixunil]

In the internals discussion @matklad pointed out that is_file() and is_dir() have same issue. I believe it may be even worse in their case. I wonder would it be reasonable to add those method within the scope of this feature or as a separate change?

[roblabla]

Since #85060, there's now std::fs::try_exists but no std::fs::exists (the method only exists on Path). This is somewhat confusing, especially since the documentation for std::fs::try_exists says:

As opposed to the exists() method, this one doesn’t silently ignore errors unrelated to the path not existing.

Without linking the appropriate exists method.

I think if we're going to have an std::fs::try_exists, we'll want to make an std::fs::exists method as well for symmetry.

[ChrisDenton]

I think there are a number of options here:

• Add std::fs::exists as you suggest.
• Don't stabilize std::fs::try_exists. I'd still want there to be some kind of fs::try_exists so that different platforms can specialize the implementation. But that can be purely internal to the standard library.
• Keep the current API but improve the docs. The original rationale for not having an std::fs::exists is that Path::exists is just a convenience wrapper around std::fs::metadata(path).is_ok(). A similar rationale could be applied when Path::exists is implemented as std::fs::try_exists(path).unwrap_or(false).

[Kixunil]

@roblabla clearly the doc was copied from Path::try_exist. Would be nice to fix.

[ChrisDenton]

I've submitted the small PR above which you may want to review.

[joshtriplett]

Nominating to consider stabilization.