wrap_comments breaks local links

[Emoun]

When wrap_comments=true, crate-local links in docs might get split over two lines, breaking them.

Where rustfmt won't break doc links that start with e.g. http, links starting with ../ are not recognized as links and may be split over two lines. Example:

/// [some_local_link](../super_package/module1/module2/module3/module4/struct.SomeStruct.html)
fn some_fn() {}

Running rustfmt results in the following:

/// [some_local_link](../super_package/module1/module2/module3/module4/struct.
/// SomeStruct.html)
fn some_fn() {}

This crate-local link will no longer work when rustdoc is run.

I have no prior experience with the rustfmt codebase, but I think the issue is with the following function:

// Path: rustfmt/rustfmt-core/rustfmt-lib/src/comments.rs

/// Returns `true` if the given string MAY include URLs or alike.
fn has_url(s: &str) -> bool {
    // This function may return false positive, but should get its job done in most cases.
    s.contains("https://") || s.contains("http://") || s.contains("ftp://") || s.contains("file://")
}

It seems to me to be the function that is responsible for URL recognition. It is clear it doesn't take crate-local links into account.
Looking at related issues, it seems rustfmt/rustfmt-core/rustfmt-lib/src/string::detect_url() has the same job, and might already take local links into account. Maybe use it instead?

I'd be willing to try and create a test and fix PR if you give the go-ahead.

[calebcartwright]

hi @Emoun, thanks for reaching out as well as the interest and willingness to contribute a fix!

I'm fairly confident that this issue has already been fixed, but just hasn't been released yet. See #4023 where this was previously reported and #4042 which resolved the issue.

At the moment we're primarily focused on getting a 2.0 release of rustfmt shipped and active development for 2.0 is being done on the master branch. The fix for this issue is available on master/rustfmt 2.0, but it simply hasn't been backported to a published rustfmt 1.x release yet.

We're also trying to only publish new 1.x versions of rustfmt to address major breaking issues, but if/when we do have another 1.x release we'll try to bundle in this fix as well. In the interim you could consider using rustfmt 2.x by building from source, and/or temporarily disabling comment wrapping in your config.

Accordingly, I'm going to close this but please feel free to re-open if you are able to reproduce this with the 2.x version of rustfmt from source.

Hopefully we'll have the fix available in a released version of rustfmt soon!

[Emoun]

I can confirm that building from source doesn't exhibit this problem. Probably should have tried that before making the issue.

[calebcartwright]

No worries, thanks for reaching out and verifying!