Support for Replacing Directory Targets

[Oops418]

Hi, thank you for the great work on this project!

I'm wondering if there is any plan to support replacing a directory (e.g. .app bundles on macOS) using self-replace.

While using self_update, I encountered an issue when trying to update an app on macOS where the target is an .app bundle — which is essentially a directory. See the related issue here: jaemk/self_update#145

After reviewing how self_update handles updates, it seems like the logic for replacing such targets might be a better fit in the upstream self-replace crate. Hence, I’d like to raise this feature request.

Would it be possible to consider adding support for replacing directory targets?

Thanks for your consideration!

[mitsuhiko]

I'm happy to accept a PR for this. I'm personally not entirely sure what the right logic here would be yet but I think it's worth exploring.

[mitsuhiko]

I'm somewhat suspicious of this request. I feel like there is more to it that I don't fully understand. In particular there is now way that a bundle can be replaced in-place without creating all kinds of oddities to the currently running application and this entire library will not work if you also have .dylibs in place which might be the case for bundles.

I worry that you will need something like a real updater for macos bundles in practice.

[Oops418]

Your concern is very valid. From what I understand, frameworks like Sparkle address this by either waiting for the target .app to quit or forcibly terminating it before replacement (reference). Then they perform the replacement using atomic techniques, often taking advantage of APFS features (reference), or fall back to simple move-based strategies if needed.

The challenge here is that Sparkle and something like that is quite Objective-C/Swift-centric on MacOS, which makes integration into a Rust-based project more complex and, frankly, not very elegant.

So there is a idea of adding an optional feature to self_replace that can handle a self-replacement of the .app bundle — essentially enabling self-updating behavior within Rust. The idea is that self_update would be responsible for checking and downloading updates, while self_replace would handle the local replacement. It wouldn’t be as comprehensive as Sparkle, but could serve as a simpler cross-platform solution, especially if we also implement a similar feature for Windows.

If you think this approach makes sense, I’d be happy to explore it further and prototype a solution :)

[mitsuhiko]

Yeah I think the request is valid I just don't know how to best do it that it works in practice. But very happy to get something into it.

[houqp]

I have been looking for this feature for my app as well, let me know if there is anything I can help with the implementation.

Here is another reference on how it's handled in tauri in pure rust, which works very well:
https://github.com/tauri-apps/plugins-workspace/blob/d8e627522cda6be903459bc9095dcd4acccafdc9/plugins/updater/src/updater.rs#L1091