• 40 Posts
  • 2.21K Comments
Joined 6 years ago
cake
Cake day: May 31st, 2020

help-circle



  • Yeah, the latter is certainly a big part of it. The way to make it compile-safe is to use macros to generate code, so that my users can write e.g. Package::my_frontend.version and that gives them the version of their frontend package.
    Writing such macros, i.e. writing code to generate code, is certainly something I haven’t done a ton of yet, because you practically cannot justify doing that in an application codebase, only in a library, so it is new stuff that I learn.

    But well, you did already call it a “nice abstraction”, which is another big part where my excitement comes from and where I think, the special nerdery is necessary.
    Others might build projects which are visually tangible, like a sexy GUI, or which do something tangible, for example a colleague (who I will absolutely not deny his own special nerdery) is currently building a driver for a motor. If that driver works, you can see a motor moving in the real-world. Even non-nerds can at least tell that something is happening.

    But with my project, my success is that you can write Package::my_frontend instead of Package::from_str("my_frontend")?. And that if you rename the package to super_duper_frontend, that the compiler will tell you to fix the code rather than it only breaking once you actually run the build code for the frontend.
    No chance of explaining to non-coders why this is exciting or even just when you’re successful.



  • On Monday, one of our students at $DAYJOB asked me what projects I do in my freetime. After I infodumped on her for half an hour, she asked in disbelief “And you do these in your freetime, without being paid?”.

    Like, mate, did you not listen how feckin’ excited I got just then? Of course, I do these in my freetime.

    To be fair, though, the last project I told her about is very dry. It’s a library to help automate CI builds. And the thing I’m thrilled to build is a compile-safe API for accessing the packages in your workspaces. Like, yeah, it does take a special kind of nerd to get excited about that…






  • In many cases, you don’t need an equivalent to finally, because the cleanup is automatically handled via the Drop trait, which runs cleanup code when the object is freed from memory (similar to “destructors” in some other languages).
    Because of Rust’s whole ownership thingamabob, it’s generally entirely deterministic when this code will run (at the closing brace for the scope in which the object is defined, unless you pass that object outside of that scope).

    In other cases, you don’t need a finally, because nothing forces you to bubble up errors instantly. You can make a call which fails, store the error in a variable, run your cleanup steps and then return the error at the end of you function.

    Sometimes, however, you do want to bubble up errors right away (via ? or early return), typically so you can group them together and handle them all the same.
    In that case, you can run the cleanup code in the calling function. If you don’t to want to make it the responsibility of the caller, then pull out a small function within your function, so that you become the caller of that small function and can do the cleanup steps at the end of your function, while you do the bubbling within the smaller function.
    There’s also ways to make that less invasive via closures (which also serve as a boundary to which you can bubble errors), but those are somewhat complex in Rust, due to the whole ownership thingamabob.

    I will say, I do sometimes feel like Rust could use a better way to handle doing something before the error bubbles up. But generally speaking, I don’t feel like a finally is missing.


  • You can use the anyhow crate for something quite similar to exceptions: https://crates.io/crates/anyhow

    In terms of how it actually fits into Rust, you want to use anyhow for application code. If you’re writing a library, then anyhow is a no-go, because users cannot match on different error classes with it. (Much like you would want custom exception classes, so that users can catch them in different catch branches and handle them differently.)

    Every so often, you will also need matchable error classes within your application code, then you would have to replace anyhow with a custom error type there, too, of course.

    I will also say, IMHO it is fine to use anyhow even while you’re learning Rust. It is so easy that you kind of skip learning error handling, which you will need to learn at some point, but you can still do that when you actually need it.






  • Back in 2010, the OpenOffice devs had to abandon that name for trademark reasons¹, so they renamed to LibreOffice and continued developing under that name.

    OpenOffice theoretically also still exists, but it’s hardly getting updates. Unless you specifically like software from 2010 (including some security vulnerabilities, I believe), you want to use LibreOffice.

    ¹) The OpenOffice trademark was owned by Sun Microsystems, which got bought by Oracle. Oracle has a very bad reputation, so the devs did not care to wait around for Oracle to fuck everything up.




  • We deployed a client software in a Docker container on Windows 10. It could not connect to the backend, even though we saw SYN packages originating from it.
    So, we ran WireShark on the Windows host and saw that the SYN-ACK packages from the backend were arriving there, too, but no ACK came through to complete the TCP handshake.

    Eventually, we rolled out a network debugging container on that Windows host and then could see in the tcpdump, that the SYN-ACK packages, which arrived on the Windows host, just did not show up in the container. Hyper-V or something was quietly dropping them.

    Other network connections were working fine, just the SYN-ACK from our backend triggered this.