On 2/6/23 11:40, Imobach Gonzalez Sosa wrote:
Hi all,
As a Hack Week project, Josef and I started to work on a Rust-based command line interface[1] for D-Installer. My primary purpose was to determine whether it is a good language for building this tool. Moreover, I wanted to put my (limited) knowledge of the language into practice.
TL;DR; the experience was really positive. Although it is far from finished, we managed to build a minimal CLI that allows setting/getting configuration values (using YAML and JSON as output formats). You can find more details in the Running section[2] of the README.
Now, I will comment on some aspects that I found interesting. I hope you enjoy the reading :-)
# The main obstacle
Funny enough, the main "problem" we found was unrelated to Rust. It was, instead, the gap between our new CLI design (+ the auto- installation specification) and the D-Bus API. To fill the gap, we decided to keep an in-memory representation of D-Installer's settings (see the Settings and related structs[3]) and implement a separate mechanism to read/write those settings (see the Store struct[4]).
# Procedural macros
We found out that to set or get those configuration values, we needed to determine the name of the method/function to call at runtime. That's trivial with Ruby, but not with Rust without writing one line per each possible function. So we implemented a proc-macro[5] that generates the code for us. Beware that these macros are different to C/C++ ones and, among other things, they are written in Rust and give you access to the AST.
# Abstraction level
Rust cannot offer the same abstraction level as Ruby, period. But it has an expressive type system and powerful tools for meta-programming if needed. So when writing this CLI, I felt quite comfortable with the level of abstraction.
# Error messages are helpful
Most of the time, compiler error messages make sense. Apart from an explanation, it usually gives you some hints to solve the issues. However, if the error implies lifetimes, generics and so on, it can be hard to understand what is happening behind the scenes.
# Extensive documentation
Apart from "the book"[6], the standard library documentation is rather complete. However, it can be intimidating if you do not know the basis.
# Closing thoughts
As said before, the experience was really positive and I enjoyed a lot working on this project. There were a few things that we wanted to try, like calling Rust code from Ruby or using the async support, but we ran out of time.
My main question now is: should we use this as the base for our D- Installer CLI or should we go back to our Ruby-based implementation?
Regards, Imo
[1] https://hackweek.opensuse.org/22/projects/rewrite-the-d-installer [2] https://github.com/imobachgs/dinstaller-rs#running [3] https://github.com/imobachgs/dinstaller-rs/blob/update-readme/dinstaller-lib... [4] https://github.com/imobachgs/dinstaller-rs/blob/update-readme/dinstaller-lib... [5] https://github.com/imobachgs/dinstaller-rs/blob/update-readme/dinstaller-der... [6] https://doc.rust-lang.org/book/ [7] https://www.rust-lang.org/tools
Thanks for the summary! Very interesting, indeed. About deciding whether to continue with Rust or not, I would put several aspects on the balance: * Do we gain any use cases? Probably yes. For example, if the CLI is able to run commands remotely, then we don't need ruby deps in the system. * Is Rust a good option for other future migrations? Right now D-Installer uses a lot YaST logic, but we could start implementing new features in a separate Rust based backend. * In case of continuing with the Rust based CLI, more people in the team should start learning Rust. I think this is a positive thing, just commenting to make clear we don't want silos anymore. * Is there any other options to consider? Maybe we could do the exercise of implementing something similar with other modern language, for example Go, just to compare. * Having a team that speaks Ruby, is Rust the best migration? If not, are there good reasons to pay the effort? And for sure there are more things to consider. BTW, I am all for learning Rust. I am only expressing that officially migrating to another language is a difficult decision ;). Thanks a lot Imo and Josef. Great work! Regards, Iván -- José Iván López González YaST Team at SUSE LINUX GmbH IRC: jilopez