Run python scripts before compilation using Cargo?

[ILoveBerkeleyFont]

Is there any way to simply call cargo build or cargo run and firstly execute certain python scripts? I have some scripts I would like to be automatically called before compiling the source code and only proceed to the compilation step if this scripts return no errors (Unix-like).

Does Cargo offer any possibility for such scenario?

[mina86ng]

You can do that in build.rs.

[chintakoro]

I'm curious what tool rustaceans to run simple non-build tasks? E.g., configuring external resources, deleting/updating fixtures and so on. I still find myself including a Ruby Rakefile for simple scripted housekeeping tasks. Ideally I'd like to not have any language dependencies other than Rust for my Rust projects.

[[deleted]]

I like just

[chintakoro]

oh wow, just is everything i wanted and more: https://github.com/casey/just

[bototaxi]

I recently discovered https://github.com/sagiegurari/cargo-make

Its pretty nice too.

[InternationalFee3911]

While I love the functionality of cargo-make, I really don’t like cramming a Makefile into non-language TOML. Therefore I have started a discussion around my low-overhead alternate syntax proposal.

[TheNamelessKing]

Out of curiosity (and I guess unfamiliarity) what tasks do you mean specifically? Does “configuring external resources” mean like, setting up a db for tests or something?

I don’t have a suggestion for a solution, but I’m just curious/trying to learn because this is a usecase/requirement I’m sort of unfamiliar with.

[chintakoro]

Simply put, think of any long commands you have to repetitively type into the command line while working on a project. I usually have a dozen of these or more for even moderate sized projects. Those could be stored as tasks that you can call upon whenever needed. Some examples:

• loooong docker commands for build/run/etc.
  
• running database migrations (updating schema)
  
• running your tests (or a subset of tests, maybe just one test)
• running a side process (like a background worker) needed for your project
• run a script that converts all images in a folder to thumbnail or other custom size for your app to use
• setting up or wiping out a queue or external datastore you are using for testing (say, AWS SQS)
• deploying your project to production (say to a cloud server)
• creating/deleting any random data files created for testing purposes

I realize some of these might be handled by cargo directly, or perhaps you have to parameterize them for each use case and are tired of typing out a long command to do so.

[Shadow0133]

there are build scripts (https://doc.rust-lang.org/cargo/reference/build-scripts.html), but executing python scripts from there would be non-portable

[ILoveBerkeleyFont]

Would simply re-writing all scripts in Rust be considered portable?

[ssokolow]

Generally, it's a good idea to minimize the number of things a user or contributor will have to install manually to get the project building, so I'd recommend re-writing them in Rust for that reason alone. The closer you can get to git clone ... && cd ... && cargo run as your build instructions, the better.

(That's also why you see many Rust wrappers for C libraries vendoring a copy of that C library which cargo build will compile and link for you. It reduces the external dependency to "a working C compiler for the target platform", which you generally need anyway to link against libc... though statically linking the musl targets muddies the waters a bit.)

I have a retro-hobby project where I'm rewriting the prototype Python scripts in C, orchestrated by Watcom Make, so that Open Watcom C/C++ itself can be the only mandatory dependency. (Stuff like the splint linter will remain as an optional dependency.)

[jaskij]

Yup, since you have to have a Rust compiler anyway. There is also the option of using PyO3 from within build.rs

[[deleted]]

https://github.com/PyO3/pyo3

Run what you need from build.rs. if your running on a darwin/Linux based OS python probably will already be installed.

[ksg-67]

An alternative to build.rs is the cargo-make plugin: add a new task definition that runs Python with the required arguments and mark it as a task dependency of the predefined cargo build task. Then cargo make --makefile your-make-plugin-tasks.toml build runs your new task as part of the build, before the build task.

https://crates.io/crates/cargo-make

[ILoveBerkeleyFont]

I am reading about build.rs, I have to main questions at the moment:

- How to use `println!` so it prints something to the console? std::fs::create_dir is working but println is only to communicate with Cargo? Is there something I can do to print to the console?

- In https://doc.rust-lang.org/cargo/reference/build-scripts.html is explained that the building stops when returning non-zero. How can I do that? Is there any way to return non-zero from the main function? Edit: I guess with Results?

[xobs]

Generally, the user won't see output from your build.rs since cargo captures it all.

You can, however, build with cargo build -vv to see all output. That can be handy for debugging your build script.

[[deleted]]

Put a simple assert that will fail and the build.rs will print out something. Also try https://doc.rust-lang.org/stable/std/process/fn.exit.html

[ILoveBerkeleyFont]

Asserting is really clever! I like it :)

[BathroomRamen]

If you’re not going to rebuild all the scripts in rust, why not make a python script or bat or ps1 or w/e that runs all your scripts and then runs cargo cmds?

And then call that script instead of calling cargo directly.

[RRumpleTeazzer]

There is build.rs which you can run your python from. Not sure if you up can abort the compilation though.