For those who don’t know, rust-analyzer is the main rust LSP (Language Server Protocol). So super handy! Here’s their homepage: https://rust-analyzer.github.io/

I wanted to have it running for little all the programs and tests I’d write and run while going through “The Book” and have settled on a setup I thought I’d share.

The main problem I encountered is that having R-A run on a single file isn’t really a thing. It seems it kinda is but I couldn’t get it working and it seemed to be a pain anyway. Plus I wanted to be able to use both cargo projects/crates and little test programs/functions simultaneously from a single workspace in my text editor dedicated to working through The Book.

My solution

at the moment

What I settled on was:

• Running multiple cargo projects under a single instance of rust-analyzer running in a single workspace in my editor
• Organising simple test programs as specific functions in a single cargo project.
  • So far, I’m thinking of organising these thematically specifical cargo projects. So I’ve got one called “borrow_checker” for all borrow checker and ownership toy examples.
  • These specific functions can get called from a single main() if helpful/necessary.

EG directory structure:

the_book/
 ├──  Cargo.lock
 ├──  Cargo.toml
 ├──  guessing_game/
 │  ├──  .gitignore
 │  ├──  Cargo.lock
 │  ├──  Cargo.toml
 │  ├──  src/
 │  └──  target/
 ├──  hello_cargo/
 │  ├──  .gitignore
 │  ├──  Cargo.lock
 │  ├──  Cargo.toml
 │  ├──  src/
 │  └──  target/
 ├──  misc_play/
 │  └──  borrow_checker/
 │     ├──  .gitignore
 │     ├──  Cargo.lock
 │     ├──  Cargo.toml
 │     ├──  src/
 │     └──  target/
 └──  target/
    ├──  .rustc_info.json
    ├──  CACHEDIR.TAG
    └──  debug/

Basically everything inside the_book/ is its own cargo project.

And inside misc_play/borrow_checker/src/ is a typical main.rs with multiple functions testing or toying with something I was trying to understand … and hopefully use the LSP to help me with.

Getting this to work

So that’s the structure. But getting it to work requires a little trick. It requires using a Cargo Workspace.

In this case, it’s a matter of adding a Cargo.toml file at the top level (ie, the_book/Cargo.toml) with the following:

[workspace]

resolver = "2"
edition = "2021"

members = [
	"guessing_game",
	"hello_cargo",
	"misc_play/borrow_checker"
]

Here, members is clearly listing each of the projects or libraries. And I added the resolver and edition keys to silence a cargo warning about incompatible resolvers (which I don’t know anything about).

With this file, when at the top level, one can run cargo build to build all of the projects/packages. Or, cargo build -p SPECIFIC_MEMBER to build only a specific project/package. Meanwhile, rust-analyzer seems happy to work on any file from any of these projects in a single editor workspace.

There’s a section in The Book on cargo workspaces: https://doc.rust-lang.org/book/ch14-03-cargo-workspaces.html (where this feature is about much more than just getting rust-analyzer to work with my preferred directory structure!)

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Anyone else have thoughts on how best to structure your code and setup for working through something like The Book or any other materials for that matter?