Cargo Workspaces

# Cargo Workspaces

---
## Cargo Workspaces

Allow you to split your project into several packages

* further encourages modularity
* develop multiple applications and libraries in a single tree
* synchronized dependency management, release process, etc.
* a way to parallelize compilation and speed up builds
* **your internal projects should likely be workspaces** even if you don't use monorepos

---
## Anatomy of Rust Workspace

```text
my-app/
├── Cargo.toml   # a special workspace file
├── Cargo.lock   # notice that Cargo produces a common lockfile for all packages
├── packages/      # can use any directory structure
│   ├── main-app/
│   │   ├── Cargo.toml
│   │   └── src/
│   │       └── main.rs
│   ├── admin-app/
│   │   └── ...
│   ├── common-data-model/
│   │   ├── Cargo.toml
│   │   └── src/
│   │       └── lib.rs
│   ├── useful-macros
│   ├── service-a
│   ├── service-b
│   └── ...
└── tools/       # packages don't have to be in the same directory
    ├── release-bot/
    │   ├── Cargo.toml
    │   └── src/
    │       └── main.rs
    ├── data-migration-scripts/
    │   ├── Cargo.toml
    │   └── src/
    │       └── main.rs
    └── ...
```

---
## Workspace Cargo.toml

```toml
[workspace]
resolver = "2"
members = ["packages/*", "tools/*"]

[dependencies]
thiserror = "1.0.39"
...
```

using wildcards for members is very handy when you want to add new member packages, split packages, etc.

---
## Cargo.toml for a workspace member

```toml
[package]
name = "main-app"

[dependencies]
thiserror = { workspace = true }
service-a = { path = "../service-a" }
...
```

---
## Cargo commands for workspaces

* `cargo run --bin main-app`
* `cargo test -p service-a`

---
## Creating a workspace

```sh
#!/usr/bin/env bash
function nw() {
  local name="$1"
  local work_dir="$PWD"
  mkdir -p "$work_dir/$name/packages"
  git init -q "$work_dir/$name"
  cat > "$work_dir/$name/Cargo.toml" << EOF
[workspace]
resolver = "2"
members = ["packages/*"]

[workspace.dependencies]
EOF
  cat > "$work_dir/$name/.gitignore" << EOF
target
EOF
  code "$work_dir/$name"
}
```

Example:
```bash
nw spaceship
cargo new --lib spaceship/packages/fuel-control
```