Dependencies

Cargo includes dependency management, as opposed to having to integrate vcpkg, conan, etc.

We've used dependencies already to link a library from the same workspace. Adding other dependencies follows a similar pattern.

Finding Dependencies

You can search the available public crate repo (crates.io) with cargo search <term>. For example, searching for serde (a crate we'll be using later) gives the following result:

$ cargo search serde
serde = "1.0.193"                       # A generic serialization/deserialization framework
sideko_postman_api = "1.0.0"            # Rust API bindings - spostman_api
discord_typed_interactions = "0.1.0"    # suppose you're working with discord slash commands and you want statically typed reques…
serde_json_experimental = "0.0.0"       # A JSON serialization file format
serde_valid = "0.16.3"                  # JSON Schema based validation tool using with serde.
alt_serde_json = "1.0.61"               # A JSON serialization file format
serde_json = "1.0.108"                  # A JSON serialization file format
serde_jsonc = "1.0.108"                 # A JSON serialization file format
serde_partiql = "1.1.65"                # A PartiQL data model serialization file format
deserr = "0.6.1"                        # Deserialization library with focus on error handling
... and 5301 crates more (use --limit N to see more)

It's often more productive to use Google or crates.io directly to see what's available. The number of crates is growing rapidly, and they are of varied quality. It's worth doing a little research before picking one!

Adding Crates to Your Project

You can either use cargo search and find the appropriate information and add a crate by hand to your Cargo.toml:

[dependencies]
serde = "1.0.193"

Or you can use cargo add serde to add the crate to your Cargo.toml.

Feature Flags

Rust crates can have feature flags that enable functionality. For example, when using serde most of the time you will also use the derive feature flag to enable #[derive(Serialize)] type macros that make life much easier.

You'd either edit Cargo.toml to read:

[dependencies]
serde = { version = "1.0.193", features = [ "derive" ] }

Or run cargo add serde -F derive.

Updating Crates

You can update to the latest versions with cargo update.

"Vendoring" Crates

For repeatable builds (or working offline), you can run cargo vendor and follow the instructions. It downloads the source for all of your dependencies, and provides a snippet to add to your Cargo.toml to use the local versions.

Other Crate Sources

You can connect a crate via a Git repo (and optionally add a branch= specifier):

[dependencies]
bracket-lib = { git = "https://github.com/amethyst/bracket-lib.git" }

You can use also use a path, like we did for libraries.

Viewing dependencies

cargo tree will show you all of your dependencies for a project, nested with their dependencies. It can get a bit excessive, sometimes!

Cargo.lock

Cargo maintains a file named Cargo.lock. The Rust project recommend not including this in your git repo---but many people recommend the opposite!

Cargo.lock lists exact versions of every crate that was used by the entire build process. If you have the same Cargo.lock, you will download the exact same files (if they haven't been withdrawn).