We’re going to create a new Rust project with a binary crate. I’ve called mine scaffold but you can name it whatever you want, as long as cargo accepts the name. By default this will be the name of the final program that we run on the CLI.
cargo new scaffold
Inside of our new directory, we have a new Cargo.toml detailing our package as well as the edition of Rust we’re using.
❯ cat Cargo.toml
[package]
name = "scaffold"
version = "0.1.0"
edition = "2021"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies]
as well as a src/main.rs which we can run with cargo run for the first time.
❯ cargo run
Compiling scaffold v0.1.0 (/rust-adventure/scaffold)
Finished dev [unoptimized + debuginfo] target(s) in 0.69s
Running `target/debug/scaffold`
Hello, world!
This creates a target directory that contains our build artifacts, as well as a Cargo.lock file which would include dependency information if we had any.
❯ cat Cargo.lock
# This file is automatically @generated by Cargo.
# It is not intended for manual editing.
version = 3
[[package]]
name = "scaffold"
version = "0.1.0"
There is also a .gitignore file that ignores the target/ directory, as we don’t want to commit our build artifacts to git.
Adding Clap with the derive feature
We know we’re going to use the clap crate with the derive cargo feature. We’ll cover what the derive feature is doing for us in the next lesson.
Use cargo add, which is a built-in feature of cargo, to add clap to our project. The -F flag is used to enable cargo features, in this case the derive feature. Other features and whether or not they’re enabled show in the results.
❯ cargo add clap -F derive
Updating crates.io index
Adding clap v4.3.19 to dependencies.
Features:
+ color
+ derive
+ error-context
+ help
+ std
+ suggestions
+ usage
- cargo
- debug
- deprecated
- env
- string
- unicode
- unstable-doc
- unstable-styles
- unstable-v5
- wrap_help
Updating crates.io index
A cargo feature is used to conditionally add dependencies, or conditionally add swaths of code for a crate.
In this case, the derive feature enables the code that powers a set of attribute macros that we’ll explore in the next lesson.
clap then appears in the dependencies array of our Cargo.toml, with the version specified and the derive feature in the features list.
[package]
name = "scaffold"
version = "0.1.0"
edition = "2021"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies]
clap = { version = "4.3.19", features = ["derive"] }
The Cargo.lock now also contains a whole host of detail about the transitive dependencies clap relies on.
# This file is automatically @generated by Cargo.
# It is not intended for manual editing.
version = 3
[[package]]
name = "anstream"
version = "0.3.2"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "0ca84f3628370c59db74ee214b3263d58f9aadd9b4fe7e711fd87dc452b7f163"
dependencies = [
"anstyle",
"anstyle-parse",
"anstyle-query",
"anstyle-wincon",
"colorchoice",
"is-terminal",
"utf8parse",
]
...more...
With clap added to our project, we can move on to using it.