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Formatter (#51)

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Enforce consistent formatting use `dprint`
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Luca Palmieri
2024-05-24 17:00:03 +02:00
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book/src/05_ticket_v2/10_packages.md
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# Libraries and binaries
It took a bit of code to implement the `Error` trait for `TicketNewError`, didn't it?
It took a bit of code to implement the `Error` trait for `TicketNewError`, didn't it?\
A manual `Display` implementation, plus an `Error` impl block.
We can remove some of the boilerplate by using [`thiserror`](https://docs.rs/thiserror/latest/thiserror/),
a Rust crate that provides a **procedural macro** to simplify the creation of custom error types.
But we're getting ahead of ourselves: `thiserror` is a third-party crate, it'd be our first dependency!
We can remove some of the boilerplate by using [`thiserror`](https://docs.rs/thiserror/latest/thiserror/),
a Rust crate that provides a **procedural macro** to simplify the creation of custom error types.\
But we're getting ahead of ourselves: `thiserror` is a third-party crate, it'd be our first dependency!
Let's take a step back to talk about Rust's packaging system before we dive into dependencies.
## What is a package?
A Rust package is defined by the `[package]` section in a `Cargo.toml` file, also known as its **manifest**.
A Rust package is defined by the `[package]` section in a `Cargo.toml` file, also known as its **manifest**.
Within `[package]` you can set the package's metadata, such as its name and version.
Go check the `Cargo.toml` file in the directory of this section's exercise!
## What is a crate?
Inside a package, you can have one or more **crates**, also known as **targets**.
Inside a package, you can have one or more **crates**, also known as **targets**.\
The two most common crate types are **binary crates** and **library crates**.
### Binaries
A binary is a program that can be compiled to an **executable file**.
A binary is a program that can be compiled to an **executable file**.\
It must include a function named `main`—the program's entry point. `main` is invoked when the program is executed.
### Libraries
Libraries, on the other hand, are not executable on their own. You can't _run_ a library,
but you can _import its code_ from another package that depends on it.
A library groups together code (i.e. functions, types, etc.) that can be leveraged by other packages as a **dependency**.
Libraries, on the other hand, are not executable on their own. You can't _run_ a library,
but you can _import its code_ from another package that depends on it.\
A library groups together code (i.e. functions, types, etc.) that can be leveraged by other packages as a **dependency**.
All the exercises you've solved so far have been structured as libraries, with a test suite attached to them.
@@ -55,7 +55,7 @@ You can use `cargo` to scaffold a new package:
cargo new my-binary
```
This will create a new folder, `my-binary`, containing a new Rust package with the same name and a single
This will create a new folder, `my-binary`, containing a new Rust package with the same name and a single
binary crate inside. If you want to create a library crate instead, you can use the `--lib` flag:
```bash