100 exercises to learn Rust

book/src/05_ticket_v2/11_dependencies.md

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+# Dependencies
+
+A package can depend on other packages by listing them in the `[dependencies]` section of its `Cargo.toml` file.  
+The most common way to specify a dependency is by providing its name and version:
+
+```toml
+[dependencies]
+thiserror = "1"
+```
+
+This will add `thiserror` as a dependency to your package, with a **minimum** version of `1.0.0`. 
+`thiserror` will be pulled from [crates.io](https://crates.io), Rust's official package registry.
+When you run `cargo build`, `cargo` will go through a few stages:
+
+- Dependency resolution
+- Downloading the dependencies
+- Compiling your project (your own code and the dependencies)
+
+Dependency resolution is skipped if your project has a `Cargo.lock` file and your manifest files are unchanged.
+A lockfile is automatically generated by `cargo` after a successful round of dependency resolution: it contains 
+the exact versions of all dependencies used in your project, and is used to ensure that the same versions are 
+consistently used across different builds (e.g. in CI). If you're working on a project with multiple developers,
+you should commit the `Cargo.lock` file to your version control system.  
+
+You can use `cargo update` to update the `Cargo.lock` file with the latest (compatible) versions of all your dependencies.
+
+### Path dependencies
+
+You can also specify a dependency using a **path**. This is useful when you're working on multiple local packages.
+
+```toml
+[dependencies]
+my-library = { path = "../my-library" }
+```
+
+The path is relative to the `Cargo.toml` file of the package that's declaring the dependency.
+
+### Other sources
+
+Check out the [Cargo documentation](https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html) for more
+details on where you can get dependencies from and how to specify them in your `Cargo.toml` file.
+
+## Dev dependencies
+
+You can also specify dependencies that are only needed for development—i.e. they only get pulled in when you're
+running `cargo test`.  
+They go in the `[dev-dependencies]` section of your `Cargo.toml` file:
+
+```toml
+[dev-dependencies]
+static_assertions = "1.1.0"
+```
+
+We've been using a few of these throughout the book to shorten our tests.
+
+## References
+
+- The exercise for this section is located in `exercises/05_ticket_v2/11_dependencies`