```nix
rustPlatform.buildRustPackage {
  # ...
  buildType = "debug";
}
```

In this scenario, the `checkPhase` will be ran in `debug` mode as well.

### Custom `build`/`install`-procedures {#custom-buildinstall-procedures}

Some packages may use custom scripts for building/installing, e.g. with a `Makefile`.
In these cases, it's recommended to override the `buildPhase`/`installPhase`/`checkPhase`.

Otherwise, some steps may fail because of the modified directory structure of `target/`.

### Building a crate with an absent or out-of-date Cargo.lock file {#building-a-crate-with-an-absent-or-out-of-date-cargo.lock-file}

`buildRustPackage` needs a `Cargo.lock` file to get all dependencies in the
source code in a reproducible way. If it is missing or out-of-date one can use
the `cargoPatches` attribute to update or add it.

```nix
rustPlatform.buildRustPackage {
  # ...
  cargoPatches = [
    # a patch file to add/update Cargo.lock in the source code
    ./add-Cargo.lock.patch
  ];
}
```

### Compiling non-Rust packages that include Rust code {#compiling-non-rust-packages-that-include-rust-code}

Several non-Rust packages incorporate Rust code for performance- or
security-sensitive parts. `rustPlatform` exposes several functions and
hooks that can be used to integrate Cargo in non-Rust packages.

#### Vendoring of dependencies {#vendoring-of-dependencies}

Since network access is not allowed in sandboxed builds, Rust crate
dependencies need to be retrieved using a fetcher. `rustPlatform`
provides the `fetchCargoVendor` fetcher, which vendors all
dependencies of a crate. For example, given a source path `src`
containing `Cargo.toml` and `Cargo.lock`, `fetchCargoVendor`
can be used as follows:

```nix
{
  cargoDeps = rustPlatform.fetchCargoVendor {
    inherit src;
    hash = "sha256-BoHIN/519Top1NUBjpB/oEMqi86Omt3zTQcXFWqrek0=";
  };
}
```

The `src` attribute is required, as well as a hash specified through
one of the `hash` attribute. The following optional attributes can
also be used:

* `name`: the name that is used for the dependencies tarball.  If
  `name` is not specified, then the name `cargo-deps` will be used.
* `sourceRoot`: when the `Cargo.lock`/`Cargo.toml` are in a
  subdirectory, `sourceRoot` specifies the relative path to these
  files.
* `patches`: patches to apply before vendoring. This is useful when
  the `Cargo.lock`/`Cargo.toml` files need to be patched before
  vendoring.

If a `Cargo.lock` file is available, you can alternatively use the
`importCargoLock` function. In contrast to `fetchCargoVendor`, this
function does not require a hash (unless git dependencies are used)
and fetches every dependency as a separate fixed-output derivation.
`importCargoLock` can be used as follows:

```nix
{
  cargoDeps = rustPlatform.importCargoLock {
    lockFile = ./Cargo.lock;
  };
}
```

If the `Cargo.lock` file includes git dependencies, then their output
hashes need to be specified since they are not available through the
lock file. For example:

```nix
{
  cargoDeps = rustPlatform.importCargoLock {
    lockFile = ./Cargo.lock;
    outputHashes = {
      "rand-0.8.3" = "0ya2hia3cn31qa8894s3av2s8j5bjwb6yq92k0jsnlx7jid0jwqa";
    };
  };
}
```

If you do not specify an output hash for a git dependency, building
`cargoDeps` will fail and inform you of which crate needs to be
added. To find the correct hash, you can first use `lib.fakeSha256` or
`lib.fakeHash` as a stub hash. Building `cargoDeps` will then inform
you of the correct hash.

#### Hooks {#hooks}

`rustPlatform` provides the following hooks to automate Cargo builds:

* `cargoSetupHook`: configure Cargo to use dependencies vendored
  through `fetchCargoVendor` or `importCargoLock`. This hook uses the
  `cargoDeps` environment variable to find the vendored
  dependencies. If a project already vendors its dependencies, the
  variable `cargoVendorDir` can be used instead. When the
  `Cargo.toml`/`Cargo.lock` files are not in `sourceRoot`, then the
  optional `cargoRoot` is used to specify the Cargo root directory