476 lines
15 KiB
Markdown
476 lines
15 KiB
Markdown
---
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title: Rust
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author: Matthias Beyer
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date: 2017-03-05
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---
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# Rust
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To install the rust compiler and cargo put
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```
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rustc
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cargo
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```
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into the `environment.systemPackages` or bring them into
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scope with `nix-shell -p rustc cargo`.
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For daily builds (beta and nightly) use either rustup from
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nixpkgs or use the [Rust nightlies
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overlay](#using-the-rust-nightlies-overlay).
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## Compiling Rust applications with Cargo
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Rust applications are packaged by using the `buildRustPackage` helper from `rustPlatform`:
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```
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rustPlatform.buildRustPackage rec {
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pname = "ripgrep";
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version = "11.0.2";
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src = fetchFromGitHub {
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owner = "BurntSushi";
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repo = pname;
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rev = version;
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sha256 = "1iga3320mgi7m853la55xip514a3chqsdi1a1rwv25lr9b1p7vd3";
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};
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cargoSha256 = "17ldqr3asrdcsh4l29m3b5r37r5d0b3npq1lrgjmxb6vlx6a36qh";
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meta = with stdenv.lib; {
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description = "A fast line-oriented regex search tool, similar to ag and ack";
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homepage = "https://github.com/BurntSushi/ripgrep";
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license = licenses.unlicense;
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maintainers = [ maintainers.tailhook ];
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platforms = platforms.all;
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};
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}
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```
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`buildRustPackage` requires a `cargoSha256` attribute which is computed over
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all crate sources of this package. Currently it is obtained by inserting a
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fake checksum into the expression and building the package once. The correct
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checksum can be then take from the failed build.
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Per the instructions in the [Cargo Book](https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html)
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best practices guide, Rust applications should always commit the `Cargo.lock`
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file in git to ensure a reproducible build. However, a few packages do not, and
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Nix depends on this file, so if it missing you can use `cargoPatches` to apply
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it in the `patchPhase`. Consider sending a PR upstream with a note to the
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maintainer describing why it's important to include in the application.
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The fetcher will verify that the `Cargo.lock` file is in sync with the `src`
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attribute, and fail the build if not. It will also will compress the vendor
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directory into a tar.gz archive.
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### Building a crate for a different target
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To build your crate with a different cargo `--target` simply specify the `target` attribute:
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```nix
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pkgs.rustPlatform.buildRustPackage {
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(...)
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target = "x86_64-fortanix-unknown-sgx";
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}
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```
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### Running package tests
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When using `buildRustPackage`, the `checkPhase` is enabled by default and runs
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`cargo test` on the package to build. To make sure that we don't compile the
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sources twice and to actually test the artifacts that will be used after that,
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the tests will be ran in the `release`-mode by default.
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However, in some cases the test-suite of a package doesn't work properly in the
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`release` mode. In that case, the mode for `checkPhase` can be changed like this:
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```nix
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rustPlatform.buildRustPackage {
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/* ... */
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checkType = "debug";
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}
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```
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#### Tests relying on the structure of the `target/`-directory
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Some tests may rely on the structure of the `target/`-directory. Those tests
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are likely to fail since we use `cargo --target` during build. This means that
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the artifacts
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[are stored in `target/<architecture>/release/`](https://doc.rust-lang.org/cargo/guide/build-cache.html)
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rather than `target/release/`.
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This can only be circumvented by patching the affected tests accordingly.
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#### Disabling package-tests
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In some cases it's necessary to disable the tests (which can be done by declaring
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`doCheck = false;`) which is fine in the following cases:
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* If no tests exist, the `checkPhase` should be explicitly disabled to skip
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unnecessary build-steps to speed-up the build.
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* If tests are highly impure (e.g. due to heavy network usage), it's also fine
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disable tests.
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There are obviously some other corner-cases where it's sensible to disable tests,
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those aren't hard-rules, in the end this is a case-by-case decision.
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Please check however if it's possible to disable a problematic subset of the
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test-suite and leave comment which explains why that's needed.
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### Building a package in the `debug` mode
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By default, `buildRustPackage` will use the `release`-mode for building. If a package
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should be built in the `debug`-mode however, it can be configured like this:
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```nix
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rustPlatform.buildRustPackage {
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/* ... */
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buildType = "debug";
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}
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```
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Obviously, the `checkPhase` will be ran in `debug`-mode as well in this case.
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### Custom `build`/`install`-procedures
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Some packages may use custom scripts for building/installing, e.g. with a `Makefile`.
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In that case it's recommended to always override the `build-`/`install-`/`checkPhase`.
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Otherwise, it may be possible that one of the internal steps fails because of the
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modified directory structure of `target/`.
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## Compiling Rust crates using Nix instead of Cargo
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### Simple operation
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When run, `cargo build` produces a file called `Cargo.lock`,
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containing pinned versions of all dependencies. Nixpkgs contains a
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tool called `carnix` (`nix-env -iA nixos.carnix`), which can be used
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to turn a `Cargo.lock` into a Nix expression.
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That Nix expression calls `rustc` directly (hence bypassing Cargo),
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and can be used to compile a crate and all its dependencies. Here is
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an example for a minimal `hello` crate:
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$ cargo new hello
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$ cd hello
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$ cargo build
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Compiling hello v0.1.0 (file:///tmp/hello)
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Finished dev [unoptimized + debuginfo] target(s) in 0.20 secs
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$ carnix -o hello.nix --src ./. Cargo.lock --standalone
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$ nix-build hello.nix -A hello_0_1_0
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Now, the file produced by the call to `carnix`, called `hello.nix`, looks like:
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```
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# Generated by carnix 0.6.5: carnix -o hello.nix --src ./. Cargo.lock --standalone
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{ lib, stdenv, buildRustCrate, fetchgit }:
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let kernel = stdenv.buildPlatform.parsed.kernel.name;
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# ... (content skipped)
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in
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rec {
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hello = f: hello_0_1_0 { features = hello_0_1_0_features { hello_0_1_0 = f; }; };
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hello_0_1_0_ = { dependencies?[], buildDependencies?[], features?[] }: buildRustCrate {
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crateName = "hello";
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version = "0.1.0";
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authors = [ "pe@pijul.org <pe@pijul.org>" ];
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src = ./.;
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inherit dependencies buildDependencies features;
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};
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hello_0_1_0 = { features?(hello_0_1_0_features {}) }: hello_0_1_0_ {};
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hello_0_1_0_features = f: updateFeatures f (rec {
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hello_0_1_0.default = (f.hello_0_1_0.default or true);
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}) [ ];
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}
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```
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In particular, note that the argument given as `--src` is copied
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verbatim to the source. If we look at a more complicated
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dependencies, for instance by adding a single line `libc="*"` to our
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`Cargo.toml`, we first need to run `cargo build` to update the
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`Cargo.lock`. Then, `carnix` needs to be run again, and produces the
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following nix file:
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```
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# Generated by carnix 0.6.5: carnix -o hello.nix --src ./. Cargo.lock --standalone
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{ lib, stdenv, buildRustCrate, fetchgit }:
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let kernel = stdenv.buildPlatform.parsed.kernel.name;
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# ... (content skipped)
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in
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rec {
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hello = f: hello_0_1_0 { features = hello_0_1_0_features { hello_0_1_0 = f; }; };
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hello_0_1_0_ = { dependencies?[], buildDependencies?[], features?[] }: buildRustCrate {
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crateName = "hello";
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version = "0.1.0";
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authors = [ "pe@pijul.org <pe@pijul.org>" ];
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src = ./.;
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inherit dependencies buildDependencies features;
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};
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libc_0_2_36_ = { dependencies?[], buildDependencies?[], features?[] }: buildRustCrate {
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crateName = "libc";
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version = "0.2.36";
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authors = [ "The Rust Project Developers" ];
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sha256 = "01633h4yfqm0s302fm0dlba469bx8y6cs4nqc8bqrmjqxfxn515l";
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inherit dependencies buildDependencies features;
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};
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hello_0_1_0 = { features?(hello_0_1_0_features {}) }: hello_0_1_0_ {
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dependencies = mapFeatures features ([ libc_0_2_36 ]);
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};
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hello_0_1_0_features = f: updateFeatures f (rec {
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hello_0_1_0.default = (f.hello_0_1_0.default or true);
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libc_0_2_36.default = true;
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}) [ libc_0_2_36_features ];
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libc_0_2_36 = { features?(libc_0_2_36_features {}) }: libc_0_2_36_ {
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features = mkFeatures (features.libc_0_2_36 or {});
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};
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libc_0_2_36_features = f: updateFeatures f (rec {
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libc_0_2_36.default = (f.libc_0_2_36.default or true);
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libc_0_2_36.use_std =
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(f.libc_0_2_36.use_std or false) ||
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(f.libc_0_2_36.default or false) ||
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(libc_0_2_36.default or false);
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}) [];
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}
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```
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Here, the `libc` crate has no `src` attribute, so `buildRustCrate`
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will fetch it from [crates.io](https://crates.io). A `sha256`
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attribute is still needed for Nix purity.
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### Handling external dependencies
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Some crates require external libraries. For crates from
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[crates.io](https://crates.io), such libraries can be specified in
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`defaultCrateOverrides` package in nixpkgs itself.
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Starting from that file, one can add more overrides, to add features
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or build inputs by overriding the hello crate in a seperate file.
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```
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with import <nixpkgs> {};
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((import ./hello.nix).hello {}).override {
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crateOverrides = defaultCrateOverrides // {
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hello = attrs: { buildInputs = [ openssl ]; };
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};
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}
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```
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Here, `crateOverrides` is expected to be a attribute set, where the
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key is the crate name without version number and the value a function.
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The function gets all attributes passed to `buildRustCrate` as first
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argument and returns a set that contains all attribute that should be
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overwritten.
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For more complicated cases, such as when parts of the crate's
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derivation depend on the crate's version, the `attrs` argument of
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the override above can be read, as in the following example, which
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patches the derivation:
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```
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with import <nixpkgs> {};
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((import ./hello.nix).hello {}).override {
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crateOverrides = defaultCrateOverrides // {
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hello = attrs: lib.optionalAttrs (lib.versionAtLeast attrs.version "1.0") {
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postPatch = ''
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substituteInPlace lib/zoneinfo.rs \
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--replace "/usr/share/zoneinfo" "${tzdata}/share/zoneinfo"
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'';
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};
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};
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}
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```
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Another situation is when we want to override a nested
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dependency. This actually works in the exact same way, since the
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`crateOverrides` parameter is forwarded to the crate's
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dependencies. For instance, to override the build inputs for crate
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`libc` in the example above, where `libc` is a dependency of the main
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crate, we could do:
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```
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with import <nixpkgs> {};
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((import hello.nix).hello {}).override {
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crateOverrides = defaultCrateOverrides // {
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libc = attrs: { buildInputs = []; };
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};
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}
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```
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### Options and phases configuration
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Actually, the overrides introduced in the previous section are more
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general. A number of other parameters can be overridden:
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- The version of rustc used to compile the crate:
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```
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(hello {}).override { rust = pkgs.rust; };
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```
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- Whether to build in release mode or debug mode (release mode by
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default):
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```
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(hello {}).override { release = false; };
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```
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- Whether to print the commands sent to rustc when building
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(equivalent to `--verbose` in cargo:
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```
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(hello {}).override { verbose = false; };
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```
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- Extra arguments to be passed to `rustc`:
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```
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(hello {}).override { extraRustcOpts = "-Z debuginfo=2"; };
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```
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- Phases, just like in any other derivation, can be specified using
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the following attributes: `preUnpack`, `postUnpack`, `prePatch`,
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`patches`, `postPatch`, `preConfigure` (in the case of a Rust crate,
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this is run before calling the "build" script), `postConfigure`
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(after the "build" script),`preBuild`, `postBuild`, `preInstall` and
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`postInstall`. As an example, here is how to create a new module
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before running the build script:
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```
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(hello {}).override {
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preConfigure = ''
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echo "pub const PATH=\"${hi.out}\";" >> src/path.rs"
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'';
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};
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```
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### Features
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One can also supply features switches. For example, if we want to
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compile `diesel_cli` only with the `postgres` feature, and no default
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features, we would write:
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```
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(callPackage ./diesel.nix {}).diesel {
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default = false;
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postgres = true;
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}
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```
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Where `diesel.nix` is the file generated by Carnix, as explained above.
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## Setting Up `nix-shell`
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Oftentimes you want to develop code from within `nix-shell`. Unfortunately
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`buildRustCrate` does not support common `nix-shell` operations directly
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(see [this issue](https://github.com/NixOS/nixpkgs/issues/37945))
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so we will use `stdenv.mkDerivation` instead.
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Using the example `hello` project above, we want to do the following:
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- Have access to `cargo` and `rustc`
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- Have the `openssl` library available to a crate through it's _normal_
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compilation mechanism (`pkg-config`).
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A typical `shell.nix` might look like:
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```
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with import <nixpkgs> {};
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stdenv.mkDerivation {
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name = "rust-env";
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nativeBuildInputs = [
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rustc cargo
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# Example Build-time Additional Dependencies
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pkgconfig
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];
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buildInputs = [
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# Example Run-time Additional Dependencies
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openssl
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];
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# Set Environment Variables
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RUST_BACKTRACE = 1;
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}
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```
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You should now be able to run the following:
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```
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$ nix-shell --pure
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$ cargo build
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$ cargo test
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```
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### Controlling Rust Version Inside `nix-shell`
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To control your rust version (i.e. use nightly) from within `shell.nix` (or
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other nix expressions) you can use the following `shell.nix`
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```
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# Latest Nightly
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with import <nixpkgs> {};
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let src = fetchFromGitHub {
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owner = "mozilla";
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repo = "nixpkgs-mozilla";
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# commit from: 2019-05-15
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rev = "9f35c4b09fd44a77227e79ff0c1b4b6a69dff533";
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sha256 = "18h0nvh55b5an4gmlgfbvwbyqj91bklf1zymis6lbdh75571qaz0";
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};
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in
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with import "${src.out}/rust-overlay.nix" pkgs pkgs;
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stdenv.mkDerivation {
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name = "rust-env";
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buildInputs = [
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# Note: to use use stable, just replace `nightly` with `stable`
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latest.rustChannels.nightly.rust
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# Add some extra dependencies from `pkgs`
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pkgconfig openssl
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];
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# Set Environment Variables
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RUST_BACKTRACE = 1;
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}
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```
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Now run:
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```
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$ rustc --version
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rustc 1.26.0-nightly (188e693b3 2018-03-26)
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```
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To see that you are using nightly.
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## Using the Rust nightlies overlay
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Mozilla provides an overlay for nixpkgs to bring a nightly version of Rust into scope.
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This overlay can _also_ be used to install recent unstable or stable versions
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of Rust, if desired.
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To use this overlay, clone
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[nixpkgs-mozilla](https://github.com/mozilla/nixpkgs-mozilla),
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and create a symbolic link to the file
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[rust-overlay.nix](https://github.com/mozilla/nixpkgs-mozilla/blob/master/rust-overlay.nix)
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in the `~/.config/nixpkgs/overlays` directory.
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$ git clone https://github.com/mozilla/nixpkgs-mozilla.git
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$ mkdir -p ~/.config/nixpkgs/overlays
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$ ln -s $(pwd)/nixpkgs-mozilla/rust-overlay.nix ~/.config/nixpkgs/overlays/rust-overlay.nix
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The latest version can be installed with the following command:
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$ nix-env -Ai nixos.latest.rustChannels.stable.rust
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Or using the attribute with nix-shell:
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$ nix-shell -p nixos.latest.rustChannels.stable.rust
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To install the beta or nightly channel, "stable" should be substituted by
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"nightly" or "beta", or
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use the function provided by this overlay to pull a version based on a
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build date.
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The overlay automatically updates itself as it uses the same source as
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[rustup](https://www.rustup.rs/).
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