mirror of
https://github.com/NixOS/nixpkgs.git
synced 2024-11-22 15:03:28 +00:00
fcc95ff817
This allows for correct highlighting and maybe future automatic formatting. The AST was verified to work with nixfmt only.
185 lines
6.0 KiB
Markdown
185 lines
6.0 KiB
Markdown
# Swift {#swift}
|
|
|
|
The Swift compiler is provided by the `swift` package:
|
|
|
|
```sh
|
|
# Compile and link a simple executable.
|
|
nix-shell -p swift --run 'swiftc -' <<< 'print("Hello world!")'
|
|
# Run it!
|
|
./main
|
|
```
|
|
|
|
The `swift` package also provides the `swift` command, with some caveats:
|
|
|
|
- Swift Package Manager (SwiftPM) is packaged separately as `swiftpm`. If you
|
|
need functionality like `swift build`, `swift run`, `swift test`, you must
|
|
also add the `swiftpm` package to your closure.
|
|
- On Darwin, the `swift repl` command requires an Xcode installation. This is
|
|
because it uses the system LLDB debugserver, which has special entitlements.
|
|
|
|
## Module search paths {#ssec-swift-module-search-paths}
|
|
|
|
Like other toolchains in Nixpkgs, the Swift compiler executables are wrapped
|
|
to help Swift find your application's dependencies in the Nix store. These
|
|
wrappers scan the `buildInputs` of your package derivation for specific
|
|
directories where Swift modules are placed by convention, and automatically
|
|
add those directories to the Swift compiler search paths.
|
|
|
|
Swift follows different conventions depending on the platform. The wrappers
|
|
look for the following directories:
|
|
|
|
- On Darwin platforms: `lib/swift/macosx`
|
|
(If not targeting macOS, replace `macosx` with the Xcode platform name.)
|
|
- On other platforms: `lib/swift/linux/x86_64`
|
|
(Where `linux` and `x86_64` are from lowercase `uname -sm`.)
|
|
- For convenience, Nixpkgs also adds `lib/swift` to the search path.
|
|
This can save a bit of work packaging Swift modules, because many Nix builds
|
|
will produce output for just one target any way.
|
|
|
|
## Core libraries {#ssec-swift-core-libraries}
|
|
|
|
In addition to the standard library, the Swift toolchain contains some
|
|
additional 'core libraries' that, on Apple platforms, are normally distributed
|
|
as part of the OS or Xcode. These are packaged separately in Nixpkgs, and can
|
|
be found (for use in `buildInputs`) as:
|
|
|
|
- `swiftPackages.Dispatch`
|
|
- `swiftPackages.Foundation`
|
|
- `swiftPackages.XCTest`
|
|
|
|
## Packaging with SwiftPM {#ssec-swift-packaging-with-swiftpm}
|
|
|
|
Nixpkgs includes a small helper `swiftpm2nix` that can fetch your SwiftPM
|
|
dependencies for you, when you need to write a Nix expression to package your
|
|
application.
|
|
|
|
The first step is to run the generator:
|
|
|
|
```sh
|
|
cd /path/to/my/project
|
|
# Enter a Nix shell with the required tools.
|
|
nix-shell -p swift swiftpm swiftpm2nix
|
|
# First, make sure the workspace is up-to-date.
|
|
swift package resolve
|
|
# Now generate the Nix code.
|
|
swiftpm2nix
|
|
```
|
|
|
|
This produces some files in a directory `nix`, which will be part of your Nix
|
|
expression. The next step is to write that expression:
|
|
|
|
```nix
|
|
{ stdenv, swift, swiftpm, swiftpm2nix, fetchFromGitHub }:
|
|
|
|
let
|
|
# Pass the generated files to the helper.
|
|
generated = swiftpm2nix.helpers ./nix;
|
|
in
|
|
|
|
stdenv.mkDerivation rec {
|
|
pname = "myproject";
|
|
version = "0.0.0";
|
|
|
|
src = fetchFromGitHub {
|
|
owner = "nixos";
|
|
repo = pname;
|
|
rev = version;
|
|
hash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
|
|
};
|
|
|
|
# Including SwiftPM as a nativeBuildInput provides a buildPhase for you.
|
|
# This by default performs a release build using SwiftPM, essentially:
|
|
# swift build -c release
|
|
nativeBuildInputs = [ swift swiftpm ];
|
|
|
|
# The helper provides a configure snippet that will prepare all dependencies
|
|
# in the correct place, where SwiftPM expects them.
|
|
configurePhase = generated.configure;
|
|
|
|
installPhase = ''
|
|
# This is a special function that invokes swiftpm to find the location
|
|
# of the binaries it produced.
|
|
binPath="$(swiftpmBinPath)"
|
|
# Now perform any installation steps.
|
|
mkdir -p $out/bin
|
|
cp $binPath/myproject $out/bin/
|
|
'';
|
|
}
|
|
```
|
|
|
|
### Custom build flags {#ssec-swiftpm-custom-build-flags}
|
|
|
|
If you'd like to build a different configuration than `release`:
|
|
|
|
```nix
|
|
{
|
|
swiftpmBuildConfig = "debug";
|
|
}
|
|
```
|
|
|
|
It is also possible to provide additional flags to `swift build`:
|
|
|
|
```nix
|
|
{
|
|
swiftpmFlags = [ "--disable-dead-strip" ];
|
|
}
|
|
```
|
|
|
|
The default `buildPhase` already passes `-j` for parallel building.
|
|
|
|
If these two customization options are insufficient, provide your own
|
|
`buildPhase` that invokes `swift build`.
|
|
|
|
### Running tests {#ssec-swiftpm-running-tests}
|
|
|
|
Including `swiftpm` in your `nativeBuildInputs` also provides a default
|
|
`checkPhase`, but it must be enabled with:
|
|
|
|
```nix
|
|
{
|
|
doCheck = true;
|
|
}
|
|
```
|
|
|
|
This essentially runs: `swift test -c release`
|
|
|
|
### Patching dependencies {#ssec-swiftpm-patching-dependencies}
|
|
|
|
In some cases, it may be necessary to patch a SwiftPM dependency. SwiftPM
|
|
dependencies are located in `.build/checkouts`, but the `swiftpm2nix` helper
|
|
provides these as symlinks to read-only `/nix/store` paths. In order to patch
|
|
them, we need to make them writable.
|
|
|
|
A special function `swiftpmMakeMutable` is available to replace the symlink
|
|
with a writable copy:
|
|
|
|
```nix
|
|
{
|
|
configurePhase = generated.configure ++ ''
|
|
# Replace the dependency symlink with a writable copy.
|
|
swiftpmMakeMutable swift-crypto
|
|
# Now apply a patch.
|
|
patch -p1 -d .build/checkouts/swift-crypto -i ${./some-fix.patch}
|
|
'';
|
|
}
|
|
```
|
|
|
|
## Considerations for custom build tools {#ssec-swift-considerations-for-custom-build-tools}
|
|
|
|
### Linking the standard library {#ssec-swift-linking-the-standard-library}
|
|
|
|
The `swift` package has a separate `lib` output containing just the Swift
|
|
standard library, to prevent Swift applications needing a dependency on the
|
|
full Swift compiler at run-time. Linking with the Nixpkgs Swift toolchain
|
|
already ensures binaries correctly reference the `lib` output.
|
|
|
|
Sometimes, Swift is used only to compile part of a mixed codebase, and the
|
|
link step is manual. Custom build tools often locate the standard library
|
|
relative to the `swift` compiler executable, and while the result will work,
|
|
when this path ends up in the binary, it will have the Swift compiler as an
|
|
unintended dependency.
|
|
|
|
In this case, you should investigate how your build process discovers the
|
|
standard library, and override the path. The correct path will be something
|
|
like: `"${swift.swift.lib}/${swift.swiftModuleSubdir}"`
|