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diff --git a/README.md b/README.md new file mode 100644 index 000000000000..489cf128173f --- /dev/null +++ b/README.md @@ -0,0 +1,139 @@ +buildGo.nix +=========== + +This is an alternative [Nix][] build system for [Go][]. It supports building Go +libraries and programs, and even automatically generating Protobuf & gRPC +libraries. + +*Note:* This will probably end up being folded into [Nixery][]. + +## Background + +Most language-specific Nix tooling outsources the build to existing +language-specific build tooling, which essentially means that Nix ends up being +a wrapper around all sorts of external build systems. + +However, systems like [Bazel][] take an alternative approach in which the +compiler is invoked directly and the composition of programs and libraries stays +within a single homogeneous build system. + +Users don't need to learn per-language build systems and especially for +companies with large monorepo-setups ([like Google][]) this has huge +productivity impact. + +This project is an attempt to prove that Nix can be used in a similar style to +build software directly, rather than shelling out to other build systems. + +## Example + +Given a program layout like this: + +``` +. +├── lib <-- some library component +│ ├── bar.go +│ └── foo.go +├── api.proto <-- gRPC API definition +├── main.go <-- program implementation +└── default.nix <-- build instructions +``` + +The contents of `default.nix` could look like this: + +```nix +{ buildGo }: + +let + api = buildGo.grpc { + name = "someapi"; + proto = ./api.proto; + }; + + lib = buildGo.package { + name = "somelib"; + srcs = [ + ./lib/bar.go + ./lib/foo.go + ]; + }; +in buildGo.program { + name = "my-program"; + deps = [ api lib ]; + + srcs = [ + ./main.go + ]; +} +``` + +(If you don't know how to read Nix, check out [nix-1p][]) + +## Usage + +`buildGo` exposes five different functions: + +* `buildGo.program`: Build a Go binary out of the specified source files. + + | parameter | type | use | required? | + |-----------|-------------------------|------------------------------------------------|-----------| + | `name` | `string` | Name of the program (and resulting executable) | yes | + | `srcs` | `list<path>` | List of paths to source files | yes | + | `deps` | `list<drv>` | List of dependencies (i.e. other Go libraries) | no | + | `x_defs` | `attrs<string, string>` | Attribute set of linker vars (i.e. `-X`-flags) | no | + +* `buildGo.package`: Build a Go library out of the specified source files. + + | parameter | type | use | required? | + |-----------|--------------|------------------------------------------------|-----------| + | `name` | `string` | Name of the library (and resulting executable) | yes | + | `srcs` | `list<path>` | List of paths to source files | yes | + | `deps` | `list<drv>` | List of dependencies (i.e. other Go libraries) | no | + | `path` | `string` | Go import path for the resulting library | no | + +* `buildGo.external`: Build a Go library or program using standard `go` tooling. + + This exists for compatibility with complex external dependencies. In theory it + is possible to write `buildGo.package` specifications for each subpackage of + an external dependency, but it is often cumbersome to do so. + + | parameter | type | use | required? | + |-----------|----------------|------------------------------------------------|-----------| + | `path` | `string` | Go import path for the resulting library | yes | + | `src` | `path` | Path to the source **directory** | yes | + | `deps` | `list<drv>` | List of dependencies (i.e. other Go libraries) | no | + | `srcOnly` | `bool` | Only copy sources, do not perform a build. | no | + | `targets` | `list<string>` | Sub-packages to build (defaults to all) | no | + + For some examples of how `buildGo.external` is used, check out + [`proto.nix`](./proto.nix). + +* `buildGo.proto`: Build a Go library out of the specified Protobuf definition. + + | parameter | type | use | required? | + |-------------|-------------|--------------------------------------------------|-----------| + | `name` | `string` | Name for the resulting library | yes | + | `proto` | `path` | Path to the Protobuf definition file | yes | + | `path` | `string` | Import path for the resulting Go library | no | + | `extraDeps` | `list<drv>` | Additional Go dependencies to add to the library | no | + +* `buildGo.grpc`: Build a Go library out of the specified gRPC definition. + + The parameters are identical to `buildGo.proto`. + +## Current status + +This project is work-in-progress. Crucially it is lacking the following features: + +* feature flag parity with Bazel's Go rules +* documentation building +* test execution + +There are still some open questions around how to structure some of those +features in Nix. + +[Nix]: https://nixos.org/nix/ +[Go]: https://golang.org/ +[Nixery]: https://github.com/google/nixery +[Bazel]: https://bazel.build/ +[like Google]: https://ai.google/research/pubs/pub45424 +[nix-1p]: https://github.com/tazjin/nix-1p |