feat: Check in buildGo with program & package builders

buildGo.nix

@@ -0,0 +1,70 @@
+# Copyright 2019 Google LLC.
+# SPDX-License-Identifier: Apache-2.0
+#
+# buildGo provides Nix functions to build Go packages in the style of Bazel's
+# rules_go.
+
+{ pkgs ? import <nixpkgs> {}
+, ... }:
+
+let
+  inherit (builtins)
+    attrNames
+    baseNameOf
+    elemAt
+    filter
+    map
+    match
+    readDir;
+
+  inherit (pkgs) lib go runCommand;
+
+  # Helpers for low-level Go compiler invocations
+  spaceOut = lib.concatStringsSep " ";
+
+  includeDepSrc = dep: "-I ${dep}";
+  includeSources = deps: spaceOut (map includeDepSrc deps);
+
+  includeDepLib = dep: "-L ${dep}";
+  includeLibs = deps: spaceOut (map includeDepLib deps);
+
+  srcBasename = src: elemAt (match "([a-z0-9]{32}\-)?(.*\.go)" (baseNameOf src)) 1;
+  srcCopy = path: src: "cp ${src} $out/${path}/${srcBasename src}";
+  srcList = path: srcs: lib.concatStringsSep "\n" (map (srcCopy path) srcs);
+
+  isGoFile = f: (match ".*\.go" f) != null;
+  isGoTest = f: (match ".*_test\.go" f) != null;
+  goFileFilter = k: v: (v == "regular") && (isGoFile k) && (!isGoTest k);
+  goFilesIn = dir:
+    let files = readDir dir;
+        goFiles = filter (f: goFileFilter f files."${f}") (attrNames files);
+    in map (f: dir + "/" + f) goFiles;
+
+  allDeps = deps: lib.unique (lib.flatten (deps ++ (map (d: d.goDeps) deps)));
+
+  # High-level build functions
+
+  # Build a Go program out of the specified files and dependencies.
+  program = { name, srcs, deps ? [] }:
+  let uniqueDeps = allDeps deps;
+  in runCommand name {} ''
+    ${go}/bin/go tool compile -o ${name}.a -trimpath=$PWD -trimpath=${go} ${includeSources uniqueDeps} ${spaceOut srcs}
+    mkdir -p $out/bin
+    ${go}/bin/go tool link -o $out/bin/${name} -buildid nix ${includeLibs uniqueDeps} ${name}.a
+  '';
+
+  # Build a Go library assembled out of the specified files.
+  #
+  # This outputs both the sources and compiled binary, as both are
+  # needed when downstream packages depend on it.
+  package = { name, srcs, deps ? [], path ? name }:
+  let uniqueDeps = allDeps deps;
+  in (runCommand "golib-${name}" {} ''
+    mkdir -p $out/${path}
+    ${srcList path (map (s: "${s}") srcs)}
+    ${go}/bin/go tool compile -o $out/${path}.a -trimpath=$PWD -trimpath=${go} -p ${path} ${includeSources uniqueDeps} ${spaceOut srcs}
+  '') // { goDeps = uniqueDeps; };
+in {
+  # Only the high-level builder functions are exposed
+  inherit program package;
+}