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diff --git a/nix/buildGo/default.nix b/nix/buildGo/default.nix
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+# 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
+    dirOf
+    elemAt
+    filter
+    listToAttrs
+    map
+    match
+    readDir
+    replaceStrings
+    toString;
+
+  inherit (pkgs) lib go runCommand fetchFromGitHub protobuf symlinkJoin;
+
+  # 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);
+
+  allDeps = deps: lib.unique (lib.flatten (deps ++ (map (d: d.goDeps) deps)));
+
+  xFlags = x_defs: spaceOut (map (k: "-X ${k}=${x_defs."${k}"}") (attrNames x_defs));
+
+  pathToName = p: replaceStrings ["/"] ["_"] (toString p);
+
+  # Add an `overrideGo` attribute to a function result that works
+  # similar to `overrideAttrs`, but is used specifically for the
+  # arguments passed to Go builders.
+  makeOverridable = f: orig: (f orig) // {
+    overrideGo = new: makeOverridable f (orig // (new orig));
+  };
+
+  # High-level build functions
+
+  # Build a Go program out of the specified files and dependencies.
+  program = { name, srcs, deps ? [], x_defs ? {} }:
+  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
+    export GOROOT_FINAL=go
+    ${go}/bin/go tool link -o $out/bin/${name} -buildid nix ${xFlags x_defs} ${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, sfiles ? [] }:
+  let
+    uniqueDeps = allDeps deps;
+
+    # The build steps below need to be executed conditionally for Go
+    # assembly if the analyser detected any *.s files.
+    #
+    # This is required for several popular packages (e.g. x/sys).
+    ifAsm = do: lib.optionalString (sfiles != []) do;
+    asmBuild = ifAsm ''
+      ${go}/bin/go tool asm -trimpath $PWD -I $PWD -I ${go}/share/go/pkg/include -D GOOS_linux -D GOARCH_amd64 -gensymabis -o ./symabis ${spaceOut sfiles}
+      ${go}/bin/go tool asm -trimpath $PWD -I $PWD -I ${go}/share/go/pkg/include -D GOOS_linux -D GOARCH_amd64 -o ./asm.o ${spaceOut sfiles}
+    '';
+    asmLink = ifAsm "-symabis ./symabis -asmhdr $out/go_asm.h";
+    asmPack = ifAsm ''
+      ${go}/bin/go tool pack r $out/${path}.a ./asm.o
+    '';
+  in (runCommand "golib-${name}" {} ''
+    mkdir -p $out/${path}
+    ${srcList path (map (s: "${s}") srcs)}
+    ${asmBuild}
+    ${go}/bin/go tool compile -pack ${asmLink} -o $out/${path}.a -trimpath=$PWD -trimpath=${go} -p ${path} ${includeSources uniqueDeps} ${spaceOut srcs}
+    ${asmPack}
+  '') // { goDeps = uniqueDeps; goImportPath = path; };
+
+  # Build a tree of Go libraries out of an external Go source
+  # directory that follows the standard Go layout and was not built
+  # with buildGo.nix.
+  #
+  # The derivation for each actual package will reside in an attribute
+  # named "gopkg", and an attribute named "gobin" for binaries.
+  external = import ./external { inherit pkgs program package; };
+
+  # Import support libraries needed for protobuf & gRPC support
+  protoLibs = import ./proto.nix {
+    inherit external;
+  };
+
+  # Build a Go library out of the specified protobuf definition.
+  proto = { name, proto, path ? name, extraDeps ? [] }: (makeOverridable package) {
+    inherit name path;
+    deps = [ protoLibs.goProto.proto.gopkg ] ++ extraDeps;
+    srcs = lib.singleton (runCommand "goproto-${name}.pb.go" {} ''
+      cp ${proto} ${baseNameOf proto}
+      ${protobuf}/bin/protoc --plugin=${protoLibs.goProto.protoc-gen-go.gopkg}/bin/protoc-gen-go \
+        --go_out=plugins=grpc,import_path=${baseNameOf path}:. ${baseNameOf proto}
+      mv *.pb.go $out
+    '');
+  };
+
+  # Build a Go library out of the specified gRPC definition.
+  grpc = args: proto (args // { extraDeps = [ protoLibs.goGrpc.gopkg ]; });
+
+in {
+  # Only the high-level builder functions are exposed, but made
+  # overrideable.
+  program = makeOverridable program;
+  package = makeOverridable package;
+  proto = makeOverridable proto;
+  grpc = makeOverridable grpc;
+  external = makeOverridable external;
+}