Add package generation for non development packages

This makes it possible to generate packages that you do not have a
local checkout for, e.g. running:
`gomod2nix generate --outdir example/ golang.org/x/tools/cmd/stringer`

This will be useful for packaging dependencies that you are not
developing, but just simply packaging.

.gitignore

@@ -1,3 +1,4 @@
 /gomod2nix
 result*
 /tests/*/gomod2nix.toml
+/tests/*/go.mod

builder/default.nix

@@ -151,8 +151,8 @@ let
     };
 
   buildGoApplication =
-    { modules
+    { modules ? pwd + "/gomod2nix.toml"
-    , src
+    , src ? pwd
     , pwd ? null
     , nativeBuildInputs ? [ ]
     , allowGoReference ? false
@@ -190,11 +190,19 @@ let
         inherit go modulesStruct localReplaceCommands;
       };
 
-      package = stdenv.mkDerivation (attrs // {
+      defaultPackage = modulesStruct.goPackagePath or "";
+
+      package = stdenv.mkDerivation (lib.optionalAttrs (defaultPackage != "")
+        {
+          pname = attrs.pname or baseNameOf defaultPackage;
+          version = lib.removePrefix "v" (modulesStruct.mod.${defaultPackage}).version;
+        } // attrs // {
         nativeBuildInputs = [ removeReferencesTo go ] ++ nativeBuildInputs;
 
         inherit (go) GOOS GOARCH;
 
+        inherit src;
+
         GO_NO_VENDOR_CHECKS = "1";
 
         GO111MODULE = "on";
@@ -302,6 +310,12 @@ let
           dir="$GOPATH/bin"
           [ -e "$dir" ] && cp -r $dir $out
 
+          ${lib.optionalString (lib.hasAttr "install" modulesStruct) ''
+            ${lib.concatStringsSep "\n" (map (x: "go install ${x}") (modulesStruct.install or [ ]))}
+            mkdir -p $out/bin
+            cp -a $GOPATH/bin/* $out/bin/
+          ''}
+
           runHook postInstall
         '';
 

cmd/root.go

@@ -2,6 +2,7 @@ package cmd
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"path/filepath"
 
@@ -11,39 +12,148 @@ import (
 	schema "github.com/tweag/gomod2nix/schema"
 )
 
+const directoryDefault = "./"
+
 var (
 	flagDirectory string
 	flagOutDir    string
-	flagMaxJobs   int
+	maxJobs       int
 )
 
+func generateFunc(cmd *cobra.Command, args []string) {
+	directory := flagDirectory
+	outDir := flagOutDir
+
+	// If we are dealing with a project packaged by passing packages on the command line
+	// we need to create a temporary project.
+	var tmpProj *generate.TempProject
+	if len(args) > 0 {
+		var err error
+
+		if directory != directoryDefault {
+			panic(fmt.Errorf("directory flag not supported together with import arguments"))
+		}
+		if outDir == "" {
+			pwd, err := os.Getwd()
+			if err != nil {
+				panic(err)
+			}
+
+			outDir = pwd
+		}
+
+		tmpProj, err = generate.NewTempProject(args)
+		if err != nil {
+			panic(err)
+		}
+		defer func() {
+			err := tmpProj.Remove()
+			if err != nil {
+				panic(err)
+			}
+		}()
+
+		directory = tmpProj.Dir
+	} else if outDir == "" {
+		// Default out to current working directory if we are developing some software in the current repo.
+		outDir = directory
+	}
+
+	// Write gomod2nix.toml
+	{
+		goMod2NixPath := filepath.Join(outDir, "gomod2nix.toml")
+		outFile := goMod2NixPath
+		pkgs, err := generate.GeneratePkgs(directory, goMod2NixPath, maxJobs)
+		if err != nil {
+			panic(fmt.Errorf("error generating pkgs: %v", err))
+		}
+
+		var goPackagePath string
+		var install []string
+
+		if tmpProj != nil {
+			install = tmpProj.Install
+			goPackagePath = tmpProj.GoPackagePath
+		}
+
+		output, err := schema.Marshal(pkgs, goPackagePath, install)
+		if err != nil {
+			panic(fmt.Errorf("error marshaling output: %v", err))
+		}
+
+		err = os.WriteFile(outFile, output, 0644)
+		if err != nil {
+			panic(fmt.Errorf("error writing file: %v", err))
+		}
+		log.Info(fmt.Sprintf("Wrote: %s", outFile))
+	}
+
+	// If we are dealing with a project packaged by passing packages on the command line, copy go.mod
+	if tmpProj != nil {
+		outMod := filepath.Join(outDir, "go.mod")
+
+		fin, err := os.Open(filepath.Join(tmpProj.Dir, "go.mod"))
+		if err != nil {
+			panic(fmt.Errorf("error opening go.mod: %v", err))
+		}
+
+		fout, err := os.Create(outMod)
+		if err != nil {
+			panic(fmt.Errorf("error creating go.mod: %v", err))
+		}
+
+		_, err = io.Copy(fout, fin)
+		if err != nil {
+			panic(fmt.Errorf("error writing go.mod: %v", err))
+		}
+
+		log.Info(fmt.Sprintf("Wrote: %s", outMod))
+	}
+}
+
 var rootCmd = &cobra.Command{
 	Use:   "gomod2nix",
 	Short: "Convert applications using Go modules -> Nix",
-	Run: func(cmd *cobra.Command, args []string) {
+	Run:   generateFunc,
-		err := generateInternal(flagDirectory, flagOutDir, flagMaxJobs)
-		if err != nil {
-			panic(err)
-		}
-	},
 }
 
 var generateCmd = &cobra.Command{
 	Use:   "generate",
 	Short: "Run gomod2nix.toml generator",
-	Run: func(cmd *cobra.Command, args []string) {
+	Run:   generateFunc,
-		err := generateInternal(flagDirectory, flagOutDir, flagMaxJobs)
+
-		if err != nil {
+	// func(cmd *cobra.Command, args []string) error {
-			panic(err)
+	// 	outDir := flagOutDir
-		}
+	// 	dir := flagDirectory
-	},
+
+	// 	if len(args) > 0 {
+	// 		tmpProj, err := generate.NewTempProject(args)
+	// 		if err != nil {
+	// 			panic(err)
+	// 		}
+	// 		defer tmpProj.Remove()
+
+	// 		dir = tmpProj.Dir
+	// 		outDir = "./tmp"
+	// 	}
+
+	// 	// dir := "/home/adisbladis/go/pkg/mod/github.com/kyleconroy/sqlc@v1.14.0"
+	// 	// fmt.Println(args)
+
+	// 	err := generateInternal(dir, outDir, flagMaxJobs)
+	// 	if err != nil {
+	// 		panic(err)
+	// 	}
+
+	// 	return nil
+	// },
 }
 
 var importCmd = &cobra.Command{
 	Use:   "import",
 	Short: "Import Go sources into the Nix store",
 	Run: func(cmd *cobra.Command, args []string) {
-		err := generate.ImportPkgs(flagDirectory, flagMaxJobs)
+		err := generate.ImportPkgs(flagDirectory, maxJobs)
 		if err != nil {
 			panic(err)
 		}
@@ -51,9 +161,9 @@ var importCmd = &cobra.Command{
 }
 
 func init() {
-	rootCmd.PersistentFlags().StringVar(&flagDirectory, "dir", "", "Go project directory")
+	rootCmd.PersistentFlags().StringVar(&flagDirectory, "dir", "./", "Go project directory")
 	rootCmd.PersistentFlags().StringVar(&flagOutDir, "outdir", "", "Output directory (defaults to project directory)")
-	rootCmd.PersistentFlags().IntVar(&flagMaxJobs, "jobs", 10, "Max number of concurrent jobs")
+	rootCmd.PersistentFlags().IntVar(&maxJobs, "jobs", 10, "Max number of concurrent jobs")
 
 	rootCmd.AddCommand(generateCmd)
 	rootCmd.AddCommand(importCmd)
@@ -65,29 +175,3 @@ func Execute() {
 		os.Exit(1)
 	}
 }
-
-func generateInternal(directory string, outDir string, maxJobs int) error {
-	if outDir == "" {
-		outDir = directory
-	}
-
-	goMod2NixPath := filepath.Join(outDir, "gomod2nix.toml")
-	outFile := goMod2NixPath
-	pkgs, err := generate.GeneratePkgs(directory, goMod2NixPath, maxJobs)
-	if err != nil {
-		return fmt.Errorf("error generating pkgs: %v", err)
-	}
-
-	output, err := schema.Marshal(pkgs)
-	if err != nil {
-		return fmt.Errorf("error marshaling output: %v", err)
-	}
-
-	err = os.WriteFile(outFile, output, 0644)
-	if err != nil {
-		return fmt.Errorf("error writing file: %v", err)
-	}
-	log.Info(fmt.Sprintf("Wrote: %s", outFile))
-
-	return nil
-}

generate/generate.go

@@ -1,4 +1,4 @@
-package fetch
+package generate
 
 import (
 	"bytes"

generate/temp.go

@@ -0,0 +1,166 @@
+package generate
+
+import (
+	"fmt"
+	"go/ast"
+	"go/printer"
+	"go/token"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strconv"
+	"strings"
+
+	log "github.com/sirupsen/logrus"
+	"golang.org/x/tools/go/vcs"
+)
+
+type TempProject struct {
+	Dir           string
+	Install       []string
+	GoPackagePath string
+}
+
+func NewTempProject(packages []string) (*TempProject, error) {
+	// Imports without version suffix
+	install := make([]string, len(packages))
+	for i, imp := range packages {
+		idx := strings.Index(imp, "@")
+		if idx == -1 {
+			idx = len(imp)
+		}
+
+		install[i] = imp[:idx]
+	}
+
+	var goPackagePath string
+
+	{
+		path := install[0]
+
+		log.WithFields(log.Fields{
+			"path": path,
+		}).Info("Finding repo root for import path")
+
+		repoRoot, err := vcs.RepoRootForImportPath(path, false)
+		if err != nil {
+			return nil, err
+		}
+
+		goPackagePath = repoRoot.Root
+	}
+
+	log.Info("Setting up temporary project")
+
+	dir, err := os.MkdirTemp("", "gomod2nix-proj")
+	if err != nil {
+		return nil, err
+	}
+
+	log.WithFields(log.Fields{
+		"dir": dir,
+	}).Info("Created temporary directory")
+
+	// Create tools.go
+	{
+		log.WithFields(log.Fields{
+			"dir": dir,
+		}).Info("Creating tools.go")
+
+		astFile := &ast.File{
+			Name: ast.NewIdent("main"),
+			Decls: []ast.Decl{
+				&ast.GenDecl{
+					Tok: token.IMPORT,
+					Specs: func() []ast.Spec {
+						specs := make([]ast.Spec, len(install))
+
+						i := 0
+						for _, imp := range install {
+							specs[i] = &ast.ImportSpec{
+								Name: ast.NewIdent("_"),
+								Path: &ast.BasicLit{
+									ValuePos: token.NoPos,
+									Kind:     token.STRING,
+									Value:    strconv.Quote(imp),
+								},
+							}
+
+							i++
+						}
+
+						return specs
+					}(),
+				},
+			},
+		}
+
+		f, err := os.Create(filepath.Join(dir, "tools.go"))
+		if err != nil {
+			return nil, fmt.Errorf("Error creating tools.go: %v", err)
+		}
+		defer f.Close()
+
+		fset := token.NewFileSet()
+		err = printer.Fprint(f, fset, astFile)
+		if err != nil {
+			return nil, fmt.Errorf("error writing tools.go: %v", err)
+		}
+
+		log.WithFields(log.Fields{
+			"dir": dir,
+		}).Info("Created tools.go")
+	}
+
+	// Set up go module
+	{
+		log.WithFields(log.Fields{
+			"dir": dir,
+		}).Info("Initializing go.mod")
+
+		cmd := exec.Command("go", "mod", "init", "gomod2nix/dummy/package")
+		cmd.Dir = dir
+		cmd.Stderr = os.Stderr
+
+		_, err := cmd.Output()
+		if err != nil {
+			return nil, fmt.Errorf("error creating go module: %v", err)
+		}
+
+		log.WithFields(log.Fields{
+			"dir": dir,
+		}).Info("Done initializing go.mod")
+
+		// For every dependency fetch it
+		for _, imp := range packages {
+			log.WithFields(log.Fields{
+				"dir": dir,
+				"dep": imp,
+			}).Info("Getting dependency")
+
+			cmd := exec.Command("go", "get", "-d", imp)
+			cmd.Dir = dir
+			cmd.Stderr = os.Stderr
+
+			_, err := cmd.Output()
+			if err != nil {
+				return nil, fmt.Errorf("error fetching '%s': %v", imp, err)
+			}
+
+			log.WithFields(log.Fields{
+				"dir": dir,
+				"dep": imp,
+			}).Info("Done getting dependency")
+		}
+	}
+
+	return &TempProject{
+		Dir:           dir,
+		Install:       install,
+		GoPackagePath: goPackagePath,
+	}, nil
+}
+
+func (t *TempProject) Remove() error {
+	return os.RemoveAll(t.Dir)
+}

go.mod

@@ -6,12 +6,13 @@ require (
 	github.com/BurntSushi/toml v1.1.0
 	github.com/nix-community/go-nix v0.0.0-20220612195009-5f5614f7ca47
 	github.com/sirupsen/logrus v1.8.1
+	github.com/spf13/cobra v1.4.0
 	golang.org/x/mod v0.5.1
+	golang.org/x/tools v0.0.0-20210106214847-113979e3529a
 )
 
 require (
 	github.com/inconshreveable/mousetrap v1.0.0 // indirect
-	github.com/spf13/cobra v1.4.0 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
 	golang.org/x/sys v0.0.0-20220610221304-9f5ed59c137d // indirect
 	golang.org/x/xerrors v0.0.0-20220609144429-65e65417b02f // indirect

go.sum

@@ -15,6 +15,7 @@ github.com/coreos/go-semver v0.2.0/go.mod h1:nnelYz7RCh+5ahJtPPxZlU+153eP4D4r3Ee
 github.com/cpuguy83/go-md2man v1.0.10/go.mod h1:SmD6nW6nTyfqj6ABTjUi3V3JVMnlJmwcJI5acqYI6dE=
 github.com/cpuguy83/go-md2man/v2 v2.0.1/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dgraph-io/badger/v3 v3.2103.2/go.mod h1:RHo4/GmYcKKh5Lxu63wLEMHJ70Pac2JqZRYGhlyAo2M=
 github.com/dgraph-io/ristretto v0.1.0/go.mod h1:fux0lOrBhrVCJd3lcTHsIJhq1T2rokOu6v9Vcb3Q9ug=
@@ -48,6 +49,7 @@ github.com/nix-community/go-nix v0.0.0-20220612195009-5f5614f7ca47 h1:K270nNzKXB
 github.com/nix-community/go-nix v0.0.0-20220612195009-5f5614f7ca47/go.mod h1:eE1NFc/GHPnxAhTTuxIfB6JSvRQdMVQCMQqRrGRWWfQ=
 github.com/pelletier/go-toml v1.2.0/go.mod h1:5z9KED0ma1S8pY6P1sdut58dfprrGBbd/94hg7ilaic=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/russross/blackfriday v1.5.2/go.mod h1:JO/DiYxRf+HjHt06OyowR9PTA263kcR/rfWxYHBV53g=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
@@ -68,6 +70,7 @@ github.com/spf13/viper v1.3.2/go.mod h1:ZiWeW+zYFKm7srdB9IoDzzZXaJaI5eL9QjNiN/DM
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
+github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/ugorji/go/codec v0.0.0-20181204163529-d75b2dcb6bc8/go.mod h1:VFNgLljTbGfSG7qAOspJ7OScBnGdDN/yBr0sguwnwf0=
 github.com/xordataexchange/crypt v0.0.3-0.20170626215501-b2862e3d0a77/go.mod h1:aYKd//L2LvnjZzWKhF00oedf4jCCReLcmhLdhm1A27Q=
@@ -119,6 +122,7 @@ golang.org/x/tools v0.0.0-20190226205152-f727befe758c/go.mod h1:9Yl7xja0Znq3iFh3
 golang.org/x/tools v0.0.0-20190311212946-11955173bddd/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
 golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.0.0-20200619180055-7c47624df98f/go.mod h1:EkVYQZoAsY45+roYkvgYkIh4xh/qjgUK9TdY2XT94GE=
+golang.org/x/tools v0.0.0-20210106214847-113979e3529a h1:CB3a9Nez8M13wwlr/E2YtwoU+qYHKfC+JrDa45RXXoQ=
 golang.org/x/tools v0.0.0-20210106214847-113979e3529a/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
@@ -137,5 +141,6 @@ gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo=
 gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=

gomod2nix.toml

@@ -1,4 +1,4 @@
-schema = 1
+schema = 2
 
 [mod]
   [mod."cloud.google.com/go"]

schema/schema.go

@@ -6,7 +6,7 @@ import (
 	"os"
 )
 
-const SchemaVersion = 1
+const SchemaVersion = 2
 
 type Package struct {
 	GoPackagePath string `toml:"-"`
@@ -18,12 +18,20 @@ type Package struct {
 type Output struct {
 	SchemaVersion int                 `toml:"schema"`
 	Mod           map[string]*Package `toml:"mod"`
+
+	// Packages with passed import paths trigger `go install` based on this list
+	Install []string `toml:"install,omitempty"`
+
+	// Packages with passed import paths has a "default package" which pname & version is inherit from
+	GoPackagePath string `toml:"goPackagePath,omitempty"`
 }
 
-func Marshal(pkgs []*Package) ([]byte, error) {
+func Marshal(pkgs []*Package, goPackagePath string, install []string) ([]byte, error) {
 	out := &Output{
 		SchemaVersion: SchemaVersion,
 		Mod:           make(map[string]*Package),
+		Install:       install,
+		GoPackagePath: goPackagePath,
 	}
 
 	for _, pkg := range pkgs {

tests/cli-args/default.nix

@@ -0,0 +1,17 @@
+{ runCommand, buildGoApplication }:
+
+let
+  drv = buildGoApplication {
+    pname = "stringer";
+    pwd = ./.;
+  };
+in
+assert drv.version == "0.1.11";
+runCommand "cli-args-stringer-assert" { } ''
+  if ! test -f ${drv}/bin/stringer; then
+    echo "stringer command not found in env!"
+    exit 1
+  fi
+
+  ln -s ${drv} $out
+''

tests/cli-args/script

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+set -euo pipefail
+cd "${0%/*}"
+exec $GOMOD2NIX generate  "golang.org/x/tools/cmd/stringer@v0.1.11"

tests/run.go

@@ -13,11 +13,15 @@ import (
 	"sync"
 )
 
-func runProcess(prefix string, command string, args ...string) error {
+func runProcess(prefix string, env []string, command string, args ...string) error {
 	fmt.Printf("%s: Executing %s %s\n", prefix, command, args)
 
 	cmd := exec.Command(command, args...)
 
+	if env != nil {
+		cmd.Env = env
+	}
+
 	stdoutReader, err := cmd.StdoutPipe()
 	if err != nil {
 		return err
@@ -61,18 +65,27 @@ func contains(haystack []string, needle string) bool {
 
 func runTest(rootDir string, testDir string) error {
 	prefix := testDir
-	cmdPath := filepath.Join(rootDir, "..", "gomod2nix")
 	testDir = filepath.Join(rootDir, testDir)
+	cmdPath := filepath.Join(rootDir, "..", "gomod2nix")
 
-	if _, err := os.Stat(filepath.Join(testDir, "go.mod")); err == nil {
+	if _, err := os.Stat(filepath.Join(testDir, "script")); err == nil {
-		err := runProcess(prefix, cmdPath, "--dir", testDir, "--outdir", testDir)
+		env := append(os.Environ(), "GOMOD2NIX="+cmdPath)
+		err := runProcess(prefix, env, filepath.Join(testDir, "script"))
 		if err != nil {
 			return err
 		}
+
+	} else {
+		if _, err := os.Stat(filepath.Join(testDir, "go.mod")); err == nil {
+			err := runProcess(prefix, nil, cmdPath, "--dir", testDir, "--outdir", testDir)
+			if err != nil {
+				return err
+			}
+		}
 	}
 
 	buildExpr := fmt.Sprintf("with (import <nixpkgs> { overlays = [ (import %s/../overlay.nix) ]; }); callPackage %s {}", rootDir, testDir)
-	err := runProcess(prefix, "nix-build", "--no-out-link", "--expr", buildExpr)
+	err := runProcess(prefix, nil, "nix-build", "--no-out-link", "--expr", buildExpr)
 	if err != nil {
 		return err
 	}