more tests and do not error out if user not found

pkg/commands/user.go

@@ -17,6 +17,8 @@ limitations under the License.
 package commands
 
 import (
+	"fmt"
+	"github.com/pkg/errors"
 	"strings"
 
 	"github.com/GoogleContainerTools/kaniko/pkg/dockerfile"
@@ -43,17 +45,13 @@ func (r *UserCommand) ExecuteCommand(config *v1.Config, buildArgs *dockerfile.Bu
 	replacementEnvs := buildArgs.ReplacementEnvs(config.Env)
 	userStr, err := util.ResolveEnvironmentReplacement(userAndGroup[0], replacementEnvs, false)
 	if err != nil {
-		return err
+		return errors.Wrap(err, fmt.Sprintf("resolving user %s", userAndGroup[0]))
 	}
-	userObj, err := Lookup(userStr)
-	if err != nil {
-		return err
-	}
-	groupStr := userObj.Gid
+	var groupStr = setGroupDefault(userStr)
 	if len(userAndGroup) > 1 {
 		groupStr, err = util.ResolveEnvironmentReplacement(userAndGroup[1], replacementEnvs, false)
 		if err != nil {
-			return err
+			return errors.Wrap(err, fmt.Sprintf("resolving group %s", userAndGroup[1]))
 		}
 	}
 
@@ -66,3 +64,12 @@ func (r *UserCommand) ExecuteCommand(config *v1.Config, buildArgs *dockerfile.Bu
 func (r *UserCommand) String() string {
 	return r.cmd.String()
 }
+
+func setGroupDefault(userStr string) string {
+	userObj, err := Lookup(userStr)
+	if err != nil {
+		logrus.Debugf("could not lookup user %s. Setting group empty", userStr)
+		return ""
+	}
+	return userObj.Gid
+}

pkg/commands/user_test.go

@@ -16,6 +16,7 @@ limitations under the License.
 package commands
 
 import (
+	"fmt"
 	"os/user"
 	"testing"
 
@@ -29,66 +30,70 @@ import (
 
 var userTests = []struct {
 	user        string
-	userObj     user.User
+	userObj     *user.User
 	expectedUID string
 	expectedGID string
 }{
 	{
 		user:        "root",
-		userObj:     user.User{Uid: "root", Gid: "root"},
+		userObj:     &user.User{Uid: "root", Gid: "root"},
 		expectedUID: "root:root",
 	},
 	{
 		user:        "root-add",
-		userObj:     user.User{Uid: "root-add", Gid: "root"},
+		userObj:     &user.User{Uid: "root-add", Gid: "root"},
 		expectedUID: "root-add:root",
 	},
 	{
 		user:        "0",
-		userObj:     user.User{Uid: "0", Gid: "0"},
+		userObj:     &user.User{Uid: "0", Gid: "0"},
 		expectedUID: "0:0",
 	},
 	{
 		user:        "fakeUser",
-		userObj:     user.User{Uid: "fakeUser", Gid: "fakeUser"},
+		userObj:     &user.User{Uid: "fakeUser", Gid: "fakeUser"},
 		expectedUID: "fakeUser:fakeUser",
 	},
 	{
 		user:        "root:root",
-		userObj:     user.User{Uid: "root", Gid: "some"},
+		userObj:     &user.User{Uid: "root", Gid: "some"},
 		expectedUID: "root:root",
 	},
 	{
 		user:        "0:root",
-		userObj:     user.User{Uid: "0"},
+		userObj:     &user.User{Uid: "0"},
 		expectedUID: "0:root",
 	},
 	{
 		user:        "root:0",
-		userObj:     user.User{Uid: "root"},
+		userObj:     &user.User{Uid: "root"},
 		expectedUID: "root:0",
 		expectedGID: "f0",
 	},
 	{
 		user:        "0:0",
-		userObj:     user.User{Uid: "0"},
+		userObj:     &user.User{Uid: "0"},
 		expectedUID: "0:0",
 	},
 	{
 		user:        "$envuser",
-		userObj:     user.User{Uid: "root", Gid: "root"},
+		userObj:     &user.User{Uid: "root", Gid: "root"},
 		expectedUID: "root:root",
 	},
 	{
 		user:        "root:$envgroup",
-		userObj:     user.User{Uid: "root"},
+		userObj:     &user.User{Uid: "root"},
 		expectedUID: "root:grp",
 	},
 	{
 		user:        "some:grp",
-		userObj:     user.User{Uid: "some"},
+		userObj:     &user.User{Uid: "some"},
 		expectedUID: "some:grp",
 	},
+	{
+		user:        "some",
+		expectedUID: "some:",
+	},
 }
 
 func TestUpdateUser(t *testing.T) {
@@ -105,7 +110,10 @@ func TestUpdateUser(t *testing.T) {
 			},
 		}
 		Lookup = func(_ string) (*user.User, error) {
-			return &test.userObj, nil
+			if test.userObj != nil {
+				return test.userObj, nil
+			}
+			return nil, fmt.Errorf("error while looking up user.")
 		}
 		defer func() { Lookup = util.Lookup }()
 		buildArgs := dockerfile.NewBuildArgs([]string{})