Replace "XDG_RUNTIME_DIR" literals with a constant

pkg/shell/paths_unix.go

@@ -7,6 +7,8 @@ import (
 	"os"
 	"path/filepath"
 	"syscall"
+
+	"github.com/elves/elvish/pkg/util"
 )
 
 // Returns a "run directory" for storing ephemeral files, which is guaranteed
@@ -38,8 +40,8 @@ func getSecureRunDir() (string, error) {
 // preference.
 func getRunDirCandidates() []string {
 	tmpDirPath := filepath.Join(os.TempDir(), fmt.Sprintf("elvish-%d", os.Getuid()))
-	if os.Getenv("XDG_RUNTIME_DIR") != "" {
-		xdgDirPath := filepath.Join(os.Getenv("XDG_RUNTIME_DIR"), "elvish")
+	if os.Getenv(util.EnvXDG_RUNTIME_DIR) != "" {
+		xdgDirPath := filepath.Join(os.Getenv(util.EnvXDG_RUNTIME_DIR), "elvish")
 		return []string{xdgDirPath, tmpDirPath}
 	}
 	return []string{tmpDirPath}

pkg/shell/paths_unix_test.go

@@ -45,7 +45,7 @@ func TestGetSecureRunDir_PrefersTmpWhenOnlyItExists(t *testing.T) {
 func TestGetSecureRunDir_PrefersTmpWhenXdgEnvIsEmpty(t *testing.T) {
 	_, tmp, cleanup := setupForSecureRunDir()
 	defer cleanup()
-	os.Setenv("XDG_RUNTIME_DIR", "")
+	os.Setenv(util.EnvXDG_RUNTIME_DIR, "")
 	testSecureRunDir(t, filepath.Join(tmp, elvishDashUid), false)
 }
 
@@ -60,8 +60,8 @@ func setupForSecureRunDir() (xdgRuntimeDir, tmpDir string, cleanup func()) {
 	xdgRuntimeDir, xdgCleanup := util.TestDir()
 	tmpDir, tmpCleanup := util.TestDir()
 	envCleanup := withTempEnvs(map[string]string{
-		"XDG_RUNTIME_DIR": xdgRuntimeDir,
-		"TMPDIR":          tmpDir,
+		util.EnvXDG_RUNTIME_DIR: xdgRuntimeDir,
+		"TMPDIR":                tmpDir,
 	})
 	return xdgRuntimeDir, tmpDir, func() {
 		envCleanup()

pkg/util/util.go

@@ -6,10 +6,11 @@ package util
 // Note that some of these env vars may be significant only in special
 // circumstances; such as when running unit tests.
 const (
-	EnvHOME      = "HOME"
-	EnvPATH      = "PATH"
-	EnvPATHEXT   = "PATHEXT"
-	EnvPWD       = "PWD"
-	EnvSHLVL     = "SHLVL"
-	EnvLS_COLORS = "LS_COLORS"
+	EnvHOME            = "HOME"
+	EnvPATH            = "PATH"
+	EnvPATHEXT         = "PATHEXT"
+	EnvPWD             = "PWD"
+	EnvSHLVL           = "SHLVL"
+	EnvLS_COLORS       = "LS_COLORS"
+	EnvXDG_RUNTIME_DIR = "XDG_RUNTIME_DIR"
 )