Update xdg.RuntimeFile logic

README.md

@@ -79,7 +79,7 @@ Sensible fallback locations are used for the folders which are not set.
 | <kbd><b>XDG_CONFIG_DIRS</b></kbd>                              | <kbd>/etc/xdg</kbd>                                                       | <kbd>~/Library/Preferences</kbd><br/><kbd>/Library/Application&nbsp;Support</kbd><br/><kbd>/Library/Preferences</kbd><br/><kbd>&#126;/.config</kbd> | <kbd>/lib</kbd>                                                             |
 | <kbd><b>XDG_STATE_HOME</b></kbd>                               | <kbd>~/.local/state</kbd>                                                 | <kbd>~/Library/Application&nbsp;Support</kbd>                                                                                                       | <kbd>$home/lib/state</kbd>                                                  |
 | <kbd><b>XDG_CACHE_HOME</b></kbd>                               | <kbd>~/.cache</kbd>                                                       | <kbd>~/Library/Caches</kbd>                                                                                                                         | <kbd>$home/lib/cache</kbd>                                                  |
-| <kbd><b>XDG_RUNTIME_DIR</b></kbd>                              | <kbd>/run/user/UID</kbd>                                                  | <kbd>~/Library/Application&nbsp;Support</kbd>                                                                                                       | <kbd>/tmp</kbd>                                                             |
+| <kbd><b>XDG_RUNTIME_DIR</b></kbd>                              | <kbd>/run/user/$UID</kbd>                                                 | <kbd>~/Library/Application&nbsp;Support</kbd>                                                                                                       | <kbd>/tmp</kbd>                                                             |
 | <kbd><b>XDG_BIN_HOME</b></kbd>                                 | <kbd>~/.local/bin</kbd>                                                   | <kbd>~/.local/bin</kbd>                                                                                                                             | <kbd>$home/bin</kbd>                                                        |
 
 </details>

base_dirs.go

@@ -1,6 +1,10 @@
 package xdg
 
-import "github.com/adrg/xdg/internal/pathutil"
+import (
+	"os"
+
+	"github.com/adrg/xdg/internal/pathutil"
+)
 
 // XDG Base Directory environment variables.
 const (
@@ -48,7 +52,13 @@ func (bd baseDirectories) cacheFile(relPath string) (string, error) {
 }
 
 func (bd baseDirectories) runtimeFile(relPath string) (string, error) {
-	return pathutil.Create(relPath, []string{bd.runtime})
+	var paths []string
+	for _, p := range pathutil.Unique([]string{bd.runtime, os.TempDir()}) {
+		if pathutil.Exists(p) {
+			paths = append(paths, p)
+		}
+	}
+	return pathutil.Create(relPath, paths)
 }
 
 func (bd baseDirectories) searchDataFile(relPath string) (string, error) {

internal/pathutil/pathutil.go

@@ -4,7 +4,6 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
-	"strings"
 )
 
 // Unique eliminates the duplicate paths from the provided slice and returns
@@ -52,7 +51,6 @@ func First(paths []string) string {
 // relative to the selected parent path.
 func Create(name string, paths []string) (string, error) {
 	searchedPaths := make([]string, 0, len(paths))
-
 	for _, p := range paths {
 		p = filepath.Join(p, name)
 
@@ -67,16 +65,15 @@ func Create(name string, paths []string) (string, error) {
 		searchedPaths = append(searchedPaths, dir)
 	}
 
-	return "", fmt.Errorf("could not create any of the following paths: %s",
-		strings.Join(searchedPaths, ", "))
+	return "", fmt.Errorf("could not create any of the following paths: %v",
+		searchedPaths)
 }
 
 // Search searches for the file with the specified `name` in the provided
 // slice of `paths`. The `name` parameter must contain the name of the file,
 // but it can also contain a set of parent directories.
 func Search(name string, paths []string) (string, error) {
 	searchedPaths := make([]string, 0, len(paths))
-
 	for _, p := range paths {
 		p = filepath.Join(p, name)
 		if Exists(p) {
@@ -86,8 +83,8 @@ func Search(name string, paths []string) (string, error) {
 		searchedPaths = append(searchedPaths, filepath.Dir(p))
 	}
 
-	return "", fmt.Errorf("could not locate `%s` in any of the following paths: %s",
-		filepath.Base(name), strings.Join(searchedPaths, ", "))
+	return "", fmt.Errorf("could not locate `%s` in any of the following paths: %v",
+		filepath.Base(name), searchedPaths)
 }
 
 // EnvPath returns the value of the environment variable with the specified

xdg.go

@@ -161,8 +161,9 @@ func CacheFile(relPath string) (string, error) {
 // The relPath parameter must contain the name of the runtime file, and
 // optionally, a set of parent directories (e.g. appname/app.pid).
 // If the specified directories do not exist, they will be created relative
-// to the base runtime directory. On failure, an error containing the
-// attempted paths is returned.
+// to the base runtime directory. If the base runtime directory does not exist,
+// the operating system's temporary directory is used as a fallback. On failure,
+// an error containing the attempted paths is returned.
 func RuntimeFile(relPath string) (string, error) {
 	return baseDirs.runtimeFile(relPath)
 }

xdg_test.go

@@ -199,3 +199,20 @@ func TestInvalidPaths(t *testing.T) {
 		require.Error(t, err)
 	}
 }
+
+func TestNonExistentRuntimeDir(t *testing.T) {
+	var (
+		envRuntimeDirVar      = "XDG_RUNTIME_DIR"
+		originalRuntimeDir    = xdg.RuntimeDir
+		nonExistentRuntimeDir = filepath.Join(xdg.Home, "runtime")
+	)
+	defer os.Setenv(envRuntimeDirVar, originalRuntimeDir)
+
+	require.NoError(t, os.Setenv(envRuntimeDirVar, nonExistentRuntimeDir))
+	xdg.Reload()
+	require.Equal(t, nonExistentRuntimeDir, xdg.RuntimeDir)
+
+	p, err := xdg.RuntimeFile("app.pid")
+	require.NoError(t, err)
+	require.Equal(t, filepath.Clean(os.TempDir()), filepath.Dir(p))
+}