Update xdg.SearchRuntimeFile to also look in the temporary directory

README.md

@@ -207,6 +207,9 @@ func main() {
 	// ConfigFile takes one parameter which must contain the name of the file,
 	// but it can also contain a set of parent directories. If the directories
 	// don't exist, they will be created relative to the base config directory.
+	// It is recommended for files to be saved inside an application directory
+	// relative to the base directory rather than directly inside the base
+	// directory (e.g. `appname/config.yaml` instead of `appname-config.yaml`).
 	configFilePath, err := xdg.ConfigFile("appname/config.yaml")
 	if err != nil {
 		log.Fatal(err)

base_dirs.go

@@ -78,5 +78,5 @@ func (bd baseDirectories) searchCacheFile(relPath string) (string, error) {
 }
 
 func (bd baseDirectories) searchRuntimeFile(relPath string) (string, error) {
-	return pathutil.Search(relPath, []string{bd.runtime})
+	return pathutil.Search(relPath, pathutil.Unique([]string{bd.runtime, os.TempDir()}))
 }

doc.go

@@ -48,6 +48,9 @@ XDG Base Directory
 		// ConfigFile takes one parameter which must contain the name of the file,
 		// but it can also contain a set of parent directories. If the directories
 		// don't exist, they will be created relative to the base config directory.
+		// It is recommended for files to be saved inside an application directory
+		// relative to the base directory rather than directly inside the base
+		// directory (e.g. `appname/config.yaml` instead of `appname-config.yaml`).
 		configFilePath, err := xdg.ConfigFile("appname/config.yaml")
 		if err != nil {
 			log.Fatal(err)

xdg.go

@@ -202,8 +202,11 @@ func SearchCacheFile(relPath string) (string, error) {
 
 // SearchRuntimeFile searches for the specified file in the runtime search path.
 // 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
-// file cannot be found, an error specifying the searched path is returned.
+// optionally, a set of parent directories (e.g. appname/app.pid). The runtime
+// file is also searched in the operating system's temporary directory in order
+// to cover cases in which the runtime base directory does not exist or is not
+// accessible. If the file cannot be found, an error specifying the searched
+// paths is returned.
 func SearchRuntimeFile(relPath string) (string, error) {
 	return baseDirs.searchRuntimeFile(relPath)
 }

xdg_test.go

@@ -202,6 +202,7 @@ func TestInvalidPaths(t *testing.T) {
 
 func TestNonExistentRuntimeDir(t *testing.T) {
 	var (
+		runtimeFiles          = []string{"app.pid", "appname/app.pid"}
 		envRuntimeDirVar      = "XDG_RUNTIME_DIR"
 		originalRuntimeDir    = xdg.RuntimeDir
 		nonExistentRuntimeDir = filepath.Join(xdg.Home, "runtime")
@@ -212,7 +213,18 @@ func TestNonExistentRuntimeDir(t *testing.T) {
 	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))
+	for _, runtimeFile := range runtimeFiles {
+		suggestedPath, err := xdg.RuntimeFile(runtimeFile)
+		require.NoError(t, err)
+		require.Equal(t, true, strings.HasPrefix(suggestedPath, os.TempDir()))
+
+		f, err := os.Create(suggestedPath)
+		require.NoError(t, err)
+		require.NoError(t, f.Close())
+		defer os.Remove(suggestedPath)
+
+		foundPath, err := xdg.SearchRuntimeFile(runtimeFile)
+		require.NoError(t, err)
+		require.Equal(t, suggestedPath, foundPath)
+	}
 }