Prevent side effects when looking for config files. (#1328)

As noted in #1156 (comment), `xdg.ConfigFile` has side effects. One of the consequences of the side effects is that sometimes, when simply wanting to check for existence, we would error out entirely because the path wasn't writable.

This splits the process of creating and reading a config file path, which means that the error won't be encountered unless a user is explicitly trying to create a configuration file. (Which *should* be an error.)

Fixes #1270

cli/internal/config/config_file.go

@@ -63,7 +63,21 @@ func WriteRepoConfigFile(fsys afero.Fs, repoRoot fs.AbsolutePath, toWrite *Turbo
 	return writeConfigFile(fsys, path, toWrite)
 }
 
-func userConfigPath(fsys afero.Fs) (fs.AbsolutePath, error) {
+func getUserConfigPath(fsys afero.Fs) (fs.AbsolutePath, error) {
+	path, err := xdg.SearchConfigFile(filepath.Join("turborepo", "config.json"))
+	// Not finding an existing config file is not an error.
+	// We simply bail with no path, and no error.
+	if err != nil {
+		return "", nil
+	}
+	absPath, err := fs.CheckedToAbsolutePath(path)
+	if err != nil {
+		return "", err
+	}
+	return absPath, nil
+}
+
+func createUserConfigPath(fsys afero.Fs) (fs.AbsolutePath, error) {
 	path, err := xdg.ConfigFile(filepath.Join("turborepo", "config.json"))
 	if err != nil {
 		return "", err
@@ -79,7 +93,7 @@ func userConfigPath(fsys afero.Fs) (fs.AbsolutePath, error) {
 // configuration file. This is for values that are not shared with a team, such
 // as credentials.
 func WriteUserConfigFile(fsys afero.Fs, config *TurborepoConfig) error {
-	path, err := userConfigPath(fsys)
+	path, err := createUserConfigPath(fsys)
 	if err != nil {
 		return err
 	}
@@ -108,10 +122,19 @@ func readConfigFile(fsys afero.Fs, path fs.AbsolutePath, defaults func() *Turbor
 
 // ReadUserConfigFile reads a user config file
 func ReadUserConfigFile(fsys afero.Fs) (*TurborepoConfig, error) {
-	path, err := userConfigPath(fsys)
+	path, err := getUserConfigPath(fsys)
+
+	// Check the error first, that means we got a hit, but failed on path conversion.
 	if err != nil {
 		return nil, err
 	}
+
+	// Otherwise, we just didn't find anything, which isn't an error.
+	if path == "" {
+		return nil, nil
+	}
+
+	// Found something!
 	return readConfigFile(fsys, path, defaultUserConfig)
 }
 
@@ -123,9 +146,18 @@ func ReadRepoConfigFile(fsys afero.Fs, repoRoot fs.AbsolutePath) (*TurborepoConf
 
 // DeleteUserConfigFile deletes a user config file
 func DeleteUserConfigFile(fsys afero.Fs) error {
-	path, err := userConfigPath(fsys)
+	path, err := getUserConfigPath(fsys)
+
+	// Check the error first, that means we got a hit, but failed on path conversion.
 	if err != nil {
 		return err
 	}
+
+	// Otherwise, we just didn't find anything, which isn't an error.
+	if path == "" {
+		return nil
+	}
+
+	// Found a config file!
 	return fs.RemoveFile(fsys, path)
 }

cli/internal/config/config_file_test.go

@@ -9,6 +9,46 @@ import (
 	"github.com/vercel/turborepo/cli/internal/fs"
 )
 
+func Test_UserConfigPath(t *testing.T) {
+	fsys := afero.NewMemMapFs()
+
+	t.Run("get doesn't create a path", func(t *testing.T) {
+		// XDG is not filesystem aware. Clean up first.
+		path, _ := createUserConfigPath(fsys)
+		err := os.Remove(path.Dir().ToString())
+		if err != nil {
+			t.Errorf("failed to clean up first: %v", err)
+		}
+
+		getConfigPath, getConfigPathErr := getUserConfigPath(fsys)
+		if getConfigPathErr != nil {
+			t.Errorf("failed to run getUserConfigPath: %v", getConfigPathErr)
+		}
+
+		// The main thing we want to do is make sure that we don't have side effects.
+		// We know where it would attempt to create a directory already.
+		if getConfigPath == "" {
+			getConfigPath = path
+		}
+
+		getConfigDir := getConfigPath.Dir()
+		getCheck, _ := os.Stat(getConfigDir.ToString())
+		if getCheck != nil {
+			t.Error("getUserConfigPath() had side effects.")
+		}
+
+		createConfigPath, createErr := createUserConfigPath(fsys)
+		if createErr != nil {
+			t.Errorf("createUserConfigPath() errored: %v.", createErr)
+		}
+		createConfigDir := createConfigPath.Dir()
+		createCheck, _ := os.Stat(createConfigDir.ToString())
+		if createCheck == nil {
+			t.Error("createUserConfigPath() did not create the path.")
+		}
+	})
+}
+
 func TestReadRepoConfigWhenMissing(t *testing.T) {
 	fsys := afero.NewMemMapFs()
 	cwd, err := fs.GetCwd()
@@ -102,7 +142,7 @@ func TestReadUserConfigWhenMissing(t *testing.T) {
 }
 
 func TestWriteUserConfig(t *testing.T) {
-	fsys := afero.NewMemMapFs()
+	fsys := afero.NewOsFs()
 	initial := defaultUserConfig()
 	initial.Token = "my-token"
 	initial.ApiUrl = "https://api.vercel.com" // should be overridden

cli/internal/login/login_test.go

@@ -105,7 +105,7 @@ func (tr *testResult) getTestLogin() login {
 }
 
 func newTest(t *testing.T, redirectedURL string) *testResult {
-	fsys := afero.NewMemMapFs()
+	fsys := afero.NewOsFs()
 	stepCh := make(chan struct{}, 1)
 	cwd, err := fs.GetCwd()
 	if err != nil {