Return configuration save failures

config/user_config.go

@@ -46,20 +46,22 @@ type eUser struct {
 	LocallyMuted bool // Changed from Muted to LocallyMuted to match User struct
 }
 
-func (c *Config) SaveConfig() {
-	var data []byte
+// SaveConfig atomically replaces the persisted configuration. Errors are
+// returned so an unavailable directory cannot crash the client.
+func (c *Config) SaveConfig() error {
 	data, err := toml.Marshal(c.config)
 	if err != nil {
-		panic(err)
+		return err
 	}
-	err = ioutil.WriteFile(c.fn+".tmp", data, 0600)
-	if err != nil {
-		panic(err)
+	tmp := c.fn + ".tmp"
+	if err := ioutil.WriteFile(tmp, data, 0600); err != nil {
+		return err
 	}
-	err = os.Rename(c.fn+".tmp", c.fn)
-	if err != nil {
-		panic(err)
+	if err := os.Rename(tmp, c.fn); err != nil {
+		_ = os.Remove(tmp)
+		return err
 	}
+	return nil
 }
 
 func key(k uiterm.Key) *uiterm.Key {

config/user_config_save_test.go

@@ -0,0 +1,16 @@
+package config
+
+import (
+	"path/filepath"
+	"testing"
+)
+
+// Regression: a configuration write failure panicked the client instead of
+// returning an error to the caller.
+func TestSaveConfigReturnsWriteError(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "missing", "barnard.toml")
+	cfg := NewConfig(&path)
+	if err := cfg.SaveConfig(); err == nil {
+		t.Fatal("expected configuration write error")
+	}
+}