fix(setup): test override file existence before treating cat output as config (#215)

client.Run uses CombinedOutput, so when
`/mnt/nv/OverrideSdkPrivateCfg.xml` is absent (the default for devices
migrated with pre-0.71.0 code) the cat stderr is returned as the
override config and surfaced to the migration page UI as "Current Config
(on Speaker)". Gate the branch on `[ -f ... ]` first, mirroring the
legacy .original check.

Relates to #209
Relates to #214

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

pkg/service/setup/setup.go

@@ -508,14 +508,18 @@ func (m *Manager) checkCurrentConfig(summary *MigrationSummary, deviceIP string)
 	client := m.NewSSH(deviceIP)
 
 	// Check for override config (new-style XML migration) — the device prefers this over the original.
-	if overrideCfg, _ := client.Run(fmt.Sprintf("cat %s", SoundTouchSdkPrivateCfgOverridePath)); overrideCfg != "" {
-		summary.SSHSuccess = true
-		// The untouched factory config at the original path is the OriginalConfig.
-		if origCfg, _ := client.Run(fmt.Sprintf("cat %s", SoundTouchSdkPrivateCfgPath)); origCfg != "" {
-			summary.OriginalConfig = origCfg
-		}
+	// Test existence first: client.Run uses CombinedOutput, so a missing file's stderr would otherwise
+	// be returned as a non-empty config and surfaced to the UI.
+	if _, checkErr := client.Run(fmt.Sprintf("[ -f %s ]", SoundTouchSdkPrivateCfgOverridePath)); checkErr == nil {
+		if overrideCfg, _ := client.Run(fmt.Sprintf("cat %s", SoundTouchSdkPrivateCfgOverridePath)); overrideCfg != "" {
+			summary.SSHSuccess = true
+			// The untouched factory config at the original path is the OriginalConfig.
+			if origCfg, _ := client.Run(fmt.Sprintf("cat %s", SoundTouchSdkPrivateCfgPath)); origCfg != "" {
+				summary.OriginalConfig = origCfg
+			}
 
-		return overrideCfg, nil
+			return overrideCfg, nil
+		}
 	}
 
 	path := SoundTouchSdkPrivateCfgPath

pkg/service/setup/setup_test.go

@@ -1535,6 +1535,52 @@ func TestCheckIsMigrated(t *testing.T) {
 	})
 }
 
+// TestCheckCurrentConfig_OverrideMissing reproduces issue #214: when the override
+// file does not exist, client.Run returns the cat stderr ("cat: can't open ...")
+// via CombinedOutput. The previous implementation treated that non-empty stderr
+// as a valid config and surfaced it to the UI. Existence must be tested first.
+func TestCheckCurrentConfig_OverrideMissing(t *testing.T) {
+	m := NewManager("http://aftertouch:8000", nil, nil)
+
+	originalCfg := "<SoundTouchSdkPrivateCfg><margeServerUrl>http://streaming.bose.com</margeServerUrl></SoundTouchSdkPrivateCfg>"
+
+	m.NewSSH = func(host string) SSHClient {
+		return &mockSSH{
+			runFunc: func(command string) (string, error) {
+				if command == fmt.Sprintf("[ -f %s ]", SoundTouchSdkPrivateCfgOverridePath) {
+					return "", fmt.Errorf("exit status 1")
+				}
+				if command == fmt.Sprintf("cat %s", SoundTouchSdkPrivateCfgOverridePath) {
+					return fmt.Sprintf("cat: can't open '%s': No such file or directory\n", SoundTouchSdkPrivateCfgOverridePath),
+						fmt.Errorf("exit status 1")
+				}
+				if strings.HasPrefix(command, "[ -f ") && strings.Contains(command, ".original") {
+					return "", fmt.Errorf("exit status 1")
+				}
+				if command == fmt.Sprintf("cat %s", SoundTouchSdkPrivateCfgPath) {
+					return originalCfg, nil
+				}
+				return "", nil
+			},
+		}
+	}
+
+	summary := &MigrationSummary{}
+	cfg, err := m.checkCurrentConfig(summary, "127.0.0.1")
+	if err != nil {
+		t.Fatalf("checkCurrentConfig returned unexpected error: %v", err)
+	}
+	if cfg != originalCfg {
+		t.Errorf("Expected current config to be the original SoundTouchSdkPrivateCfg.xml, got %q", cfg)
+	}
+	if strings.Contains(cfg, "No such file or directory") {
+		t.Errorf("Current config must not contain cat stderr from missing override file: %q", cfg)
+	}
+	if !summary.SSHSuccess {
+		t.Errorf("Expected SSHSuccess to be true when original config is readable")
+	}
+}
+
 func TestMigrateSpeaker_ResolvBlocking(t *testing.T) {
 	tempDir, err := os.MkdirTemp("", "setup-test")
 	if err != nil {