fix(car): notification-only car messaging for production; park templated behind flag (#6015)

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

androidApp/build.gradle.kts

@@ -43,9 +43,24 @@ if (keystorePropertiesFile.exists()) {
     keystorePropertiesFile.inputStream().use { keystoreProperties.load(it) }
 }
 
+// The templated Android Auto experience (CarAppService + HomeScreen) is a Google "templated
+// messaging" beta feature that is publishable only to Closed/Internal tracks — Open/Production
+// submissions are auto-rejected (https://developer.android.com/training/cars/communication/templated-messaging).
+// Default builds therefore ship *notification-only* car messaging, which is GA and production-safe.
+// Build a Closed-track templated AAB with: -PenableCarTemplates=true
+// ponytail: gated by a gradle property + res override, not a full build flavor — templated is
+// parked until it leaves Google's beta. Promote to a flavor dimension only if CI must ship both.
+val enableCarTemplates = (findProperty("enableCarTemplates") as String?)?.toBoolean() ?: false
+
 configure<ApplicationExtension> {
     namespace = "org.meshtastic.app"
 
+    // When templates are enabled, this res dir overrides feature:car's notification-only
+    // automotive_app_desc.xml with one that also declares <uses name="template" />.
+    if (enableCarTemplates) {
+        sourceSets.getByName("google").res.srcDir("src/googleCarTemplates/res")
+    }
+
     signingConfigs {
         create("release") {
             keyAlias = keystoreProperties["keyAlias"] as String?
@@ -115,6 +130,10 @@ configure<ApplicationExtension> {
         }
         ndk { abiFilters += listOf("armeabi-v7a", "arm64-v8a") }
 
+        // Activates the (google-only) CarAppService. Off by default so production builds ship
+        // notification-only car messaging; flipped on by -PenableCarTemplates=true for Closed tracks.
+        manifestPlaceholders["carTemplatesEnabled"] = enableCarTemplates.toString()
+
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
     }
 

androidApp/src/googleCarTemplates/res/xml/automotive_app_desc.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Templated Android Auto declaration, included ONLY when building with -PenableCarTemplates=true
+  (wired in androidApp/build.gradle.kts). Being an app-module resource, it overrides feature:car's
+  notification-only automotive_app_desc.xml in the merge, adding <uses name="template" /> so Android
+  Auto recognizes and launches the CarAppService/HomeScreen. Closed/Internal tracks only — Google
+  auto-rejects templated-messaging builds submitted to Open/Production.
+-->
+<automotiveApp>
+    <uses name="notification" />
+    <uses name="template" />
+</automotiveApp>

feature/car/build.gradle.kts

@@ -30,6 +30,11 @@ android {
     defaultConfig {
         minSdk = 23
         consumerProguardFiles("proguard-rules.pro")
+        // The CarAppService is disabled unless -PenableCarTemplates=true. feature:car resolves the
+        // placeholder in its OWN manifest, so it must read the property directly (the app's value does
+        // not override a library's own placeholder). Default false → production ships it disabled.
+        manifestPlaceholders["carTemplatesEnabled"] =
+            ((findProperty("enableCarTemplates") as String?)?.toBoolean() ?: false).toString()
     }
 
     // Robolectric provides the Android context that androidx.car.app TestCarContext/ScreenController need.

feature/car/src/main/AndroidManifest.xml

@@ -2,8 +2,13 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
 
     <application>
+        <!-- enabled is gated by the app's `carTemplatesEnabled` manifest placeholder: off by default
+             (production ships notification-only car messaging), on for -PenableCarTemplates=true builds.
+             The decisive gate is automotive_app_desc's <uses name="template" /> (see res/xml); this is
+             defense-in-depth so the templated service can't be bound in production. -->
         <service
             android:name="org.meshtastic.feature.car.service.MeshtasticCarAppService"
+            android:enabled="${carTemplatesEnabled}"
             android:exported="true"
             android:permission="androidx.car.app.CarAppService">
             <intent-filter>

feature/car/src/main/kotlin/org/meshtastic/feature/car/screens/HomeScreen.kt

@@ -144,8 +144,22 @@ class HomeScreen(
         carContext.getCarService(AppManager::class.java).showAlert(alert)
     }
 
+    // Any exception thrown out of onGetTemplate() crashes the Android Auto host ("content not able to
+    // load") and fails Play's Auto review. Degrade to a safe template instead and log for diagnosis.
+    // NOTE: this guards exceptions in OUR build path; a host-side template-contract rejection (e.g. the
+    // messaging surface must be a ListTemplate/SectionedItemTemplate of ConversationItems, not this
+    // TabTemplate dashboard) would not throw here — confirm against the Play pre-launch stack before
+    // promoting templated builds. See -PenableCarTemplates in androidApp/build.gradle.kts.
+    @Suppress("TooGenericExceptionCaught")
+    override fun onGetTemplate(): Template = try {
+        buildHomeTemplate()
+    } catch (e: Exception) {
+        Logger.e(tag = "HomeScreen", throwable = e) { "onGetTemplate failed; showing fallback template" }
+        buildDisconnectedTemplate()
+    }
+
     @Suppress("ReturnCount")
-    override fun onGetTemplate(): Template {
+    private fun buildHomeTemplate(): Template {
         val connectionStatus = stateCoordinator.sessionState.value.connectionStatus
         if (connectionStatus == ConnectionState.Disconnected || connectionStatus == ConnectionState.DeviceSleep) {
             return buildDisconnectedTemplate()

feature/car/src/main/res/xml/automotive_app_desc.xml

@@ -1,5 +1,10 @@
 <?xml version="1.0" encoding="utf-8"?>
+<!--
+  Default (production) declaration: notification-only car messaging. This is GA and ships to any
+  Play track. The templated experience (<uses name="template" />) is a Google beta restricted to
+  Closed/Internal tracks, so it is added ONLY by androidApp/src/googleCarTemplates/res when built
+  with -PenableCarTemplates=true (that override replaces this file in the merge).
+-->
 <automotiveApp>
-    <uses name="template" />
     <uses name="notification" />
 </automotiveApp>