From da5669e1dfaf2c0b3e7841b6127fa6ec2f7f8a59 Mon Sep 17 00:00:00 2001
From: Kristoffer Dalby <kristoffer@dalby.cc>
Date: Mon, 28 Sep 2026 14:35:17 +0000
Subject: [PATCH] android: make HealthNotifier init-order test fail on the NPE

headscale's Android emulator integration tests (juanfont/headscale#3488)
hit this NPE on 1.102.4, which predates the #835 fix. Reproducing it
here showed constructionWithNonRunningStateDoesNotCrash (#835) still
passes with currentWarnings declared after init again. The NPE is
thrown in a launched coroutine with no handler, so it goes to the
thread's uncaught handler, which only prints on the JVM (on Android it
kills the process). Capture it via CoroutineExceptionHandler and
rethrow.

Updates tailscale/corp#46191

Signed-off-by: Kristoffer Dalby <kristoffer@dalby.cc>
---
 .../tailscale/ipn/ui/notifier/HealthNotifierTest.kt    | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/android/src/test/kotlin/com/tailscale/ipn/ui/notifier/HealthNotifierTest.kt b/android/src/test/kotlin/com/tailscale/ipn/ui/notifier/HealthNotifierTest.kt
index 8fb2c4e086..b14b719fd5 100644
--- a/android/src/test/kotlin/com/tailscale/ipn/ui/notifier/HealthNotifierTest.kt
+++ b/android/src/test/kotlin/com/tailscale/ipn/ui/notifier/HealthNotifierTest.kt
@@ -10,6 +10,7 @@ import com.tailscale.ipn.ui.model.Health.UnhealthyState
 import com.tailscale.ipn.ui.model.Ipn
 import com.tailscale.ipn.util.TSLog
 import com.tailscale.ipn.util.TSLog.LibtailscaleWrapper
+import kotlinx.coroutines.CoroutineExceptionHandler
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.ExperimentalCoroutinesApi
@@ -131,15 +132,20 @@ class HealthNotifierTest {
    * immediately calls dropAllWarnings() (reading currentWarnings) when the initial ipn state is not
    * Running. If currentWarnings/currentIcon are declared after the init block, that read hits a
    * null StateFlow and NPEs. Using Dispatchers.Unconfined runs the launched coroutine eagerly
-   * inside the constructor, deterministically reproducing the race on the old ordering.
+   * inside the constructor, deterministically reproducing the race on the old ordering. The NPE
+   * surfaces as an uncaught coroutine exception, which kills the process on Android but only gets
+   * printed on the JVM, so it must be captured explicitly for the test to fail.
    */
   @Test
   fun constructionWithNonRunningStateDoesNotCrash() {
-    val scope = CoroutineScope(Dispatchers.Unconfined)
+    var uncaught: Throwable? = null
+    val scope =
+        CoroutineScope(Dispatchers.Unconfined + CoroutineExceptionHandler { _, e -> uncaught = e })
     try {
       val healthFlow = MutableStateFlow<Health.State?>(healthState(derpWarning()))
       val ipnFlow = MutableStateFlow(Ipn.State.Stopped)
       val notifier = HealthNotifier(healthFlow, ipnFlow, scope)
+      uncaught?.let { throw it }
       assertTrue(notifier.currentWarnings.value.isEmpty())
       assertNull(notifier.currentIcon.value)
     } finally {