Fix #45: prevent and contain multi-process WebView data-dir crash

app/src/main/java/com/flamyoad/honnoki/MyApplication.kt

@@ -1,7 +1,11 @@
 package com.flamyoad.honnoki
 
 import android.app.Application
+import android.os.Build
+import android.os.Process
+import android.webkit.WebView
 import androidx.appcompat.app.AppCompatDelegate
+import kotlin.system.exitProcess
 import com.flamyoad.honnoki.data.preference.UiPreference
 import com.flamyoad.honnoki.di.*
 import com.github.venom.Venom
@@ -26,6 +30,9 @@ class MyApplication : Application() {
     override fun onCreate() {
         super.onCreate()
 
+        installWebViewMultiProcessGuard()
+        applyWebViewDataDirectorySuffix()
+
         if (BuildConfig.DEBUG) {
             Timber.plant(Timber.DebugTree())
         }
@@ -70,4 +77,82 @@ class MyApplication : Application() {
         venom.initialize(notification)
         Venom.setGlobalInstance(venom)
     }
+
+    /**
+     * Workaround for https://crbug.com/558377 — when the same Android app is launched
+     * in more than one process (e.g. an isolated `:remote` service started by a third
+     * party SDK), the second WebView initialization in the same data directory throws:
+     *
+     *   java.lang.RuntimeException: Using WebView from more than one process at once
+     *   with the same data directory is not supported.
+     *
+     * Setting a per-process suffix before any WebView is touched gives each process
+     * its own data directory and avoids the crash. Available since API 28 (P).
+     *
+     * Tracking issue: https://github.com/flamyoad/Honnoki/issues/45
+     */
+    private fun applyWebViewDataDirectorySuffix() {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.P) return
+        val processName = getProcessName() ?: return
+        if (packageName != processName) {
+            try {
+                WebView.setDataDirectorySuffix(processName)
+            } catch (t: Throwable) {
+                Timber.w(t, "Failed to set WebView data directory suffix for %s", processName)
+            }
+        }
+    }
+
+    /**
+     * Belt-and-suspenders for https://crbug.com/558377. The data-directory suffix
+     * above prevents the collision when two processes have *different* names, but
+     * the same `RuntimeException` can also be triggered by:
+     *
+     *   - a stale data-dir lock left over from a previously-killed instance of
+     *     this same process (the lock owner PID is gone but the file lock remains);
+     *   - the system swapping the WebView provider implementation while we're
+     *     running, causing two AwBrowserProcess attempts in quick succession.
+     *
+     * In both cases the suffix can't help. Letting the exception propagate kills
+     * the app with a user-visible "App keeps stopping" dialog and a Crashlytics
+     * report (issue #45). Instead we install a fallback handler that recognises
+     * this exact exception, logs it, and silently terminates the current process.
+     * Android's ActivityManager will restart any foreground component cleanly,
+     * by which time the lock will have been released by the OS.
+     *
+     * The handler is intentionally narrow — it only swallows the WebView
+     * multi-process exception. Every other crash is forwarded to the previous
+     * default handler (Crashlytics, etc.) untouched.
+     */
+    private fun installWebViewMultiProcessGuard() {
+        val previous = Thread.getDefaultUncaughtExceptionHandler()
+        Thread.setDefaultUncaughtExceptionHandler { thread, throwable ->
+            if (isWebViewMultiProcessCrash(throwable)) {
+                Timber.w(
+                    throwable,
+                    "Swallowing WebView multi-process data-dir crash; killing pid %d to release the lock",
+                    Process.myPid()
+                )
+                Process.killProcess(Process.myPid())
+                exitProcess(10)
+            } else {
+                previous?.uncaughtException(thread, throwable)
+            }
+        }
+    }
+
+    private fun isWebViewMultiProcessCrash(throwable: Throwable?): Boolean {
+        var t: Throwable? = throwable
+        while (t != null) {
+            val msg = t.message
+            if (t is RuntimeException &&
+                msg != null &&
+                msg.contains("Using WebView from more than one process")
+            ) {
+                return true
+            }
+            t = t.cause
+        }
+        return false
+    }
 }