fix(android): MM-68210 guard WebSocket methods against missing client NPE

android/src/main/java/com/mattermost/networkclient/ApiClientModuleImpl.kt

@@ -160,8 +160,13 @@ class ApiClientModuleImpl(appContext: Context) {
             return promise.reject(error)
         }
 
+        val client = clients[url]
+        if (client == null) {
+            return promise.reject(Error("Client not found for baseUrl: $url"))
+        }
+
         try {
-            promise.resolve(clients[url]!!.clientHeaders)
+            promise.resolve(client.clientHeaders)
         } catch (error: Exception) {
             promise.reject(error)
         }
@@ -175,8 +180,13 @@ class ApiClientModuleImpl(appContext: Context) {
             return promise.reject(error)
         }
 
+        val client = clients[url]
+        if (client == null) {
+            return promise.reject(Error("Client not found for baseUrl: $url"))
+        }
+
         try {
-            clients[url]!!.addClientHeaders(headers)
+            client.addClientHeaders(headers)
             promise.resolve(null)
         } catch (error: Exception) {
             promise.reject(error)
@@ -191,8 +201,13 @@ class ApiClientModuleImpl(appContext: Context) {
             return promise.reject(error)
         }
 
+        val client = clients[url]
+        if (client == null) {
+            return promise.reject(Error("Client not found for baseUrl: $url"))
+        }
+
         try {
-            clients[url]!!.importClientP12AndRebuildClient(path, password)
+            client.importClientP12AndRebuildClient(path, password)
             promise.resolve(null)
         } catch (error: Exception) {
             promise.reject(error)
@@ -207,8 +222,13 @@ class ApiClientModuleImpl(appContext: Context) {
             return promise.reject(error)
         }
 
+        val client = clients[url]
+        if (client == null) {
+            return promise.reject(Error("Client not found for baseUrl: $url"))
+        }
+
         try {
-            clients[url]!!.invalidate()
+            client.invalidate()
             clients.remove(url)
             promise.resolve(null)
         } catch (error: Exception) {
@@ -254,7 +274,11 @@ class ApiClientModuleImpl(appContext: Context) {
             return promise.reject(Error("Couldn't create dir: " + parent.path))
         }
 
-        val client = clients[url]!!
+        val client = clients[url]
+        if (client == null) {
+            return promise.reject(Error("Client not found for baseUrl: $url"))
+        }
+
         val downloadCall = client.buildDownloadCall(endpoint, taskId, options)
         calls[taskId] = downloadCall
 
@@ -314,7 +338,11 @@ class ApiClientModuleImpl(appContext: Context) {
             return promise.reject(error)
         }
 
-        val client = clients[url]!!
+        val client = clients[url]
+        if (client == null) {
+            return promise.reject(Error("Client not found for baseUrl: $url"))
+        }
+
         val uploadCall = client.buildUploadCall(endpoint, filePath, taskId, options)
         calls[taskId] = uploadCall
 

android/src/main/java/com/mattermost/networkclient/WebSocketClientModuleImpl.kt

@@ -44,8 +44,8 @@ class WebSocketClientModuleImpl(reactApplicationContext: ReactApplicationContext
             return promise.reject(error)
         }
 
-        if (clients.containsKey(wsUri)) {
-            clients[wsUri]!!.webSocket?.close(1000, null)
+        clients[wsUri]?.let { client ->
+            client.webSocket?.close(1000, null)
             clients.remove(wsUri)
         }
 
@@ -82,9 +82,10 @@ class WebSocketClientModuleImpl(reactApplicationContext: ReactApplicationContext
             return promise.reject(error)
         }
 
-
-        clients[wsUri]!!.webSocket?.close(1000, null)
-        clients.remove(wsUri)
+        clients[wsUri]?.let { client ->
+            client.webSocket?.close(1000, null)
+            clients.remove(wsUri)
+        }
 
         promise.resolve(null)
     }
@@ -97,8 +98,13 @@ class WebSocketClientModuleImpl(reactApplicationContext: ReactApplicationContext
             return promise.reject(error)
         }
 
+        val client = clients[wsUri]
+        if (client == null) {
+            return promise.reject("WebSocket error", "no client for this websocket url")
+        }
+
         try {
-            clients[wsUri]!!.createWebSocket()
+            client.createWebSocket()
             promise.resolve(null)
         } catch (error: Exception) {
             promise.reject(error)
@@ -113,8 +119,13 @@ class WebSocketClientModuleImpl(reactApplicationContext: ReactApplicationContext
             return promise.reject(error)
         }
 
+        val client = clients[wsUri]
+        if (client == null) {
+            return promise.reject("WebSocket error", "no client for this websocket url")
+        }
+
         try {
-            clients[wsUri]!!.webSocket!!.cancel()
+            client.webSocket?.cancel()
             promise.resolve(null)
         } catch (error: Exception) {
             promise.reject(error)
@@ -130,9 +141,18 @@ class WebSocketClientModuleImpl(reactApplicationContext: ReactApplicationContext
         }
 
 
+        val client = clients[wsUri]
+        if (client == null) {
+            return promise.reject("WebSocket error", "no client for this websocket url")
+        }
+
         try {
-            clients[wsUri]!!.webSocket!!.send(data)
-            promise.resolve(null)
+            val sent = client.webSocket?.send(data)
+            if (sent == true) {
+                promise.resolve(null)
+            } else {
+                promise.reject("WebSocket error", "websocket is not connected or failed to send data")
+            }
         } catch (error: Exception) {
             promise.reject(error)
         }

android/src/test/java/com/mattermost/networkclient/WebSocketClientNullSafetyTest.kt

@@ -0,0 +1,56 @@
+package com.mattermost.networkclient
+
+import org.junit.Assert.assertNull
+import org.junit.Assert.fail
+import org.junit.Test
+
+/**
+ * Reproduces Sentry #7153287556: NullPointerException when accessing a
+ * map entry that doesn't exist using Kotlin's force-unwrap operator (!!).
+ *
+ * WebSocketClientModuleImpl stores clients in a MutableMap<URI, NetworkClient>.
+ * The old code used clients[wsUri]!! which crashes when the URI isn't in the map.
+ * The fix uses clients[wsUri]?.let { ... } for safe access.
+ */
+class WebSocketClientNullSafetyTest {
+
+    /**
+     * Demonstrates the crash: force-unwrap (!!) on a missing map key throws
+     * KotlinNullPointerException. This is exactly what happened in
+     * invalidateClientFor() before the fix.
+     */
+    @Test(expected = NullPointerException::class)
+    fun forceUnwrap_onMissingMapKey_throwsNPE() {
+        val clients = mutableMapOf<String, String>()
+
+        // Old pattern: clients[key]!! — crashes when key doesn't exist
+        clients["ws://nonexistent"]!!
+    }
+
+    /**
+     * The fix: safe access with ?.let returns null instead of crashing.
+     * invalidateClientFor should be idempotent — invalidating a
+     * non-existent client is not an error.
+     */
+    @Test
+    fun safeAccess_onMissingMapKey_returnsNull() {
+        val clients = mutableMapOf<String, String>()
+
+        // New pattern: clients[key]?.let { ... } — no crash
+        val result = clients["ws://nonexistent"]?.let { it }
+        assertNull(result)
+    }
+
+    /**
+     * Verifies that safe access still works correctly when the key exists.
+     */
+    @Test
+    fun safeAccess_onExistingMapKey_returnsValue() {
+        val clients = mutableMapOf<String, String>()
+        clients["ws://example.com"] = "client"
+
+        var accessed = false
+        clients["ws://example.com"]?.let { accessed = true }
+        assert(accessed) { "Expected ?.let block to execute for existing key" }
+    }
+}