From 0b8e3f3071ebcb3b209620cd45ca56bbfbf41e49 Mon Sep 17 00:00:00 2001
From: Marcus Hoffmann <bubu@bubu1.eu>
Date: Fri, 2 Jul 2021 12:17:05 +0200
Subject: [PATCH] make tryGet* safer

* check casts (for list and map) at cast time by recreating the list/map
  instead of throwing on access.
* type warnings work now slightly differently:
  * when we expect nullable fields to be actually null within normal
    operation you can explicitly set the tryGet type param to an
optional type and mute the warning. Otherwise it'll warn that something
is null which we expect to something else.
---
 .../model/events/room_encrypted_content.dart  |  4 +-
 lib/src/utils/try_get_map_extension.dart      | 41 ++++++++++---------
 2 files changed, 24 insertions(+), 21 deletions(-)

diff --git a/lib/src/model/events/room_encrypted_content.dart b/lib/src/model/events/room_encrypted_content.dart
index b53c561c..060c328e 100644
--- a/lib/src/model/events/room_encrypted_content.dart
+++ b/lib/src/model/events/room_encrypted_content.dart
@@ -47,8 +47,8 @@ class RoomEncryptedContent {
   RoomEncryptedContent.fromJson(Map<String, dynamic> json)
       : algorithm = json.tryGet('algorithm') ?? '',
         senderKey = json.tryGet('sender_key') ?? '',
-        deviceId = json.tryGet('device_id'),
-        sessionId = json.tryGet('session_id'),
+        deviceId = json.tryGet<String?>('device_id'),
+        sessionId = json.tryGet<String?>('session_id'),
         ciphertextMegolm = json.silentTryGet('ciphertext'),
         // filter out invalid/incomplete CiphertextInfos
         ciphertextOlm = json
diff --git a/lib/src/utils/try_get_map_extension.dart b/lib/src/utils/try_get_map_extension.dart
index fe6a9d4d..41d0c768 100644
--- a/lib/src/utils/try_get_map_extension.dart
+++ b/lib/src/utils/try_get_map_extension.dart
@@ -21,15 +21,16 @@
 * SOFTWARE.
 */
 
+import 'dart:core';
+
 import 'logs.dart';
 
 extension TryGetMapExtension on Map<String, dynamic> {
-  T? tryGet<T extends Object>(String key) {
-    final value = this[key];
-    if (value != null && !(value is T)) {
+  T? tryGet<T extends Object?>(String key) {
+    final Object? value = this[key];
+    if (value is! T) {
       Logs().w(
-          'Expected "${T.runtimeType}" in event content for the Key "$key" but got "${value.runtimeType}".',
-          StackTrace.current);
+          'Expected "$T" in event content for the Key "$key" but got "${value.runtimeType}".');
       return null;
     }
     return value;
@@ -37,43 +38,45 @@ extension TryGetMapExtension on Map<String, dynamic> {
 
   /// Same as tryGet but without logging any warnings.
   /// This is helpful if you have a field that can mean multiple things on purpose.
-  T? silentTryGet<T extends Object>(String key) {
-    final value = this[key];
-    if (value != null && !(value is T)) {
+  T? silentTryGet<T extends Object?>(String key) {
+    final Object? value = this[key];
+    if (value is! T) {
       return null;
     }
     return value;
   }
 
   List<T>? tryGetList<T>(String key) {
-    final value = this[key];
-    if (value != null && !(value is List)) {
+    final Object? value = this[key];
+    if (value is! List) {
       Logs().w(
-          'Expected "List<${T.runtimeType}>" in event content for the key "$key" but got "${value.runtimeType}".',
+          'Expected "List<$T>" in event content for the key "$key" but got "${value.runtimeType}".',
           StackTrace.current);
       return null;
     }
     try {
-      return (value as List).cast<T>();
+      // copy entries to ensure type check failures here and not an access
+      return value.cast<T>().toList();
     } catch (_) {
-      Logs().w(
-          'Unable to create "List<${T.runtimeType}>" in event content for the key "$key"');
+      Logs()
+          .w('Unable to create "List<$T>" in event content for the key "$key"');
       return null;
     }
   }
 
   Map<A, B>? tryGetMap<A, B>(String key) {
-    final value = this[key];
-    if (value != null && !(value is Map)) {
+    final Object? value = this[key];
+    if (value is! Map) {
       Logs().w(
-          'Expected "Map<${A.runtimeType},${B.runtimeType}>" in event content for the key "$key" but got "${value.runtimeType}".');
+          'Expected "Map<$A,$B>" in event content for the key "$key" but got "${value.runtimeType}".');
       return null;
     }
     try {
-      return (value as Map).cast<A, B>();
+      // copy map to ensure type check failures here and not an access
+      return Map.from(value.cast<A, B>());
     } catch (_) {
       Logs().w(
-          'Unable to create "Map<${A.runtimeType},${B.runtimeType}>" in event content for the key "$key"');
+          'Unable to create "Map<$A,$B>" in event content for the key "$key"');
       return null;
     }
   }