fix: Logic error in MemoryCache.setValue() (#2931)

Fixes a logic error which prevented values in `MemoryCache` from being
updated when calling `setValue` with a preexisting `key`.


Replace or remove this text.

packages/flame/lib/src/cache/memory_cache.dart

@@ -1,17 +1,20 @@
 import 'dart:collection';
 
 /// Simple class to cache values with size based eviction.
-///
 class MemoryCache<K, V> {
   final LinkedHashMap<K, V> _cache = LinkedHashMap();
   final int cacheSize;
 
   MemoryCache({this.cacheSize = 10});
 
+  /// Adds the [value] to the cache under [key].
+  ///
+  /// If that [key] is already used, updates the value.
   void setValue(K key, V value) {
-    if (!_cache.containsKey(key)) {
-      _cache[key] = value;
+    final preexisting = _cache.containsKey(key);
+    _cache[key] = value;
 
+    if (!preexisting) {
       while (_cache.length > cacheSize) {
         final k = _cache.keys.first;
         _cache.remove(k);
@@ -29,11 +32,15 @@ class MemoryCache<K, V> {
     _cache.clear();
   }
 
+  /// Gets the value under [key].
   V? getValue(K key) => _cache[key];
 
+  /// Checks whether the cache has any value under [key].
   bool containsKey(K key) => _cache.containsKey(key);
 
+  /// Returns the number of values saved in this memory cache.
   int get size => _cache.length;
 
+  /// Iterates over all existing keys with values.
   Iterable<K> get keys => _cache.keys;
 }

packages/flame/test/cache/memory_cache_test.dart

@@ -18,6 +18,14 @@ void main() {
       expect(cache.keys.length, 1);
     });
 
+    test('updates key', () {
+      final cache = MemoryCache<int, String>();
+      cache.setValue(0, 'bla');
+      expect(cache.getValue(0), 'bla');
+      cache.setValue(0, 'ble');
+      expect(cache.getValue(0), 'ble');
+    });
+
     test('cache size', () {
       final cache = MemoryCache<int, String>(cacheSize: 1);
       cache.setValue(0, 'bla');