replace cache getter with evictFromCache method for CachedAssetReader

Author: jakemac53

lib/src/asset/cache.dart

@@ -40,18 +40,23 @@ class AssetCache {
 /// will first look up values in the [AssetCache], and if not present it will
 /// use the [AssetReader] and add the [Asset] to the [AssetCache].
 class CachedAssetReader extends AssetReader {
-  final AssetCache cache;
+  final AssetCache _cache;
   final AssetReader _reader;
   /// Cache of ongoing reads by [AssetId].
   final _pendingReads = <AssetId, Future<String>>{};
   /// Cache of ongoing hasInput checks by [AssetId].
   final _pendingHasInputChecks = <AssetId, Future<bool>>{};
 
-  CachedAssetReader(this.cache, this._reader);
+  CachedAssetReader(this._cache, this._reader);
+
+  /// Evicts [id] from the underlying cache.
+  void evictFromCache(AssetId id) {
+    _cache.remove(id);
+  }
 
   @override
   Future<bool> hasInput(AssetId id) {
-    if (cache.contains(id)) return new Future.value(true);
+    if (_cache.contains(id)) return new Future.value(true);
 
     _pendingHasInputChecks.putIfAbsent(id, () async {
       var exists = await _reader.hasInput(id);
@@ -63,13 +68,13 @@ class CachedAssetReader extends AssetReader {
 
   @override
   Future<String> readAsString(AssetId id, {Encoding encoding: UTF8}) {
-    if (cache.contains(id)) {
-      return new Future.value(cache.get(id).stringContents);
+    if (_cache.contains(id)) {
+      return new Future.value(_cache.get(id).stringContents);
     }
 
     _pendingReads.putIfAbsent(id, () async {
       var content = await _reader.readAsString(id, encoding: encoding);
-      cache.put(new Asset(id, content));
+      _cache.put(new Asset(id, content));
       _pendingReads.remove(id);
       return content;
     });

lib/src/generate/build_impl.dart

@@ -148,7 +148,7 @@ class BuildImpl {
       var node = _assetGraph.get(id);
       if (node == null) return;
       if (_reader is CachedAssetReader) {
-        (_reader as CachedAssetReader).cache.remove(id);
+        (_reader as CachedAssetReader).evictFromCache(id);
       }
 
       /// Update all ouputs of this asset as well.