fix!: support parsing empty tile terrain values (#61)

Author: devoncarew

packages/tiled/lib/src/tileset/tile.dart

@@ -24,7 +24,7 @@ class Tile {
   double probability;
 
   /// List of indexes of the terrain.
-  List<int> terrain;
+  List<int?> terrain;
 
   TiledImage? image;
   Layer? objectGroup;
@@ -60,7 +60,7 @@ class Tile {
           terrain: parser
                   .getStringOrNull('terrain')
                   ?.split(',')
-                  .map(int.parse)
+                  .map((str) => str.isEmpty ? null : int.parse(str))
                   .toList() ??
               [],
           image: parser.getSingleChildOrNullAs('image', TiledImage.parse),

packages/tiled/test/fixtures/map_with_empty_terrains.tmx

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<map version="1.0" orientation="orthogonal" renderorder="right-down" width="32" height="32" tilewidth="16" tileheight="16" nextobjectid="1">
+ <tileset firstgid="1" name="test tileset" tilewidth="16" tileheight="16" tilecount="256" columns="16">
+  <image source="tileset_16x16.png" width="256" height="256"/>
+  <terraintypes>
+   <terrain name="test bright" tile="2"/>
+   <terrain name="test normal" tile="50"/>
+   <terrain name="test dark" tile="98"/>
+  </terraintypes>
+  <tile id="0" terrain=",,,0"/>
+  <tile id="1" terrain="0,0,0,"/>
+  <tile id="2" terrain="0,0,,"/>
+  <tile id="3" terrain="0,0,,0"/>
+  <tile id="4" terrain=",,,0"/>
+  <tile id="5" terrain=",,0,"/>
+  <tile id="50" terrain="1,1,,"/>
+  <tile id="98" terrain="2,2,,"/>
+ </tileset>
+</map>

packages/tiled/test/parser_test.dart

@@ -373,6 +373,18 @@ void main() {
       );
     });
   });
+
+  group('Parser tiles', () {
+    test('support empty terrain values', () {
+      final xml = File('./test/fixtures/map_with_empty_terrains.tmx')
+          .readAsStringSync();
+      final tiledMap = TileMapParser.parseTmx(xml);
+
+      final tileset = tiledMap.tilesets.first;
+      final tile = tileset.tiles.first;
+      expect(tile.terrain, anyElement(isNull));
+    });
+  });
 }
 
 class CustomTsxProvider extends TsxProvider {