fix: used `initialPosition` in `BodyDef` (#52)

* fix: using BodyDef

* feat: included test

* refactor: removed TODO

lib/game/components/ball.dart

@@ -39,6 +39,7 @@ class Ball extends BodyComponent<PinballGame> with InitialPosition {
     final fixtureDef = FixtureDef(shape)..density = 1;
 
     final bodyDef = BodyDef()
+      ..position = initialPosition
       ..userData = this
       ..type = BodyType.dynamic;
 

lib/game/components/baseboard.dart

@@ -58,7 +58,7 @@ class Baseboard extends BodyComponent with InitialPosition {
     const angle = math.pi / 7;
 
     final bodyDef = BodyDef()
-      ..type = BodyType.static
+      ..position = initialPosition
       ..angle = _side.isLeft ? -angle : angle;
 
     final body = world.createBody(bodyDef);

lib/game/components/bonus_word.dart

@@ -129,6 +129,7 @@ class BonusLetter extends BodyComponent<PinballGame>
     final fixtureDef = FixtureDef(shape)..isSensor = true;
 
     final bodyDef = BodyDef()
+      ..position = initialPosition
       ..userData = this
       ..type = BodyType.static;
 

lib/game/components/flipper.dart

@@ -189,6 +189,7 @@ class Flipper extends BodyComponent with KeyboardHandler, InitialPosition {
   @override
   Body createBody() {
     final bodyDef = BodyDef()
+      ..position = initialPosition
       ..gravityScale = 0
       ..type = BodyType.dynamic;
     final body = world.createBody(bodyDef);

lib/game/components/initial_position.dart

@@ -24,6 +24,11 @@ mixin InitialPosition<T extends Forge2DGame> on BodyComponent<T> {
   @override
   Future<void> onLoad() async {
     await super.onLoad();
-    body.position.setFrom(initialPosition);
+    // TODO(alestiago): Investiagate why body.position.setFrom(initialPosition)
+    // works for some components and not others.
+    assert(
+      body.position == initialPosition,
+      'Body position does not match initialPosition.',
+    );
   }
 }

lib/game/components/joint_anchor.dart

@@ -22,6 +22,7 @@ class JointAnchor extends BodyComponent with InitialPosition {
 
   @override
   Body createBody() {
-    return world.createBody(BodyDef());
+    final bodyDef = BodyDef()..position = initialPosition;
+    return world.createBody(bodyDef);
   }
 }

lib/game/components/pathway.dart

@@ -148,7 +148,7 @@ class Pathway extends BodyComponent with InitialPosition {
 
   @override
   Body createBody() {
-    final bodyDef = BodyDef()..type = BodyType.static;
+    final bodyDef = BodyDef()..position = initialPosition;
     final body = world.createBody(bodyDef);
     for (final path in _paths) {
       final chain = ChainShape()

lib/game/components/plunger.dart

@@ -25,6 +25,7 @@ class Plunger extends BodyComponent with KeyboardHandler, InitialPosition {
     final fixtureDef = FixtureDef(shape)..density = 5;
 
     final bodyDef = BodyDef()
+      ..position = initialPosition
       ..userData = this
       ..type = BodyType.dynamic
       ..gravityScale = 0;

lib/game/components/round_bumper.dart

@@ -27,7 +27,7 @@ class RoundBumper extends BodyComponent with ScorePoints, InitialPosition {
 
     final fixtureDef = FixtureDef(shape)..restitution = 1;
 
-    final bodyDef = BodyDef()..type = BodyType.static;
+    final bodyDef = BodyDef()..position = initialPosition;
 
     return world.createBody(bodyDef)..createFixture(fixtureDef);
   }

lib/game/components/sling_shot.dart

@@ -83,7 +83,8 @@ class SlingShot extends BodyComponent with InitialPosition {
 
   @override
   Body createBody() {
-    final body = world.createBody(BodyDef());
+    final bodyDef = BodyDef()..position = initialPosition;
+    final body = world.createBody(bodyDef);
     _createFixtureDefs().forEach(body.createFixture);
 
     return body;

test/game/components/initial_position_test.dart

@@ -12,6 +12,13 @@ class TestBodyComponent extends BodyComponent with InitialPosition {
   }
 }
 
+class TestPositionedBodyComponent extends BodyComponent with InitialPosition {
+  @override
+  Body createBody() {
+    return world.createBody(BodyDef()..position = initialPosition);
+  }
+}
+
 void main() {
   final flameTester = FlameTester(Forge2DGame.new);
   group('InitialPosition', () {
@@ -20,11 +27,27 @@ void main() {
       expect(component.initialPosition, Vector2(1, 2));
     });
 
+    flameTester.test(
+      'throws AssertionError '
+      'when BodyDef is not positioned with initialPosition',
+      (game) async {
+        final component = TestBodyComponent()
+          ..initialPosition = Vector2.all(
+            10,
+          );
+        await expectLater(
+          () => game.ensureAdd(component),
+          throwsAssertionError,
+        );
+      },
+    );
+
     flameTester.test(
       'positions correctly',
       (game) async {
         final position = Vector2.all(10);
-        final component = TestBodyComponent()..initialPosition = position;
+        final component = TestPositionedBodyComponent()
+          ..initialPosition = position;
         await game.ensureAdd(component);
         expect(component.body.position, equals(position));
       },