fix: current_position.json保留所有data_name，无持仓时显示size=0/price=0

- 恢复 _write_current_position 保留所有数据源的仓位记录
- 无持仓的数据源显示 size=0, price=0.0
- 更新测试
- 全部 497 个测试通过

Author: cloudQuant

backtrader/observers/tradelogger.py

@@ -312,14 +312,12 @@ def _write_run_info(self):
             json.dump(run_info, f, indent=2, ensure_ascii=False, default=str)
 
     def _write_current_position(self, positions):
-        """Overwrite current_position.json with latest non-zero positions only."""
+        """Overwrite current_position.json with latest positions for all data feeds."""
         if self._log_dir is None or not self.p.log_file_enabled:
             return
         path = os.path.join(self._log_dir, "current_position.json")
         serializable = []
         for p in positions:
-            if p.get("size", 0) == 0:
-                continue
             row = {}
             for k, v in p.items():
                 row[k] = self._format_value(v) if isinstance(v, dt_module.datetime) else v

tests/add_tests/test_observer_tradelogger.py

@@ -372,9 +372,7 @@ def test_file_output_log_format():
         with open(pos_path, "r") as f:
             positions = json.load(f)
         assert isinstance(positions, list)
-        # Only non-zero positions should be in the file
-        for p in positions:
-            assert p["size"] != 0
+        assert len(positions) >= 1
     finally:
         shutil.rmtree(tmp_dir, ignore_errors=True)
 
@@ -409,7 +407,7 @@ def test_file_output_csv_format():
 
 
 def test_current_position_json():
-    """Verify current_position.json only contains non-zero positions."""
+    """Verify current_position.json contains all data feeds with valid structure."""
     tmp_dir = tempfile.mkdtemp()
     try:
         cerebro, strat = _create_cerebro(observer_kwargs=dict(
@@ -425,15 +423,11 @@ def test_current_position_json():
         with open(pos_path, "r") as f:
             positions = json.load(f)
         assert isinstance(positions, list)
-        # All entries in current_position.json must have non-zero size
+        assert len(positions) >= 1
         for p in positions:
             assert "data_name" in p
             assert "size" in p
             assert "price" in p
-            assert p["size"] != 0, (
-                f"current_position.json should only contain non-zero positions, "
-                f"got size=0 for {p.get('data_name')}"
-            )
     finally:
         shutil.rmtree(tmp_dir, ignore_errors=True)