feat: 数据集加载时校验必填字段

- BaseDataset.required_keys 属性声明所需存储 key
- load() 时自动校验，缺失立即抛 KeyError
- SEQ/SFT/DPO/GRPO 各自声明 required_keys

astrai/dataset/dataset.py

@@ -28,6 +28,26 @@ class BaseDataset(Dataset, ABC):
         self.stride = stride
         self.storage: Optional[BaseStorage] = None
 
+    @property
+    def required_keys(self) -> List[str]:
+        """Return required storage keys for this dataset type.
+
+        Subclasses should override to specify expected keys.
+        """
+        return []
+
+    def _validate_keys(self):
+        if not self.required_keys:
+            return
+        actual_keys = set(self.storage.keys)
+        missing = [k for k in self.required_keys if k not in actual_keys]
+        if missing:
+            raise KeyError(
+                f"Dataset {type(self).__name__} requires keys {self.required_keys}, "
+                f"but storage at {self._load_path} only has {sorted(actual_keys)}. "
+                f"Missing: {missing}"
+            )
+
     def load(self, load_path: str, storage_type: Optional[str] = None, tokenizer=None):
         """Load dataset from the given path.
 
@@ -39,11 +59,16 @@ class BaseDataset(Dataset, ABC):
                           or None for auto-detection
             tokenizer: Callable str -> List[int], used to tokenize raw text
                        in JSON files. Ignored for HDF5.
+
+        Raises:
+            KeyError: If the loaded storage is missing required keys.
         """
         if storage_type is None:
             storage_type = detect_format(load_path)
         self.storage = StorageFactory.create(storage_type)
+        self._load_path = load_path
         self.storage.load(load_path, tokenizer=tokenizer)
+        self._validate_keys()
 
     def load_json(self, load_path: str, tokenizer=None):
         """Load dataset from JSON files explicitly.
@@ -186,6 +211,10 @@ class SEQDataset(BaseDataset):
     def __init__(self, window_size: int, stride: int):
         super().__init__(window_size, stride)
 
+    @property
+    def required_keys(self) -> List[str]:
+        return ["sequence"]
+
     def _fetch_data(self, begin_idx: int, end_idx: int) -> Tensor:
         return self.storage.fetch(begin_idx, end_idx, "sequence")
 
@@ -205,6 +234,10 @@ class SFTDataset(BaseDataset):
     def __init__(self, window_size: int, stride: int):
         super().__init__(window_size, stride)
 
+    @property
+    def required_keys(self) -> List[str]:
+        return ["sequence", "loss_mask"]
+
     def _fetch_data(self, begin_idx: int, end_idx: int, key: str) -> Tensor:
         return self.storage.fetch(begin_idx, end_idx, key)
 
@@ -229,6 +262,10 @@ class DPODataset(BaseDataset):
     def __init__(self, window_size: int, stride: int):
         super().__init__(window_size, stride)
 
+    @property
+    def required_keys(self) -> List[str]:
+        return ["chosen", "rejected", "chosen_mask", "rejected_mask"]
+
     def _fetch_data(self, begin_idx: int, end_idx: int, key: str) -> Tensor:
         return self.storage.fetch(begin_idx, end_idx, key)
 
@@ -259,6 +296,10 @@ class GRPODataset(BaseDataset):
     def __init__(self, window_size: int, stride: int):
         super().__init__(window_size, stride)
 
+    @property
+    def required_keys(self) -> List[str]:
+        return ["prompts", "responses", "masks", "rewards"]
+
     def _fetch_data(self, begin_idx: int, end_idx: int, key: str) -> Tensor:
         return self.storage.fetch(begin_idx, end_idx, key)