* avoid missing image_key error for text-only datasets

+ support to expert to json format (not jsonl!)

data_juicer/core/exporter.py

@@ -176,7 +176,7 @@ def export(self, dataset):
     @staticmethod
     def to_jsonl(dataset, export_path, num_proc=1, **kwargs):
         """
-        Export method for json/jsonl target files.
+        Export method for jsonl target files.
 
         :param dataset: the dataset to export.
         :param export_path: the path to store the exported dataset.
@@ -186,6 +186,19 @@ def to_jsonl(dataset, export_path, num_proc=1, **kwargs):
         """
         dataset.to_json(export_path, force_ascii=False, num_proc=num_proc)
 
+    @staticmethod
+    def to_json(dataset, export_path, num_proc=1, **kwargs):
+        """
+        Export method for json target files.
+
+        :param dataset: the dataset to export.
+        :param export_path: the path to store the exported dataset.
+        :param num_proc: the number of processes used to export the dataset.
+        :param kwargs: extra arguments.
+        :return:
+        """
+        dataset.to_json(export_path, force_ascii=False, num_proc=num_proc, lines=False)
+
     @staticmethod
     def to_parquet(dataset, export_path, **kwargs):
         """
@@ -208,6 +221,6 @@ def _router():
         """
         return {
             'jsonl': Exporter.to_jsonl,
-            'json': Exporter.to_jsonl,
+            'json': Exporter.to_json,
             'parquet': Exporter.to_parquet,
         }

data_juicer/format/formatter.py

@@ -221,6 +221,8 @@ def non_empty_text(sample, target_keys):
         # function to convert relative paths to absolute paths
         def rel2abs(sample, path_keys, dataset_dir):
             for path_key in path_keys:
+                if path_key not in sample:
+                    continue
                 paths = sample[path_key]
                 if not paths:
                     continue