Fix TextLineDataset to raise exception

backend/api/tests/data/example.txt

@@ -1,3 +1,4 @@
 exampleA
 exampleB
+
 exampleC

backend/api/tests/test_tasks.py

@@ -107,7 +107,7 @@ class TestIngestClassificationData(TestIngestData):
         filename = 'example.txt'
         file_format = 'TextFile'
         dataset = [
-            ('exampleA\nexampleB\nexampleC\n', [])
+            ('exampleA\nexampleB\n\nexampleC\n', [])
         ]
         self.ingest_data(filename, file_format)
         self.assert_examples(dataset)

backend/api/views/upload/dataset.py

@@ -153,11 +153,18 @@ class TextLineDataset(Dataset):
 
     def load(self, filename: str) -> Iterator[Record]:
         encoding = self.detect_encoding(filename)
+        errors = []
         with open(filename, encoding=encoding) as f:
-            for line in f:
-                data = self.data_class.parse(filename=filename, text=line.rstrip())
-                record = Record(data=data)
-                yield record
+            for line_num, line in enumerate(f, start=1):
+                try:
+                    data = self.data_class.parse(filename=filename, text=line.rstrip())
+                    record = Record(data=data)
+                    yield record
+                except ValidationError:
+                    message = 'The empty text is not allowed.'
+                    errors.append(FileParseException(filename, line_num, message))
+        if errors:
+            raise FileParseExceptions(errors)
 
 
 class CsvDataset(Dataset):