Make JSON builder support an array of strings (#6696)

* Test JSON builder with list of strings

* Make JSON builder support array of strings

src/datasets/packaged_modules/json/json.py

@@ -145,12 +145,20 @@ def _generate_tables(self, files):
                             except json.JSONDecodeError:
                                 logger.error(f"Failed to read file '{file}' with error {type(e)}: {e}")
                                 raise e
-                            # If possible, parse the file as a list of json objects and exit the loop
+                            # If possible, parse the file as a list of json objects/strings and exit the loop
                             if isinstance(dataset, list):  # list is the only sequence type supported in JSON
                                 try:
-                                    keys = set().union(*[row.keys() for row in dataset])
-                                    mapping = {col: [row.get(col) for row in dataset] for col in keys}
-                                    pa_table = pa.Table.from_pydict(mapping)
+                                    if dataset and isinstance(dataset[0], str):
+                                        pa_table_names = (
+                                            list(self.config.features)
+                                            if self.config.features is not None
+                                            else ["text"]
+                                        )
+                                        pa_table = pa.Table.from_arrays([pa.array(dataset)], names=pa_table_names)
+                                    else:
+                                        keys = set().union(*[row.keys() for row in dataset])
+                                        mapping = {col: [row.get(col) for row in dataset] for col in keys}
+                                        pa_table = pa.Table.from_pydict(mapping)
                                 except (pa.ArrowInvalid, AttributeError) as e:
                                     logger.error(f"Failed to read file '{file}' with error {type(e)}: {e}")
                                     raise ValueError(f"Not able to read records in the JSON file at {file}.") from None

tests/packaged_modules/test_json.py

@@ -54,6 +54,23 @@ def json_file_with_list_of_dicts(tmp_path):
     return str(filename)
 
 
+@pytest.fixture
+def json_file_with_list_of_strings(tmp_path):
+    filename = tmp_path / "file_with_list_of_strings.json"
+    data = textwrap.dedent(
+        """\
+        [
+            "First text.",
+            "Second text.",
+            "Third text."
+        ]
+        """
+    )
+    with open(filename, "w") as f:
+        f.write(data)
+    return str(filename)
+
+
 @pytest.fixture
 def json_file_with_list_of_dicts_field(tmp_path):
     filename = tmp_path / "file_with_list_of_dicts_field.json"
@@ -82,13 +99,18 @@ def json_file_with_list_of_dicts_field(tmp_path):
         ("jsonl_file_utf16_encoded", {"encoding": "utf-16"}),
         ("json_file_with_list_of_dicts", {}),
         ("json_file_with_list_of_dicts_field", {"field": "field3"}),
+        ("json_file_with_list_of_strings", {}),
     ],
 )
 def test_json_generate_tables(file_fixture, config_kwargs, request):
     json = Json(**config_kwargs)
     generator = json._generate_tables([[request.getfixturevalue(file_fixture)]])
     pa_table = pa.concat_tables([table for _, table in generator])
-    assert pa_table.to_pydict() == {"col_1": [-1, 1, 10], "col_2": [None, 2, 20]}
+    if file_fixture == "json_file_with_list_of_strings":
+        expected = {"text": ["First text.", "Second text.", "Third text."]}
+    else:
+        expected = {"col_1": [-1, 1, 10], "col_2": [None, 2, 20]}
+    assert pa_table.to_pydict() == expected
 
 
 @pytest.mark.parametrize(