Fix add_document behaviour with empty string

meilisearch/_httprequests.py

@@ -45,7 +45,7 @@ def send_request(
                     request_path,
                     timeout=self.config.timeout,
                     headers=self.headers,
-                    data=json.dumps(body) if body else "null",
+                    data=json.dumps(body) if body else "" if body == "" else "null",
                 )
             return self.__validate(request)
 

tests/index/test_index_document_meilisearch.py

@@ -26,6 +26,16 @@ def test_add_documents(empty_index, small_movies):
     assert update.status == "succeeded"
 
 
+def test_add_documents_empty(empty_index):
+    """Tests adding empty string as documents to a clean index."""
+    index = empty_index()
+    with pytest.raises(Exception) as e_info:
+        index.add_documents("")
+    assert e_info.value.code == "missing_payload"
+    assert e_info.value.type == "invalid_request"
+    assert e_info.value.link == "https://docs.meilisearch.com/errors#missing_payload"
+
+
 @pytest.mark.parametrize("batch_size", [2, 3, 1000])
 @pytest.mark.parametrize(
     "primary_key, expected_primary_key",