file-api: add checks for missin values/paths

Author: aldogonzalez8

airbyte_cdk/sources/declarative/retrievers/file_uploader.py

@@ -45,7 +45,11 @@ def __post_init__(self, parameters: Mapping[str, Any]) -> None:
     def upload(self, record: Record) -> None:
         mocked_response = SafeResponse()
         mocked_response.content = json.dumps(record.data).encode()
-        download_target = list(self.download_target_extractor.extract_records(mocked_response))[0]
+        download_targets = list(self.download_target_extractor.extract_records(mocked_response))
+        if not download_targets:
+            raise ValueError("No download targets found")
+
+        download_target = download_targets[0] # we just expect one download target
         if not isinstance(download_target, str):
             raise ValueError(
                 f"download_target is expected to be a str but was {type(download_target)}: {download_target}"

airbyte_cdk/sources/file_based/file_based_stream_reader.py

@@ -186,6 +186,9 @@ def _get_file_transfer_paths(
             - FILE_NAME: The name of the referenced file.
             - FILE_FOLDER: The folder of the referenced file.
         """
+        if not path.exists(staging_directory):
+            raise ValueError(f"Staging directory '{staging_directory}' does not exist")
+        
         preserve_directory_structure = self.preserve_directory_structure()
 
         file_name = path.basename(source_file_relative_path)