fix: create recursive_from_prefix path if it does not exist (#940)

# Reason
- #887 

# Changes
- create the recursive_from_prefix directory if it does not exist.
- add docstring to `get_destination_path`
- add unit tests for `get_destination_path`

client/python/cryoet_data_portal/src/cryoet_data_portal/_file_tools.py

@@ -57,21 +57,36 @@ def get_destination_path(
     dest_path: Optional[str],
     recursive_from_prefix: Optional[str] = None,
 ) -> str:
+    """
+    Get the destination path for a file download.
+
+    Args:
+        url (str): The URL to download
+        dest_path (str): The destination path the files will download to
+        recursive_from_prefix (str): All files under this prefix in the url will be downloaded to a path dest_path.
+        E.g. if the URL is https://example.com/a/b/file.txt, and the recursive_from_prefix would be
+        https://example.com/, then the dest_path would be dest_path/a/b/file.txt.
+
+    Returns:
+        str: The destination path for the file download
+
+    """
     if not dest_path:
         dest_path = os.getcwd()
     dest_path = os.path.abspath(dest_path)
 
-    if not os.path.isdir(dest_path) and recursive_from_prefix:
-        raise ValueError("Recursive downloads require a base directory")
-
     # If we're downloading recursively, we need to add the dest URL
     # (minus the prefix) to the dest path.
     if not recursive_from_prefix:
         recursive_from_prefix = url[0 : -len(os.path.basename(url))]
     path_suffix = url[len(recursive_from_prefix) :]
     dest_path = os.path.join(dest_path, os.path.dirname(path_suffix))
     if not os.path.isdir(dest_path):
-        os.makedirs(dest_path, exist_ok=True)
+        try:
+            os.makedirs(dest_path, exist_ok=True)
+        except Exception as e:
+            raise ValueError(f"Unable to create the path {dest_path}") from e
+
     dest_path = os.path.join(dest_path, os.path.basename(path_suffix))
     return dest_path
 

client/python/cryoet_data_portal/tests/test_file_tools.py

@@ -0,0 +1,64 @@
+import os
+from unittest.mock import patch
+
+import pytest
+
+from cryoet_data_portal._file_tools import get_destination_path
+
+
+class TestGetDestinationPath:
+    def test_url(self, tmp_path) -> None:
+        with patch("cryoet_data_portal._file_tools.os.getcwd", return_value=tmp_path):
+            url = "https://example.com/file.txt"
+            expected = os.path.join(tmp_path, "file.txt")
+            assert get_destination_path(url, None) == expected
+
+    def test_dest_path_exists(self, tmp_path) -> None:
+        url = "https://example.com/file.txt"
+        dest_path = os.path.join(tmp_path, "my_dest")
+        os.makedirs(dest_path)
+        expected = os.path.join(dest_path, "file.txt")
+        assert get_destination_path(url, dest_path) == expected
+
+    def test_dest_path_does_not_exist(self, tmp_path) -> None:
+        """Test that the destination path is created if it does not exist"""
+        url = "https://example.com/file.txt"
+        dest_path = os.path.join(tmp_path, "my_dest")
+        expected = os.path.join(dest_path, "file.txt")
+        assert get_destination_path(url, dest_path) == expected
+        assert os.path.isdir(dest_path)
+
+    def test_recursive_from_prefix_where_dest_path_exist(self, tmp_path) -> None:
+        """Test when a recursive_from_prefix is provided and the dest_path exists"""
+        url = "https://example.com/a/file.txt"
+        dest_path = os.path.join(tmp_path, "my_dest")
+        os.makedirs(dest_path)
+        recursive_from_prefix = "https://example.com/"
+        expected = os.path.join(dest_path, "a", "file.txt")
+        assert get_destination_path(url, dest_path, recursive_from_prefix) == expected
+
+    def test_recursive_from_prefix_where_dest_path_does_not_exist(
+        self,
+        tmp_path,
+    ) -> None:
+        """Test when a recursive_from_prefix is provided and the dest_path does not exist. The dest_path should be created."""
+        url = "https://example.com/a/b/file.txt"
+        dest_path = os.path.join(tmp_path, "my_dest")
+        recursive_from_prefix = "https://example.com/"
+        expected_path = os.path.join(dest_path, "a", "b")
+        expected = os.path.join(dest_path, "a", "b", "file.txt")
+        assert get_destination_path(url, dest_path, recursive_from_prefix) == expected
+        assert os.path.isdir(expected_path)
+
+    def test_invalid_dest_path(
+        self,
+        tmp_path,
+    ) -> None:
+        url = "https://example.com/file.txt"
+        dest_path = os.path.join(tmp_path, "\000")
+        recursive_from_prefix = "https://example.com/"
+        expected = os.path.join(dest_path, "file.txt")
+        with pytest.raises(ValueError):
+            assert (
+                get_destination_path(url, dest_path, recursive_from_prefix) == expected
+            )