Fix: ensure .current file exists before usage (#40)

littlepay/config.py

@@ -21,14 +21,26 @@
 CONFIG_TYPES = list(DEFAULT_ACTIVE.keys())
 
 
+def _ensure_current_exists() -> bool:
+    """
+    Creates the CONFIG_FILE_CURRENT file if it doesn't already exist.
+
+    Returns (bool):
+        A flag indicating if the file existed or not.
+    """
+    exists = CONFIG_FILE_CURRENT.exists()
+    if not exists:
+        CONFIG_FILE_CURRENT.parent.mkdir(parents=True, exist_ok=True)
+        CONFIG_FILE_CURRENT.touch()
+    return exists
+
+
 def _get_current_path() -> Path:
     """
     Returns (Path):
         The path to the config file currently in-use, or the default.
     """
-    CONFIG_FILE_CURRENT.parent.mkdir(parents=True, exist_ok=True)
-    if not CONFIG_FILE_CURRENT.exists():
-        CONFIG_FILE_CURRENT.touch()
+    if not _ensure_current_exists():
         _update_current_path(DEFAULT_CONFIG_FILE)
     current = CONFIG_FILE_CURRENT.read_text().strip()
     return Path(current)
@@ -38,6 +50,7 @@ def _update_current_path(new_path: str | Path):
     """Saves new_path as the path to the current config file."""
     if isinstance(new_path, Path):
         new_path = str(new_path.expanduser().absolute())
+    _ensure_current_exists()
     CONFIG_FILE_CURRENT.write_text(new_path)
 
 

tests/test_config.py

@@ -6,6 +6,7 @@
 from littlepay.config import (
     DEFAULT_CONFIG,
     DEFAULT_CREDENTIALS,
+    _ensure_current_exists,
     _get_current_path,
     _read_config,
     _write_config,
@@ -15,45 +16,69 @@
 from tests.conftest import CUSTOM_CONFIG_FILE
 
 
-def test_get_current_path_default(custom_config_file: Path):
+@pytest.fixture
+def spy_ensure_current_exists(mocker):
+    return mocker.spy(littlepay.config, "_ensure_current_exists")
+
+
+def test_ensure_current_exists():
+    # reminder: the module-level variable littlepay.config.CONFIG_FILE_CURRENT
+    # is overwritten by the autouse fixture custom_current_file
+
+    # the .current file should not exist to begin with
+    assert not littlepay.config.CONFIG_FILE_CURRENT.exists()
+    assert _ensure_current_exists() is False
+
+    # now having ensured, the current file should exist
+    assert littlepay.config.CONFIG_FILE_CURRENT.exists()
+    # subsequent calls to ensure should indicate that it already exists
+    assert _ensure_current_exists()
+
+
+def test_get_current_path_default(custom_config_file: Path, spy_ensure_current_exists):
     result = _get_current_path()
 
     assert isinstance(result, Path)
     assert result.absolute() == custom_config_file.absolute()
+    assert spy_ensure_current_exists.call_count > 0
 
 
-def test_get_current_path_custom(custom_current_file: Path):
+def test_get_current_path_custom(custom_current_file: Path, spy_ensure_current_exists):
     expected = "."
     custom_current_file.write_text(expected)
 
     result = _get_current_path()
 
     assert result == Path(expected)
+    assert spy_ensure_current_exists.call_count > 0
 
 
-def test_get_current_path_newline(custom_current_file: Path):
+def test_get_current_path_newline(custom_current_file: Path, spy_ensure_current_exists):
     expected = "."
     custom_current_file.write_text(".\n")
 
     result = _get_current_path()
 
     assert result == Path(expected)
+    assert spy_ensure_current_exists.call_count > 0
 
 
-def test_update_current_path_str(custom_current_file: Path):
+def test_update_current_path_str(custom_current_file: Path, spy_ensure_current_exists):
     assert not custom_current_file.exists()
 
     _update_current_path("/the/path")
 
     assert custom_current_file.read_text() == "/the/path"
+    assert spy_ensure_current_exists.call_count > 0
 
 
-def test_update_current_path_Path(custom_current_file: Path):
+def test_update_current_path_Path(custom_current_file: Path, spy_ensure_current_exists):
     assert not custom_current_file.exists()
 
     _update_current_path(Path("/the/path"))
 
     assert custom_current_file.read_text() == "/the/path"
+    assert spy_ensure_current_exists.call_count > 0
 
 
 def test_read_config(custom_config_file: Path):