must_write_to_tmp_path.py

"""
Depends on this in conftest.py

```python
import os
import pytest

@pytest.fixture(autouse=True)
def set_tmp_path_env(tmp_path):
    os.environ['PYTEST_TMP_PATH'] = str(tmp_path)
```
"""
import os
import sys
from pathlib import Path


def unit_tests_must_write_to_tmp_path(target_folder: Path)->None:
    """
    Checks if pytest is in the system modules and if the target folder is not within pytest's tmp_path.
    If the conditions are met, raise an exception to alert the developer.

    Args:
    target_folder (Path): The target folder to check as a Path object.
    """
    # Check if 'pytest' is among the loaded modules
    if "pytest" in sys.modules:
        if not target_folder:
            raise ValueError(f"Target file/folder {target_folder} must be set explicitly and inside tmp_path during unit testing.")
        # Attempt to get the tmp_path from an environment variable
        pytest_tmp_path_str = os.environ.get('PYTEST_TMP_PATH')

        if pytest_tmp_path_str is None:
            raise EnvironmentError("PYTEST_TMP_PATH environment variable is not set.")

        pytest_tmp_path = Path(pytest_tmp_path_str)

        # Check if the target folder is not within pytest's tmp_path
        if not pytest_tmp_path in target_folder.parents:
            raise ValueError(f"Target folder {target_folder} is outside pytest's tmp_path {pytest_tmp_path}.")

    # If not under pytest or if the check passes, do nothing
    return

if __name__ == '__main__':
    def example():
        # Example usage in your code
        # Assuming '/path/to/target/folder' is the path you want to check
        target_folder_path = '/path/to/target/folder'
        unit_tests_must_write_to_tmp_path(Path(target_folder_path))
    example()