A decorator for building a temporary directory with prepopulated files.

tempdir.py

from functools import wraps
try:
    # py>=3.2
    from tempfile import TemporaryDirectory
except ImportError:
    from backports.tempfile import TemporaryDirectory
from pathlib2 import Path

def tempdir(files=None, **kw):
    """
    A decorator for building a temporary directory with prepopulated files.

    The temproary directory and files are created just before the wrapped function is called and are destroyed
    imediately after the wrapped function returns.

    The `files` keyword should be a dict of file paths as keys and strings of file content as values.
    If `files` is a list, then each item is assumed to be a path of an empty file. All other
    keywords are passed to `tempfile.TemporaryDirectory` to create the parent directory.

    In the following example, two files are created in the temporary directory and then are destroyed when
    the function exits:

        @tempdir(files={
            'foo.txt': 'foo content',
            'bar.txt': 'bar content'
        })
        def example(dir):
            assert Path(dir, 'foo.txt').is_file()
            p = Path(dir, 'bar.txt')
            assert p.is_file()
            assert p.read_text(encoding='utf-8') == 'bar content'
    """
    files = {f: '' for f in files} if isinstance(files, (list, tuple)) else files or {}
    def decorator(fn):
        @wraps(fn)
        def wrapper(*args, **kwargs):
            with TemporaryDirectory(**kw) as td:
                for path, content in files.items():
                    Path(td, path).write_text(content, encoding='utf-8')
                return fn(td, *args, **kwargs)
        return wrapper
    return decorator