lisa.utils.chain_cm

lisa.utils.chain_cm(*fs)

Chain the context managers returned by the given callables.

This is equivalent to:

@contextlib.contextmanager
def combined(fs):
    fs = list(reversed(fs))

    with fs[0](x) as y:
        with fs[1](y) as z:
            with fs[2](z) as ...:
                ...
                with ... as final:
                    yield final

It is typically used instead of regular function composition when the functions return a context manager

@contextlib.contextmanager
def f(a, b):
    print(f'f a={a} b={b}')
    yield a + 10

@contextlib.contextmanager
def g(x):
    print(f'g x={x}')
    yield f'final x={x}'

combined = chain_cm(g, f)
with combined(a=1, b=2) as res:
    print(res)

# Would print:
#  f a=1 b=2
#  g x=11
#  final x=11