Function check_deterministic_pickle

tests/testutils.py:219–249

Check that two pickle output are bitwise equal. If it is not the case, print the diff between the disassembled pickle payloads. This helper is useful to investigate non-deterministic pickling.

(a, b)

def check_deterministic_pickle(a, b):
    """Check that two pickle output are bitwise equal.

    If it is not the case, print the diff between the disassembled pickle
    payloads.

    This helper is useful to investigate non-deterministic pickling.
    """
    if a != b:
        with io.StringIO() as out:
            pickletools.dis(pickletools.optimize(a), out)
            a_out = out.getvalue()
            # Remove the 11 first characters of each line to remove the bytecode offset
            # of each object, which is different on each line for very small differences,
            # making the diff very hard to read.
            a_out = "\n".join(ll[11:] for ll in a_out.splitlines())
        with io.StringIO() as out:
            pickletools.dis(pickletools.optimize(b), out)
            b_out = out.getvalue()
            b_out = "\n".join(ll[11:] for ll in b_out.splitlines())
        assert a_out == b_out
        full_diff = difflib.context_diff(
            a_out.splitlines(keepends=True), b_out.splitlines(keepends=True)
        )
        full_diff = "".join(full_diff)
        if len(full_diff) > 1500:
            full_diff = full_diff[:1494] + " [...]"
        raise AssertionError(
           "Pickle payloads are not bitwise equal:\n"
           + full_diff
        )


if __name__ == "__main__":