byte array argument packing for method doesn't comply with ABI

[denis-bogdanas]

According to ABI specification dynamic part of byte arrays should be encoded like this:
enc(X) = enc(k) pad_right(X)

Right now they are properly encoded for events, but not for methods. For methods byte arrays are not padded to full chunks of 32 bytes, but are encoded like this:

enc(X) = enc(k) X

Curiously python ethereum API is compatible with this encoding, so this test passes:

def test_selfcall_code_zz(get_contract_with_gas_estimation):
    selfcall_code_6 = """
@public
def hardtest(arg1: bytes <= 64, arg2: bytes <= 64) -> bytes <= 128:
    return concat(arg1, arg2)
    """

    c = get_contract_with_gas_estimation(selfcall_code_6)
    assert c.hardtest(b"hello" * 5, b"hello" * 10) == b"hello" * 15

Looks like an issue in both ethereum API and Vyper, that will likely cause problems in production. Also harmonizing encoding format will allow using the same algorithm for both event and method args.

[jacqueswww]

Very strange that it actually works! +1 for using pad_right.
And +1 for refactoring the packing of arguments code.

[jacqueswww]

Closing, this works now 😄 I also added a test for it: #1158