bitfield_bytes(bits) should return chunks

[booleanfunction]

The simple-serialise (Merkleisation section) reads:

bitfield_bytes(bits): return the bits of the bitlist or bitvector, packed in bytes, aligned to the start. Length-delimiting bit for bitlists is excluded.

However when this function is called for merkleisation of bitvectors or bitlists, the output expected from bitfield_bytes is BYTES_PER_CHUNK-byte chunks, as indicated by the specification of merkleize, generally,

merkleize(chunks, limit=None)

and then the specific definition for bitvectors or bitlists:

merkleize(bitfield_bytes(value), limit=chunk_count(type)) if value is a bitvector.
mix_in_length(merkleize(bitfield_bytes(value), limit=chunk_count(type)), len(value)) if value is a bitlist.

[hwwhww]

Thanks for the report!

I suppose the spec is misleading but the implementations are correct? (py-ssz is correct)
/cc @protolambda for checking remerkleable

Ideally, maybe rename bitfield_bytes to pack_bits would be more clear.

pack(value): given ordered objects of the same basic type, serialize them, pack them into BYTES_PER_CHUNK-byte chunks, right-pad the last chunk with zero bytes, and return the chunks.
pack_bits(bits): Given the bits of bitlist or bitvector, get bitfield_bytes by packing them in bytes and aligning to the start. Length-delimiting bit for bitlists is excluded. And them pack bitfield_bytes into BYTES_PER_CHUNK-byte chunks, right-pad the last chunk with zero bytes, and return the chunks.

merkleize(pack_bits(value), limit=chunk_count(type)) if value is a bitvector.
mix_in_length(merkleize(pack_bits(value), limit=chunk_count(type)), len(value)) if value is a bitlist.

[protolambda]

Closing this, I think this is solved in #1806