FA1.2 operations emitted by view entrypoints

Should the views emit exactly one operation (corresponding to the transfer) or at most one?

Furthermore, what should happen if the entrypoint receives a nonzero amount of tez? Should these be sent back? Is this entrypoint allowed to fail?

assigned to @gromak

View Entrypoints section provides implementation of VIEW macro:

VIEW :: view a r : storage : S -> (list operation, storage) : S
VIEW code =
  UNPAIR; DIP {DUUP}; PAIR; code; DIP {AMOUNT};
  TRANSFER_TOKENS; NIL operation; SWAP; CONS; PAIR;
  where
    code :: (a, storage) : S -> r : S

Each view entrypoint is supposed to behave equivalently to this definition (it's not stated explicitly though). That is, it must return exactly one TRANSFER_TOKENS operation targeting the contract passed as an argument. This transaction's amount must be equal to AMOUNT passed to the view entrypoint, i. e. all tez passed to a view entrypoint is forwarded to the callback contract.

One problem with views is that TZIP-4 is now deprecated while TZIP-7 is final and refers to TZIP-4. TZIP-5 (FA1) is deprecated as well, but TZIP-7 is based on TZIP-5. So I propose the following:

1. Undeprecate TZIP-5.
2. Update the description of "View entrypoints" (it's a bit outdated and imprecise and mentioned above), inline this new description into TZIP-5.

Sounds good Ivan, thanks.

mentioned in issue camlcase-dev/fa1.2#1 (closed)

added FA1.2 label

mentioned in commit 0cb7705f

mentioned in merge request !99 (merged)

mentioned in merge request !98 (merged)

closed

mentioned in commit b986ed24

mentioned in commit 3e0abe05

mentioned in commit 05cfb16a