Fallible storage get and set methods for Lazy and Mapping

[xermicus]

Adds try_* methods for reading and writing Lazy and Mapping values to and from storage (for Mapping, the encoded size of the key is also accounted for).

Fallible writes are implemented by extending the Storable trait with encoded_size method (which provides a default implementation using the SCALE version method of encoded_size). There is also size_hint in SCALE but I think we want an exact number and not an estimate. This will encode the stored value twice (the first time it's thrown away; no allocation happening), however users can optimize it by overwriting the encoded_size method to return a constant instead if possible and required.

Fallible reads are implemented using the contains_storage_key API, which will tell the size. This implies two calls to the contracts pallet (one to get the size and one to read the value). This can be improved by adding a corresponding ReturnCode to the contracts pallet, which can then be used by the get_storage API method. But for now, the two subsequent calls are necessary.

[xgreenx]

Looks good and clean to me=)

[paritytech-cicd-pr]

🦑 📈 ink! Example Contracts ‒ Changes Report 📉 🦑

These are the results when building the integration-tests/* contracts from this branch with cargo-contract 4.0.0-alpha-e8c2cfc and comparing them to ink! master:

Contract	Upstream Size (kB)	PR Size (kB)	Diff (kB)	Diff (%)	Change
basic-contract-caller	2.967	2.967	0	0	➖
basic-contract-caller/other-contract	1.337	1.337	0	0	➖
call-builder-return-value	8.688	8.735	0.047	0.540976	📈
call-runtime	1.769	1.769	0	0	➖
conditional-compilation	1.209	1.209	0	0	➖
contract-storage	7.124	7.171	0.047	0.659742	📈
contract-terminate	1.092	1.092	0	0	➖
contract-transfer	1.444	1.444	0	0	➖
custom-allocator	7.428	7.428	0	0	➖
dns	7.249	7.249	0	0	➖
e2e-call-runtime	1.058	1.058	0	0	➖
e2e-runtime-only-backend	1.635	1.635	0	0	➖
erc1155	14.026	13.962	-0.064	-0.456295	📉
erc20	6.687	6.687	0	0	➖
erc721	9.64	9.64	0	0	➖
events	4.763	4.763	0	0	➖
flipper	1.393	1.393	0	0	➖
incrementer	1.221	1.221	0	0	➖
lang-err-integration-tests/call-builder-delegate	2.317	2.317	0	0	➖
lang-err-integration-tests/call-builder	4.847	4.847	0	0	➖
lang-err-integration-tests/constructors-return-value	1.773	1.773	0	0	➖
lang-err-integration-tests/contract-ref	4.328	4.328	0	0	➖
lang-err-integration-tests/integration-flipper	1.571	1.571	0	0	➖
mapping-integration-tests	3.203	7.685	4.482	139.931	📈
mother	9.508	9.508	0	0	➖
multi-contract-caller	5.924	5.924	0	0	➖
multi-contract-caller/accumulator	1.095	1.095	0	0	➖
multi-contract-caller/adder	1.669	1.669	0	0	➖
multi-contract-caller/subber	1.689	1.689	0	0	➖
multisig	21.471	21.471	0	0	➖
payment-channel	5.501	5.501	0	0	➖
sr25519-verification	0.865	0.865	0	0	➖
static-buffer	1.405	1.405	0	0	➖
trait-dyn-cross-contract-calls	2.466	2.466	0	0	➖
trait-dyn-cross-contract-calls/contracts/incrementer	1.305	1.305	0	0	➖
trait-erc20	7.063	7.063	0	0	➖
trait-flipper	1.209	1.209	0	0	➖
trait-incrementer	1.37	1.37	0	0	➖
upgradeable-contracts/delegator	2.908	2.908	0	0	➖
upgradeable-contracts/delegator/delegatee	1.369	1.369	0	0	➖
upgradeable-contracts/set-code-hash	1.464	1.464	0	0	➖
upgradeable-contracts/set-code-hash/updated-incrementer	1.443	1.443	0	0	➖
wildcard-selector	2.622	2.622	0	0	➖

Link to the run | Last update: Fri Oct 27 13:13:23 CEST 2023

[ascjones]

Looks good! I'd like to see the try_ methods exercised in the mapping-integration-tests e2e tests though.

[ascjones]

LGTM! (needs merge conflict fixing)