Add correct processing for non-existent json-keys

[klkvr]

Motivation

Right now following code will return uint256(32): abi.decode(vm.parseJson('{"a": 1}', '.b'), (uint256)) while expected behavior would be for it to revert because vm.parseJson('{"a": 1}', '.b') should result in bytes("")

But, in fact, it results in 0x00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000 == abi.encode(bytes(""))

Solution

Add processing of edge case when there are no json tokens corresponding to given path

[Evalir]

this lgtm—just unsure if this conforms to the earlier spec we had — @mds1 would love an eye on this!

[mds1]

Sanity checking my understanding: previously calling parseJson with a non-existent key returned bytes of abi.encode(bytes("")), and now it returns empty bytes, ""? If so, agreed with this change

Also @klkvr you might know this, but there's a keyExists cheat you can use to check if a key exists

[klkvr]

Sanity checking my understanding: previously calling parseJson with a non-existent key returned bytes of abi.encode(bytes("")), and now it returns empty bytes, ""? If so, agreed with this change

Yes, that's right

Also @klkvr you might know this, but there's a keyExists cheat you can use to check if a key exists

I know about it, but for me it's easier when code just reverts, because inserting sanity-checks everywhere makes code less readable IMO

[Evalir]

This is technically a breaking change @mds1 — should we merge or hold off?

[mds1]

I'd say merge (and include in the changelog) because the existing behavior feels like a footgun. We don't want to return data for a field that doesn't exist, since there really is no data.

Potentially related to #3754 (comment) where 32 used to be erroneously returned

[klkvr]

@Evalir parseJson does not revert if passed key does not exist, it just returns bytes which are not decodable to anything instead of abi.encode(bytes(""))

[Evalir]

whoops my bad, mixed another unrelated change here