paritytech/scale-type-resolver

A low level trait to be generic over how to resolve SCALE type information

scale-type-resolver

scale-type-resolver provides a generic TypeResolver trait which can be implemented for any type that is capable of being given a type ID and resolving that into information about how the type is SCALE encoded. This allows libraries like scale-decode to be able to decode SCALE encoded bytes using either a modern type resolver like scale_info::PortableRegistry, or using entirely custom type resolvers (which we would need in order decode blocks from pre-V14 metadata).

It's unlikely that you'd depend on this library directly; more likely you'd depend on a library like scale-decode which uses and re-exports the TypeResolver trait itself.

This crate is no_std by default and doesn't require alloc except for tests.

scale-type-resolver's Issues

Consider exposing optional name/path of variant/composite types

In scale_info::PortableRegistry we can obtain the path of composite and variant types. This isn't relevant for normal encoding and decoding, but may be useful in a couple of other scenarios:

• If I make a custom type with custom encoding/decoding in order to mirror some Substrate type, I may want to be able to check in the EncodeAsType/DecodeAsType impls that the target type has the expected name (ie is likely to have led to the same custom encoding/decoding).
• I may want to be able to return the target type name/path in errors.

This information is not mandatory and so I think it should be optional whether a TypeResolver implementation provides it or not (ie for V14 types, we can always provide it, but for older types it may be easier if the user doesn't have to provide such information.