ssh-encoding: add derive feature + extend derive functionallity #348
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Extend the derive macros to support all struct and enum types, not just
simple structs.
This also introduces some custom attributes to control the derived code.
Supported attributes:
- `#[ssh(length_prefixed)]`: will use length-prefix encoding/decoding
for the struct/enum as a whole, or per field, depending on where the
attribute is placed.
- `#[repr(u8)]`, `#[repr(u32)]` etc.: Enum discriminants will be
encoded/decoded depending on the specified repr used.
This is used in derived `Decode` implementations for enums. It holds a u128 because discriminants may be as large as u128/i128. Storing the value isn't strictly necessary, but allows a better error message.
Adds an optional feature that re-exports `ssh-derive` macros and exposes a documentation module with examples. The examples also serve as tests. Also adds tests for the derive feature in the form of declaring various structs and enums and asserting that encoding/decoding works as expected.
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tarcieri
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Mar 30, 2025
tarcieri
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Apr 19, 2025
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| /// Invalid discriminant value in message. | ||
| InvalidDiscriminant(u128), |
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It seems weird to me to conflate custom derive errors with this error type. Perhaps you could just define an error type in ssh-derive?
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Going to go ahead and merge this with one nit |
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I wanted to be able to derive
EncodeandDecodefor various message types in RFC 4253 and related RFCs. As the current implementation has some limitations (and I wanted to get some more macro-writing practice), I've gone ahead and extendedssh-derivequite a bit. The result is a rather substantial refactor, but it now supports all types of structs as well as enums. I realize this might be a bit much to review, but seeing asssh-deriveis0.0.1-alphaI figured it might be alright.This PR is really in two parts (let me know if it is better merged as two separate things):
ssh-derive:Encode/Decodeon all kinds of structs and enums.#[ssh(length_prefixed)]to use length prefixing when encoding/decoding. Can be applies to the struct/enum itself, or to individual fields.#[repr(u8)]and friends: Enum discriminants will encode/decode with the type specified by thereprattribute.ssh-encoding:derivefeature that re-exports the derive macros fromssh-derive.ssh_encoding::Errorto handle unexpected discriminant values when decoding.derivefeature.