enhancement(derives): extend enum macro to accept any ident and refactor enums

[borngraced]

#1595
Previously, the EnumFromStringy macro was exclusively utilized to produce the From trait from one enum to another enum only when the inner identifier was "String". However, to enhance this utility, I've expanded the macro's functionality to allow any identifier.

This will eliminates the need for code repetition such as the following while decreasing the codebase to some extent :) :

impl From<rlp::DecoderError> for ValidatePaymentError {
    fn from(err: rlp::DecoderError) -> Self { Self::TxDeserializationError(err.to_string()) }
}

impl From<web3::Error> for ValidatePaymentError {
    fn from(err: web3::Error) -> Self { Self::Transport(err.to_string()) }
}

impl From<NumConversError> for ValidatePaymentError {
    fn from(err: NumConversError) -> Self { Self::InternalError(err.to_string()) }
}

impl From<SPVError> for ValidatePaymentError {
    fn from(err: SPVError) -> Self { Self::SPVError(err) }
}

impl From<serialization::Error> for ValidatePaymentError {
    fn from(err: serialization::Error) -> Self { Self::TxDeserializationError(err.to_string()) }
}

impl From<UnexpectedDerivationMethod> for ValidatePaymentError {
    fn from(err: UnexpectedDerivationMethod) -> Self { Self::InternalError(err.to_string()) }
}


And just do this instead 


pub enum ValidatePaymentError {
    /// Should be used to indicate internal MM2 state problems (e.g., DB errors, etc.).
    #[from_stringify("NumConversError", "UnexpectedDerivationMethod", "keys::Error")]
    InternalError(String),
    /// Problem with deserializing the transaction, or one of the transaction parts is invalid.
    #[from_stringify("rlp::DecoderError", "serialization::Error")]
    TxDeserializationError(String),
    /// SPV client error.
    #[from_stringify("SPVError")]
    SPVError(SPVError),
    …
}


So it doesn’t matter if a field inner ident is string or not

[dimxy]

btw there is a similar feature https://docs.rs/thiserror/latest/thiserror/. An interesting feature in it is formatting error message with interpolating nested error

[borngraced]

btw there is a similar feature https://docs.rs/thiserror/latest/thiserror/. An interesting feature in it is formatting error message with interpolating nested error

seems cool really, but it still depends on anyhow error crate. we might want to keep this and keep extending I guess

[shamardy]

@borngraced please resolve conflicts in this PR.

[dimxy]

I tried EnumFromStringify with the new option, like:

#[from_stringify("SPVError")]
    SPVError(SPVError),

I think this may be preferable, because when printing the outer error in the debug format this option prints the nested error in debug as well. How about from_nested or just from?

Question: why the macro is called 'from_stringify' although there is no 'stringify' in the new option?
Also: maybe good to mention when #[from_stringify("SPVError")] SPVError(String), is used (with conversion to String) then nested SPVError must implement Display trait.

[dimxy]

BTW the function derive_enum_from_macro in the unsupported case of 'struct' or 'union' always returns ENUM_FROM_INNER_IDENT tag in the error, although derive_enum_from_macro fn could be also called for EnumFromStringify and EnumFromTrait

[dimxy]

Also I think you need to update the doc for EnumFromStringify:

• This note // E.G, this converts from Bar, Man to FooBar::Bar(String) does not fully match to the example code (#[from_stringify("u64", "std::io::Error")]).
• Please, add a sample for the new feature with non-String nested types.

There are identical doc comments /// Implements `From<Inner>` trait for the given enumeration both for EnumFromInner and EnumFromTrait macros. Should the second one be changed for EnumFromTrait?

[borngraced]

Also I think you need to update the doc for EnumFromStringify:

• This note // E.G, this converts from Bar, Man to FooBar::Bar(String) does not fully match to the example code (#[from_stringify("u64", "std::io::Error")]).
• Please, add a sample for the new feature with non-String nested types.

There are identical doc comments /// Implements `From<Inner>` trait for the given enumeration both for EnumFromInner and EnumFromTrait macros. Should the second one be changed for EnumFromTrait?

updated