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# Description This PR allows the helper attribute `nu_value(rename = "...")` to be used on struct fields and enum variants. This allows renaming keys and variants just like [`#[serde(rename = "name")]`](https://serde.rs/field-attrs.html#rename). This has no singular variants for `IntoValue` or `FromValue`, both need to use the same (but I think this shouldn't be an issue for now). # User-Facing Changes Users of the derive macros `IntoValue` and `FromValue` may now use `#[nu_value(rename = "...")]` to rename single fields, but no already existing code will break.
72 lines
2.9 KiB
Rust
72 lines
2.9 KiB
Rust
//! Macro implementations of `#[derive(FromValue, IntoValue)]`.
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//!
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//! As this crate is a [`proc_macro`] crate, it is only allowed to export
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//! [procedural macros](https://doc.rust-lang.org/reference/procedural-macros.html).
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//! Therefore, it only exports [`IntoValue`] and [`FromValue`].
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//!
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//! To get documentation for other functions and types used in this crate, run
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//! `cargo doc -p nu-derive-value --document-private-items`.
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//!
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//! This crate uses a lot of
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//! [`proc_macro2::TokenStream`](https://docs.rs/proc-macro2/1.0.24/proc_macro2/struct.TokenStream.html)
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//! as `TokenStream2` to allow testing the behavior of the macros directly, including the output
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//! token stream or if the macro errors as expected.
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//! The tests for functionality can be found in `nu_protocol::value::test_derive`.
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//!
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//! This documentation is often less reference-heavy than typical Rust documentation.
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//! This is because this crate is a dependency for `nu_protocol`, and linking to it would create a
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//! cyclic dependency.
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//! Also all examples in the documentation aren't tested as this crate cannot be compiled as a
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//! normal library very easily.
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//! This might change in the future if cargo allows building a proc-macro crate differently for
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//! `cfg(doctest)` as they are already doing for `cfg(test)`.
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//!
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//! The generated code from the derive macros tries to be as
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//! [hygienic](https://doc.rust-lang.org/reference/macros-by-example.html#hygiene) as possible.
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//! This ensures that the macro can be called anywhere without requiring specific imports.
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//! This results in obtuse code, which isn't recommended for manual, handwritten Rust
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//! but ensures that no other code may influence this generated code or vice versa.
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use proc_macro::TokenStream;
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use proc_macro2::TokenStream as TokenStream2;
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use proc_macro_error::{proc_macro_error, Diagnostic};
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mod attributes;
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mod case;
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mod error;
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mod from;
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mod into;
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mod names;
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#[cfg(test)]
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mod tests;
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const HELPER_ATTRIBUTE: &str = "nu_value";
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/// Derive macro generating an impl of the trait `IntoValue`.
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///
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/// For further information, see the docs on the trait itself.
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#[proc_macro_derive(IntoValue, attributes(nu_value))]
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#[proc_macro_error]
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pub fn derive_into_value(input: TokenStream) -> TokenStream {
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let input = TokenStream2::from(input);
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let output = match into::derive_into_value(input) {
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Ok(output) => output,
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Err(e) => Diagnostic::from(e).abort(),
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};
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TokenStream::from(output)
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}
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/// Derive macro generating an impl of the trait `FromValue`.
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///
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/// For further information, see the docs on the trait itself.
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#[proc_macro_derive(FromValue, attributes(nu_value))]
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#[proc_macro_error]
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pub fn derive_from_value(input: TokenStream) -> TokenStream {
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let input = TokenStream2::from(input);
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let output = match from::derive_from_value(input) {
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Ok(output) => output,
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Err(e) => Diagnostic::from(e).abort(),
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};
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TokenStream::from(output)
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}
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