perseus-macro 0.4.2

#![doc = include_str!("../README.proj.md")]
/*!
## Features

- `live-reload` -- enables reloading the browser automatically when you make changes to your app
- `hsr` -- enables *hot state reloading*, which reloads the state of your app right before you made code changes in development, allowing you to pick up where you left off

## Packages

This is the API documentation for the `perseus-macro` package, which manages Perseus' procedural macros. Note that Perseus mostly uses [the book](https://framesurge.sh/perseus/en-US) for
documentation, and this should mostly be used as a secondary reference source. You can also find full usage examples [here](https://github.com/framesurge/perseus/tree/main/examples).
*/

mod auto_scope;
mod entrypoint;
mod rx_state;
mod test;

use darling::{FromDeriveInput, FromMeta};
use proc_macro::TokenStream;
use quote::quote;
use syn::{parse_macro_input, DeriveInput, ItemFn, Path, Signature};

use crate::rx_state::ReactiveStateDeriveInput;

/// A helper macro for templates that use reactive state. Once, this was needed
/// on all Perseus templates, however, today, templates that take no state, or
/// templates that take unreactive state, can be provided as normal functions
/// to the methods `.view()` and `.view_with_unreactive_state()`
/// respectively, on Perseus' `Template` type.
///
/// In fact, even if you're using fully reactive state, this macro isn't even
/// mandated anymore! It just exists to turn function signatures like this
///
/// ```text
/// fn my_page<'a, G: Html>(cx: BoundedScope<'_, 'a>, state: &'a MyStateRx) -> View<G>
/// ```
///
/// into this
///
/// ```text
/// #[auto_scope]
/// fn my_page<G: Html>(cx: Scope, state: &MyStateRx) -> View<G>
/// ```
///
/// In other words, all this does is rewrites some lifetimes for you so Perseus
/// is a little more convenient to use! It's worth remembering, however, when
/// you use this macro, that the `Scope` is actually a `BoundedScope<'app,
/// 'page>`, meaning it is a *child scope* of the whole app. Your state is a
/// reference with the lifetime `'page`, which links to an owned type that the
/// app controls. All this lifetime complexity is needed to make sure Rust
/// understands that all your pages are part of your app, and that, when one of
/// your users goes to a new page, the previous page will be dropped, along with
/// all its artifacts (e.g. any `create_effect` calls). It also makes it really
/// convenient to use your state, because we can prove to Sycamore that it will
/// live long enough to be interpolated anywhere in your page's `view!`.
///
/// If you dislike macros, or if you want to make the lifetimes of a page very
/// clear, it's recommended that you don't use this macro, and manually write
/// the longer function signatures instead. However, if you like the convenience
/// of it, this macro is here to help!
///
/// *Note: this can also be used for capsules that take reactive state, it's not
/// just limited to templates.*
#[proc_macro_attribute]
pub fn auto_scope(_args: TokenStream, input: TokenStream) -> TokenStream {
    let parsed = syn::parse_macro_input!(input as auto_scope::TemplateFn);
    auto_scope::template_impl(parsed).into()
}

/// Marks the given function as a Perseus test. Functions marked with this
/// attribute must have the following signature: `async fn foo(client: &mut
/// fantoccini::Client) -> Result<>`.
#[proc_macro_attribute]
pub fn test(args: TokenStream, input: TokenStream) -> TokenStream {
    let parsed = syn::parse_macro_input!(input as test::TestFn);
    let attr_args = syn::parse_macro_input!(args as syn::AttributeArgs);
    // Parse macro arguments with `darling`
    let args = match test::TestArgs::from_list(&attr_args) {
        Ok(v) => v,
        Err(e) => {
            return TokenStream::from(e.write_errors());
        }
    };

    test::test_impl(parsed, args).into()
}

/// Marks the given function as the universal entrypoint into your app. This is
/// designed for simple use-cases, and the annotated function should return
/// a `PerseusApp`. This will expand into separate `main()` functions for both
/// the browser and engine sides.
///
/// This should take an argument for the function that will produce your server.
/// In most apps using this macro (which is designed for simple use-cases), this
/// will just be something like `perseus_axum::dflt_server` (with `perseus-warp`
/// as a dependency with the `dflt-server` feature enabled).
///
/// Note that the `dflt-engine` and `client-helpers` features must be enabled on
/// `perseus` for this to work. (These are enabled by default.)
///
/// Note further that you'll need to have `wasm-bindgen` as a dependency to use
/// this.
#[proc_macro_attribute]
pub fn main(args: TokenStream, input: TokenStream) -> TokenStream {
    let parsed = syn::parse_macro_input!(input as entrypoint::MainFn);
    let args = syn::parse_macro_input!(args as Path);

    entrypoint::main_impl(parsed, args).into()
}

/// This is identical to `#[main]`, except it doesn't require a server
/// integration, because it sets your app up for exporting only. This is useful
/// for apps not using server-requiring features (like incremental static
/// generation and revalidation) that want to avoid bringing in another
/// dependency on the server-side.
#[proc_macro_attribute]
pub fn main_export(_args: TokenStream, input: TokenStream) -> TokenStream {
    let parsed = syn::parse_macro_input!(input as entrypoint::MainFn);

    entrypoint::main_export_impl(parsed).into()
}

/// Marks the given function as the browser entrypoint into your app. This is
/// designed for more complex apps that need to manually distinguish between the
/// engine and browser entrypoints.
///
/// If you just want to run some simple customizations, you should probably use
/// `perseus::run_client` to use the default client logic after you've made your
/// modifications. `perseus::ClientReturn` should be your return type no matter
/// what.
///
/// Note that any generics on the annotated function will not be preserved. You
/// should put the `PerseusApp` generator in a separate function.
///
/// Note further that you'll need to have `wasm-bindgen` as a dependency to use
/// this.
#[proc_macro_attribute]
pub fn browser_main(_args: TokenStream, input: TokenStream) -> TokenStream {
    let parsed = syn::parse_macro_input!(input as entrypoint::MainFn);

    entrypoint::browser_main_impl(parsed).into()
}

/// Marks the given function as the engine entrypoint into your app. This is
/// designed for more complex apps that need to manually distinguish between the
/// engine and browser entrypoints.
///
/// If you just want to run some simple customizations, you should probably use
/// `perseus::run_dflt_engine` with `perseus::builder::get_op` to use the
/// default client logic after you've made your modifications. You'll also want
/// to return an exit code from this function (use `std::process:exit(..)`).
///
/// Note that the `dflt-engine` and `client-helpers` features must be enabled on
/// `perseus` for this to work. (These are enabled by default.)
///
/// Note further that you'll need to have `tokio` as a dependency to use this.
///
/// Finally, note that any generics on the annotated function will not be
/// preserved. You should put the `PerseusApp` generator in a separate function.
#[proc_macro_attribute]
pub fn engine_main(_args: TokenStream, input: TokenStream) -> TokenStream {
    let parsed = syn::parse_macro_input!(input as entrypoint::EngineMainFn);

    entrypoint::engine_main_impl(parsed).into()
}

/// Processes the given `struct` to create a reactive version by wrapping each
/// field in a `Signal`. This will generate a new `struct` with the given name
/// and implement a `.make_rx()` method on the original that allows turning an
/// instance of the unreactive `struct` into an instance of the reactive one.
///
/// If one of your fields is itself a `struct`, by default it will just be
/// wrapped in a `Signal`, but you can also enable nested fine-grained
/// reactivity by adding the `#[rx(nested)]` helper macro to the field.
/// Fields that have nested reactivity should also use this derive macro.
#[proc_macro_derive(ReactiveState, attributes(rx))]
pub fn reactive_state(input: TokenStream) -> TokenStream {
    let input = match ReactiveStateDeriveInput::from_derive_input(&syn::parse_macro_input!(
        input as DeriveInput
    )) {
        Ok(input) => input,
        Err(err) => return err.write_errors().into(),
    };

    rx_state::make_rx_impl(input).into()
}

/// A convenience macro that makes sure the given function is only defined on
/// the engine-side, creating an empty function on the browser-side. Perseus
/// implicitly expects most of your state generation functions to be defined in
/// this way (though you certainly don't have to use this macro).
///
/// Note that this will convert `async` functions to non-`async` functions on
/// the browser-side (your function will be left alone on the engine-side).
#[proc_macro_attribute]
pub fn engine_only_fn(_args: TokenStream, input: TokenStream) -> TokenStream {
    let input_2: proc_macro2::TokenStream = input.clone().into();
    let ItemFn {
        vis,
        sig: Signature { ident, .. },
        ..
    } = parse_macro_input!(input as ItemFn);

    quote! {
        #[cfg(client)]
        #vis fn #ident () {}
        // On the engine-side, the function is unmodified
        #[cfg(engine)]
        #input_2
    }
    .into()
}

/// A convenience macro that makes sure the given function is only defined on
/// the browser-side, creating an empty function on the engine-side. Perseus
/// implicitly expects your browser-side state modification functions to be
/// defined in this way (though you certainly don't have to use this macro).
///
/// Note that this will convert `async` functions to non-`async` functions on
/// the engine-side (your function will be left alone on the browser-side).
#[proc_macro_attribute]
pub fn browser_only_fn(_args: TokenStream, input: TokenStream) -> TokenStream {
    let input_2: proc_macro2::TokenStream = input.clone().into();
    let ItemFn {
        vis,
        sig: Signature { ident, .. },
        ..
    } = parse_macro_input!(input as ItemFn);

    quote! {
        #[cfg(engine)]
        #vis fn #ident () {}
        // One the browser-side, the function is unmodified
        #[cfg(client)]
        #input_2
    }
    .into()
}

#[proc_macro_derive(UnreactiveState)]
pub fn unreactive_state(input: TokenStream) -> TokenStream {
    let input = syn::parse_macro_input!(input as DeriveInput);
    let name = input.ident;

    // This is a marker trait, so we barely have to do anything here
    quote! {
        impl ::perseus::state::UnreactiveState for #name {}
    }
    .into()
}