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// Copyright (C) 2022 Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! Generates the bounds for a particular subsystem `Context` and associate `type Sender`.
//!
//!
//! ## Implement `trait Subsystem<Context, Error>` via `subsystem`
//!
//! ```ignore
//! # use orchestra_proc_macro::subsystem;
//! # mod somewhere {
//! # use orchestra_proc_macro::orchestra;
//! # pub use orchestra::*;
//! #
//! # #[derive(Debug, thiserror::Error)]
//! # #[error("Yikes!")]
//! # pub struct Yikes;
//! # impl From<OrchestraError> for Yikes {
//! # fn from(_: OrchestraError) -> Yikes { Yikes }
//! # }
//! # impl From<mpsc::SendError> for Yikes {
//! # fn from(_: mpsc::SendError) -> Yikes { Yikes }
//! # }
//! #
//! # #[derive(Debug)]
//! # pub struct Eve;
//! #
//! # #[derive(Debug, Clone)]
//! # pub struct Sig;
//! #
//! # #[derive(Debug, Clone, Copy)]
//! # pub struct A;
//! # #[derive(Debug, Clone, Copy)]
//! # pub struct B;
//! #
//! # #[orchestra(signal=Sig, gen=AllOfThem, event=Eve, error=Yikes)]
//! # pub struct Wonderland {
//! # #[subsystem(A, sends: [B])]
//! # foo: Foo,
//! # #[subsystem(B, sends: [A])]
//! # bar: Bar,
//! # }
//! # }
//! # use somewhere::{Yikes, SpawnedSubsystem};
//! #
//! # struct FooSubsystem;
//! #
//! #[subsystem(Foo, error = Yikes, prefix = somewhere)]
//! impl<Context> FooSubsystem {
//! fn start(self, context: Context) -> SpawnedSubsystem<Yikes> {
//! // ..
//! # let _ = context;
//! # unimplemented!()
//! }
//! }
//! ```
//!
//! expands to
//!
//! ```ignore
//! # use orchestra_proc_macro::subsystem;
//! # mod somewhere {
//! # use orchestra_proc_macro::orchestra;
//! # pub use orchestra::*;
//! #
//! # #[derive(Debug, thiserror::Error)]
//! # #[error("Yikes!")]
//! # pub struct Yikes;
//! # impl From<OrchestraError> for Yikes {
//! # fn from(_: OrchestraError) -> Yikes { Yikes }
//! # }
//! # impl From<mpsc::SendError> for Yikes {
//! # fn from(_: mpsc::SendError) -> Yikes { Yikes }
//! # }
//! #
//! # #[derive(Debug)]
//! # pub struct Eve;
//! #
//! # #[derive(Debug, Clone)]
//! # pub struct Sig;
//! #
//! # #[derive(Debug, Clone, Copy)]
//! # pub struct A;
//! # #[derive(Debug, Clone, Copy)]
//! # pub struct B;
//! #
//! # #[orchestra(signal=Sig, gen=AllOfThem, event=Eve, error=Yikes)]
//! # pub struct Wonderland {
//! # #[subsystem(A, sends: [B])]
//! # foo: Foo,
//! # #[subsystem(B, sends: [A])]
//! # bar: Bar,
//! # }
//! # }
//! # use somewhere::{Yikes, SpawnedSubsystem};
//! # use orchestra as support_crate;
//! #
//! # struct FooSubsystem;
//! #
//! impl<Context> support_crate::Subsystem<Context, Yikes> for FooSubsystem
//! where
//! Context: somewhere::FooContextTrait,
//! Context: support_crate::SubsystemContext,
//! <Context as somewhere::FooContextTrait>::Sender: somewhere::FooSenderTrait,
//! <Context as support_crate::SubsystemContext>::Sender: somewhere::FooSenderTrait,
//! {
//! fn start(self, context: Context) -> SpawnedSubsystem<Yikes> {
//! // ..
//! # let _ = context;
//! # unimplemented!()
//! }
//! }
//! ```
//!
//! where `support_crate` is either equivalent to `somewhere` or derived from the cargo manifest.
//!
//!
//! ## Add additional trait bounds for a generic `Context` via `contextbounds`
//!
//! ### To an `ImplItem`
//!
//! ```ignore
//! #[contextbounds(Foo, prefix = somewhere)]
//! impl<Context> X {
//! ..
//! }
//! ```
//!
//! expands to
//!
//! ```ignore
//! impl<Context> X
//! where
//! Context: somewhere::FooSubsystemTrait,
//! Context: support_crate::SubsystemContext,
//! <Context as somewhere::FooContextTrait>::Sender: somewhere::FooSenderTrait,
//! <Context as support_crate::SubsystemContext>::Sender: somewhere::FooSenderTrait,
//! {
//! }
//! ```
//!
//! ### To a free standing `Fn` (not a method, that's covered by the above)
//!
//! ```ignore
//! #[contextbounds(Foo, prefix = somewhere)]
//! fn do_smth<Context>(context: &mut Context) {
//! ..
//! }
//! ```
//!
//! expands to
//!
//! ```ignore
//! fn do_smth<Context>(context: &mut Context)
//! where
//! Context: somewhere::FooSubsystemTrait,
//! Context: support_crate::SubsystemContext,
//! <Context as somewhere::FooContextTrait>::Sender: somewhere::FooSenderTrait,
//! <Context as support_crate::SubsystemContext>::Sender: somewhere::FooSenderTrait,
//! {
//! }
//! ```
use proc_macro2::TokenStream;
use quote::{format_ident, ToTokens};
use syn::{parse2, parse_quote, punctuated::Punctuated, Result};
use super::{parse::*, *};
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) enum MakeSubsystem {
/// Implements `trait Subsystem` and apply the trait bounds to the `Context` generic.
///
/// Relevant to `impl Item` only.
ImplSubsystemTrait,
/// Only apply the trait bounds to the context.
AddContextTraitBounds,
}
pub(crate) fn impl_subsystem_context_trait_bounds(
attr: TokenStream,
orig: TokenStream,
make_subsystem: MakeSubsystem,
) -> Result<proc_macro2::TokenStream> {
let args = parse2::<SubsystemAttrArgs>(attr.clone())?;
let span = args.span();
let SubsystemAttrArgs { error_path, subsystem_ident, trait_prefix_path, .. } = args;
let mut item = parse2::<syn::Item>(orig)?;
// always prefer the direct usage, if it's not there, let's see if there is
// a `prefix=*` provided. Either is ok.
// Technically this is two different things:
// The place where the `#[orchestra]` is annotated is where all `trait *SenderTrait` and
// `trait *ContextTrait` types exist.
// The other usage is the true support crate `orchestra`, where the static ones
// are declared.
// Right now, if the `support_crate` is not included, it falls back silently to the `trait_prefix_path`.
let support_crate = support_crate()
.or_else(|_e| {
trait_prefix_path.clone().ok_or_else(|| {
syn::Error::new(attr.span(), "Couldn't find `orchestra` in manifest, but also missing a `prefix=` to help trait bound resolution")
})
})?;
let trait_prefix_path = trait_prefix_path.unwrap_or_else(|| parse_quote! { self });
if trait_prefix_path.segments.trailing_punct() {
return Err(syn::Error::new(trait_prefix_path.span(), "Must not end with `::`"))
}
let subsystem_ctx_trait = format_ident!("{}ContextTrait", subsystem_ident);
let subsystem_sender_trait = format_ident!("{}SenderTrait", subsystem_ident);
let extra_where_predicates: Punctuated<syn::WherePredicate, syn::Token![,]> = parse_quote! {
Context: #trait_prefix_path::#subsystem_ctx_trait,
Context: #support_crate::SubsystemContext,
<Context as #trait_prefix_path::#subsystem_ctx_trait>::Sender: #trait_prefix_path::#subsystem_sender_trait,
<Context as #support_crate::SubsystemContext>::Sender: #trait_prefix_path::#subsystem_sender_trait,
};
let apply_ctx_bound_if_present = move |generics: &mut syn::Generics| -> bool {
if generics
.params
.iter()
.find(|generic| match generic {
syn::GenericParam::Type(ty) if ty.ident == "Context" => true,
_ => false,
})
.is_some()
{
let where_clause = generics.make_where_clause();
where_clause.predicates.extend(extra_where_predicates.clone());
true
} else {
false
}
};
match item {
syn::Item::Impl(ref mut struktured_impl) => {
if make_subsystem == MakeSubsystem::ImplSubsystemTrait {
let error_path = error_path.ok_or_else(|| {
syn::Error::new(
span,
"Must annotate the identical orchestra error type via `error=..`.",
)
})?;
// Only replace the subsystem trait if it's desired.
struktured_impl.trait_.replace((
None,
parse_quote! {
#support_crate::Subsystem<Context, #error_path>
},
syn::token::For::default(),
));
}
apply_ctx_bound_if_present(&mut struktured_impl.generics);
for item in struktured_impl.items.iter_mut() {
match item {
syn::ImplItem::Method(method) => {
apply_ctx_bound_if_present(&mut method.sig.generics);
},
_others => {
// don't error, just nop
},
}
}
},
syn::Item::Fn(ref mut struktured_fn) => {
if make_subsystem == MakeSubsystem::ImplSubsystemTrait {
return Err(syn::Error::new(struktured_fn.span(), "Cannot make a free function a subsystem, did you mean to apply `contextbound` instead?"));
}
apply_ctx_bound_if_present(&mut struktured_fn.sig.generics);
},
other =>
return Err(syn::Error::new(
other.span(),
"Macro can only be annotated on functions or struct implementations",
)),
};
Ok(item.to_token_stream())
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn is_path() {
let _p: Path = parse_quote! { self };
let _p: Path = parse_quote! { crate };
let _p: Path = parse_quote! { ::foo };
let _p: Path = parse_quote! { bar };
}
}