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Don't bake in Send + 'static.

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Send + 'static was baked in to make it possible to spawn futures onto
the default executor. We can accomplish the same thing by offering
helper fns that do the spawning while not requiring it for the rest of
the functionality.

Fixes https://github.com/google/tarpc/issues/212
This commit is contained in:
Tim Kuehn
2019-07-22 13:13:08 -07:00
committed by Tim
parent 13cb14a119
commit 50879d2acb
15 changed files with 428 additions and 210 deletions
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69
plugins/src/lib.rs
View File

@@ -21,7 +21,7 @@ use syn::{
punctuated::Punctuated,
spanned::Spanned,
token::Comma,
ArgCaptured, Attribute, FnArg, Ident, Pat, ReturnType, Token, Visibility,
ArgCaptured, Attribute, FnArg, Ident, Lit, LitBool, MetaNameValue, Pat, ReturnType, Token, Visibility,
};
struct Service {
@@ -126,6 +126,40 @@ impl Parse for RpcMethod {
}
}
// If `derive_serde` meta item is not present, defaults to cfg!(feature = "serde1").
// `derive_serde` can only be true when serde1 is enabled.
struct DeriveSerde(bool);
impl Parse for DeriveSerde {
fn parse(input: ParseStream) -> syn::Result<Self> {
if input.is_empty() {
return Ok(DeriveSerde(cfg!(feature = "serde1")))
}
match input.parse::<MetaNameValue>()? {
MetaNameValue { ref ident, ref lit, .. } if ident == "derive_serde" => {
match lit {
Lit::Bool(LitBool{value: true, ..}) if cfg!(feature = "serde1") => Ok(DeriveSerde(true)),
Lit::Bool(LitBool{value: true, ..}) => Err(syn::Error::new(
lit.span(),
"To enable serde, first enable the `serde1` feature of tarpc",
)),
Lit::Bool(LitBool{value: false, ..}) => Ok(DeriveSerde(false)),
lit => Err(syn::Error::new(
lit.span(),
"`derive_serde` expects a value of type `bool`",
)),
}
}
MetaNameValue { ident, .. } => {
Err(syn::Error::new(
ident.span(),
"tarpc::service only supports one meta item, `derive_serde = {bool}`",
))
}
}
}
}
/// Generates:
/// - service trait
/// - serve fn
@@ -135,13 +169,7 @@ impl Parse for RpcMethod {
/// - ResponseFut Future
#[proc_macro_attribute]
pub fn service(attr: TokenStream, input: TokenStream) -> TokenStream {
struct EmptyArgs;
impl Parse for EmptyArgs {
fn parse(_: ParseStream) -> syn::Result<Self> {
Ok(EmptyArgs)
}
}
parse_macro_input!(attr as EmptyArgs);
let derive_serde = parse_macro_input!(attr as DeriveSerde);
let Service {
attrs,
@@ -223,14 +251,15 @@ pub fn service(attr: TokenStream, input: TokenStream) -> TokenStream {
let response_fut_ident_repeated2 = response_fut_ident_repeated.clone();
let server_ident = Ident::new(&format!("Serve{}", ident), ident.span());
#[cfg(feature = "serde1")]
let derive_serialize = quote!(#[derive(serde::Serialize, serde::Deserialize)]);
#[cfg(not(feature = "serde1"))]
let derive_serialize = quote!();
let derive_serialize = if derive_serde.0 {
quote!(#[derive(serde::Serialize, serde::Deserialize)])
} else {
quote!()
};
let tokens = quote! {
#( #attrs )*
#vis trait #ident: Clone + Send + 'static {
#vis trait #ident: Clone {
#( #types_and_fns )*
/// Returns a serving function to use with tarpc::server::Server.
@@ -322,12 +351,18 @@ pub fn service(attr: TokenStream, input: TokenStream) -> TokenStream {
impl #client_ident {
/// Returns a new client stub that sends requests over the given transport.
#vis async fn new<T>(config: tarpc::client::Config, transport: T)
-> std::io::Result<Self>
#vis fn new<T>(config: tarpc::client::Config, transport: T)
-> tarpc::client::NewClient<
Self,
tarpc::client::channel::RequestDispatch<#request_ident, #response_ident, T>>
where
T: tarpc::Transport<tarpc::ClientMessage<#request_ident>, tarpc::Response<#response_ident>> + Send + 'static
T: tarpc::Transport<tarpc::ClientMessage<#request_ident>, tarpc::Response<#response_ident>>
{
Ok(#client_ident(tarpc::client::new(config, transport).await?))
let new_client = tarpc::client::new(config, transport);
tarpc::client::NewClient {
client: #client_ident(new_client.client),
dispatch: new_client.dispatch,
}
}
}