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Support reexport for procedural macros #2124

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merged 2 commits into from
Apr 22, 2020
Merged

Support reexport for procedural macros #2124

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53a454b
Support reexport for join!/try_join! macros
taiki-e Apr 10, 2020
16ab45e
Support reexport for select!/select_biased! macros
taiki-e Apr 17, 2020
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3 changes: 3 additions & 0 deletions Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,9 @@ members = [
"futures-util",
"futures-test",

"futures/tests/macro-tests",
"futures/tests/macro-reexport",

"examples/functional",
"examples/imperative",
]
66 changes: 21 additions & 45 deletions futures-macro/src/join.rs
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Expand Up @@ -4,32 +4,17 @@ use proc_macro::TokenStream;
use proc_macro2::{Span, TokenStream as TokenStream2};
use quote::{format_ident, quote};
use syn::parse::{Parse, ParseStream};
use syn::{parenthesized, parse_quote, Expr, Ident, Token};

mod kw {
syn::custom_keyword!(futures_crate_path);
}
use syn::{Expr, Ident, Token};

#[derive(Default)]
struct Join {
futures_crate_path: Option<syn::Path>,
fut_exprs: Vec<Expr>,
}

impl Parse for Join {
fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
let mut join = Join::default();

// When `futures_crate_path(::path::to::futures::lib)` is provided,
// it sets the path through which futures library functions will be
// accessed.
if input.peek(kw::futures_crate_path) {
input.parse::<kw::futures_crate_path>()?;
let content;
parenthesized!(content in input);
join.futures_crate_path = Some(content.parse()?);
}

while !input.is_empty() {
join.fut_exprs.push(input.parse::<Expr>()?);

Expand All @@ -43,7 +28,6 @@ impl Parse for Join {
}

fn bind_futures(
futures_crate: &syn::Path,
fut_exprs: Vec<Expr>,
span: Span,
) -> (Vec<TokenStream2>, Vec<Ident>) {
Expand All @@ -56,7 +40,7 @@ fn bind_futures(
future_let_bindings.push(quote! {
// Move future into a local so that it is pinned in one place and
// is no longer accessible by the end user.
let mut #name = #futures_crate::future::maybe_done(#expr);
let mut #name = __futures_crate::future::maybe_done(#expr);
});
name
})
Expand All @@ -69,39 +53,35 @@ fn bind_futures(
pub(crate) fn join(input: TokenStream) -> TokenStream {
let parsed = syn::parse_macro_input!(input as Join);

let futures_crate = parsed
.futures_crate_path
.unwrap_or_else(|| parse_quote!(::futures_util));

// should be def_site, but that's unstable
let span = Span::call_site();

let (future_let_bindings, future_names) = bind_futures(&futures_crate, parsed.fut_exprs, span);
let (future_let_bindings, future_names) = bind_futures(parsed.fut_exprs, span);

let poll_futures = future_names.iter().map(|fut| {
quote! {
__all_done &= #futures_crate::core_reexport::future::Future::poll(
unsafe { #futures_crate::core_reexport::pin::Pin::new_unchecked(&mut #fut) }, __cx).is_ready();
__all_done &= __futures_crate::future::Future::poll(
unsafe { __futures_crate::core_reexport::pin::Pin::new_unchecked(&mut #fut) }, __cx).is_ready();
}
});
let take_outputs = future_names.iter().map(|fut| {
quote! {
unsafe { #futures_crate::core_reexport::pin::Pin::new_unchecked(&mut #fut) }.take_output().unwrap(),
unsafe { __futures_crate::core_reexport::pin::Pin::new_unchecked(&mut #fut) }.take_output().unwrap(),
}
});

TokenStream::from(quote! { {
#( #future_let_bindings )*

#futures_crate::future::poll_fn(move |__cx: &mut #futures_crate::task::Context<'_>| {
__futures_crate::future::poll_fn(move |__cx: &mut __futures_crate::task::Context<'_>| {
let mut __all_done = true;
#( #poll_futures )*
if __all_done {
#futures_crate::core_reexport::task::Poll::Ready((
__futures_crate::task::Poll::Ready((
#( #take_outputs )*
))
} else {
#futures_crate::core_reexport::task::Poll::Pending
__futures_crate::task::Poll::Pending
}
}).await
} })
Expand All @@ -111,29 +91,25 @@ pub(crate) fn join(input: TokenStream) -> TokenStream {
pub(crate) fn try_join(input: TokenStream) -> TokenStream {
let parsed = syn::parse_macro_input!(input as Join);

let futures_crate = parsed
.futures_crate_path
.unwrap_or_else(|| parse_quote!(::futures_util));

// should be def_site, but that's unstable
let span = Span::call_site();

let (future_let_bindings, future_names) = bind_futures(&futures_crate, parsed.fut_exprs, span);
let (future_let_bindings, future_names) = bind_futures(parsed.fut_exprs, span);

let poll_futures = future_names.iter().map(|fut| {
quote! {
if #futures_crate::core_reexport::future::Future::poll(
unsafe { #futures_crate::core_reexport::pin::Pin::new_unchecked(&mut #fut) }, __cx).is_pending()
if __futures_crate::future::Future::poll(
unsafe { __futures_crate::core_reexport::pin::Pin::new_unchecked(&mut #fut) }, __cx).is_pending()
{
__all_done = false;
} else if unsafe { #futures_crate::core_reexport::pin::Pin::new_unchecked(&mut #fut) }.output_mut().unwrap().is_err() {
} else if unsafe { __futures_crate::core_reexport::pin::Pin::new_unchecked(&mut #fut) }.output_mut().unwrap().is_err() {
// `.err().unwrap()` rather than `.unwrap_err()` so that we don't introduce
// a `T: Debug` bound.
// Also, for an error type of ! any code after `err().unwrap()` is unreachable.
#[allow(unreachable_code)]
return #futures_crate::core_reexport::task::Poll::Ready(
#futures_crate::core_reexport::result::Result::Err(
unsafe { #futures_crate::core_reexport::pin::Pin::new_unchecked(&mut #fut) }.take_output().unwrap().err().unwrap()
return __futures_crate::task::Poll::Ready(
__futures_crate::core_reexport::result::Result::Err(
unsafe { __futures_crate::core_reexport::pin::Pin::new_unchecked(&mut #fut) }.take_output().unwrap().err().unwrap()
)
);
}
Expand All @@ -145,25 +121,25 @@ pub(crate) fn try_join(input: TokenStream) -> TokenStream {
// an `E: Debug` bound.
// Also, for an ok type of ! any code after `ok().unwrap()` is unreachable.
#[allow(unreachable_code)]
unsafe { #futures_crate::core_reexport::pin::Pin::new_unchecked(&mut #fut) }.take_output().unwrap().ok().unwrap(),
unsafe { __futures_crate::core_reexport::pin::Pin::new_unchecked(&mut #fut) }.take_output().unwrap().ok().unwrap(),
}
});

TokenStream::from(quote! { {
#( #future_let_bindings )*

#[allow(clippy::diverging_sub_expression)]
#futures_crate::future::poll_fn(move |__cx: &mut #futures_crate::task::Context<'_>| {
__futures_crate::future::poll_fn(move |__cx: &mut __futures_crate::task::Context<'_>| {
let mut __all_done = true;
#( #poll_futures )*
if __all_done {
#futures_crate::core_reexport::task::Poll::Ready(
#futures_crate::core_reexport::result::Result::Ok((
__futures_crate::task::Poll::Ready(
__futures_crate::core_reexport::result::Result::Ok((
#( #take_outputs )*
))
)
} else {
#futures_crate::core_reexport::task::Poll::Pending
__futures_crate::task::Poll::Pending
}
}).await
} })
Expand Down
8 changes: 4 additions & 4 deletions futures-macro/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -23,24 +23,24 @@ mod select;

/// The `join!` macro.
#[proc_macro_hack]
pub fn join(input: TokenStream) -> TokenStream {
pub fn join_internal(input: TokenStream) -> TokenStream {
crate::join::join(input)
}

/// The `try_join!` macro.
#[proc_macro_hack]
pub fn try_join(input: TokenStream) -> TokenStream {
pub fn try_join_internal(input: TokenStream) -> TokenStream {
crate::join::try_join(input)
}

/// The `select!` macro.
#[proc_macro_hack]
pub fn select(input: TokenStream) -> TokenStream {
pub fn select_internal(input: TokenStream) -> TokenStream {
crate::select::select(input)
}

/// The `select_biased!` macro.
#[proc_macro_hack]
pub fn select_biased(input: TokenStream) -> TokenStream {
pub fn select_biased_internal(input: TokenStream) -> TokenStream {
crate::select::select_biased(input)
}
55 changes: 20 additions & 35 deletions futures-macro/src/select.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,16 +3,14 @@
use proc_macro::TokenStream;
use proc_macro2::Span;
use quote::{format_ident, quote};
use syn::{parenthesized, parse_quote, Expr, Ident, Pat, Token};
use syn::{parse_quote, Expr, Ident, Pat, Token};
use syn::parse::{Parse, ParseStream};

mod kw {
syn::custom_keyword!(complete);
syn::custom_keyword!(futures_crate_path);
}

struct Select {
futures_crate_path: Option<syn::Path>,
// span of `complete`, then expression after `=> ...`
complete: Option<Expr>,
default: Option<Expr>,
Expand All @@ -30,23 +28,12 @@ enum CaseKind {
impl Parse for Select {
fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
let mut select = Select {
futures_crate_path: None,
complete: None,
default: None,
normal_fut_exprs: vec![],
normal_fut_handlers: vec![],
};

// When `futures_crate_path(::path::to::futures::lib)` is provided,
// it sets the path through which futures library functions will be
// accessed.
if input.peek(kw::futures_crate_path) {
input.parse::<kw::futures_crate_path>()?;
let content;
parenthesized!(content in input);
select.futures_crate_path = Some(content.parse()?);
}

while !input.is_empty() {
let case_kind = if input.peek(kw::complete) {
// `complete`
Expand Down Expand Up @@ -147,8 +134,6 @@ pub(crate) fn select_biased(input: TokenStream) -> TokenStream {
fn select_inner(input: TokenStream, random: bool) -> TokenStream {
let parsed = syn::parse_macro_input!(input as Select);

let futures_crate: syn::Path = parsed.futures_crate_path.unwrap_or_else(|| parse_quote!(::futures_util));

// should be def_site, but that's unstable
let span = Span::call_site();

Expand All @@ -175,8 +160,8 @@ fn select_inner(input: TokenStream, random: bool) -> TokenStream {
// We check for this condition here in order to be able to
// safely use Pin::new_unchecked(&mut #path) later on.
future_let_bindings.push(quote! {
#futures_crate::async_await::assert_fused_future(&#path);
#futures_crate::async_await::assert_unpin(&#path);
__futures_crate::async_await::assert_fused_future(&#path);
__futures_crate::async_await::assert_unpin(&#path);
});
path
},
Expand Down Expand Up @@ -214,28 +199,28 @@ fn select_inner(input: TokenStream, random: bool) -> TokenStream {
// 2. The Future is created in scope of the select! function and will
// not be moved for the duration of it. It is thereby stack-pinned
quote! {
let mut #variant_name = |__cx: &mut #futures_crate::task::Context<'_>| {
let mut #variant_name = |__cx: &mut __futures_crate::task::Context<'_>| {
let mut #bound_future_name = unsafe {
::core::pin::Pin::new_unchecked(&mut #bound_future_name)
};
if #futures_crate::future::FusedFuture::is_terminated(&#bound_future_name) {
if __futures_crate::future::FusedFuture::is_terminated(&#bound_future_name) {
None
} else {
Some(#futures_crate::future::FutureExt::poll_unpin(
Some(__futures_crate::future::FutureExt::poll_unpin(
&mut #bound_future_name,
__cx,
).map(#enum_ident::#variant_name))
}
};
let #variant_name: &mut dyn FnMut(
&mut #futures_crate::task::Context<'_>
) -> Option<#futures_crate::task::Poll<_>> = &mut #variant_name;
&mut __futures_crate::task::Context<'_>
) -> Option<__futures_crate::task::Poll<_>> = &mut #variant_name;
}
});

let none_polled = if parsed.complete.is_some() {
quote! {
#futures_crate::task::Poll::Ready(#enum_ident::Complete)
__futures_crate::task::Poll::Ready(#enum_ident::Complete)
}
} else {
quote! {
Expand Down Expand Up @@ -267,21 +252,21 @@ fn select_inner(input: TokenStream, random: bool) -> TokenStream {
let await_select_fut = if parsed.default.is_some() {
// For select! with default this returns the Poll result
quote! {
__poll_fn(&mut #futures_crate::task::Context::from_waker(
#futures_crate::task::noop_waker_ref()
__poll_fn(&mut __futures_crate::task::Context::from_waker(
__futures_crate::task::noop_waker_ref()
))
}
} else {
quote! {
#futures_crate::future::poll_fn(__poll_fn).await
__futures_crate::future::poll_fn(__poll_fn).await
}
};

let execute_result_expr = if let Some(default_expr) = &parsed.default {
// For select! with default __select_result is a Poll, otherwise not
quote! {
match __select_result {
#futures_crate::task::Poll::Ready(result) => match result {
__futures_crate::task::Poll::Ready(result) => match result {
#branches
},
_ => #default_expr
Expand All @@ -297,7 +282,7 @@ fn select_inner(input: TokenStream, random: bool) -> TokenStream {

let shuffle = if random {
quote! {
#futures_crate::async_await::shuffle(&mut __select_arr);
__futures_crate::async_await::shuffle(&mut __select_arr);
}
} else {
quote!()
Expand All @@ -309,7 +294,7 @@ fn select_inner(input: TokenStream, random: bool) -> TokenStream {
let __select_result = {
#( #future_let_bindings )*

let mut __poll_fn = |__cx: &mut #futures_crate::task::Context<'_>| {
let mut __poll_fn = |__cx: &mut __futures_crate::task::Context<'_>| {
let mut __any_polled = false;

#( #poll_functions )*
Expand All @@ -318,12 +303,12 @@ fn select_inner(input: TokenStream, random: bool) -> TokenStream {
#shuffle
for poller in &mut __select_arr {
let poller: &mut &mut dyn FnMut(
&mut #futures_crate::task::Context<'_>
) -> Option<#futures_crate::task::Poll<_>> = poller;
&mut __futures_crate::task::Context<'_>
) -> Option<__futures_crate::task::Poll<_>> = poller;
match poller(__cx) {
Some(x @ #futures_crate::task::Poll::Ready(_)) =>
Some(x @ __futures_crate::task::Poll::Ready(_)) =>
return x,
Some(#futures_crate::task::Poll::Pending) => {
Some(__futures_crate::task::Poll::Pending) => {
__any_polled = true;
}
None => {}
Expand All @@ -333,7 +318,7 @@ fn select_inner(input: TokenStream, random: bool) -> TokenStream {
if !__any_polled {
#none_polled
} else {
#futures_crate::task::Poll::Pending
__futures_crate::task::Poll::Pending
}
};

Expand Down
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