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use proc_macro2::{Span, TokenStream, TokenTree};
use quote::{quote, quote_spanned, ToTokens};
use syn::parse::{Parse, ParseStream, Parser};
use syn::{braced, Attribute, Ident, Path, Signature, Visibility};
// syn::AttributeArgs does not implement syn::Parse
type AttributeArgs = syn::punctuated::Punctuated<syn::Meta, syn::Token![,]>;
#[derive(Clone, Copy, PartialEq)]
enum RuntimeFlavor {
CurrentThread,
Threaded,
}
impl RuntimeFlavor {
fn from_str(s: &str) -> Result<RuntimeFlavor, String> {
match s {
"current_thread" => Ok(RuntimeFlavor::CurrentThread),
"multi_thread" => Ok(RuntimeFlavor::Threaded),
"single_thread" => Err("The single threaded runtime flavor is called `current_thread`.".to_string()),
"basic_scheduler" => Err("The `basic_scheduler` runtime flavor has been renamed to `current_thread`.".to_string()),
"threaded_scheduler" => Err("The `threaded_scheduler` runtime flavor has been renamed to `multi_thread`.".to_string()),
_ => Err(format!("No such runtime flavor `{}`. The runtime flavors are `current_thread` and `multi_thread`.", s)),
}
}
}
#[derive(Clone, Copy, PartialEq)]
enum UnhandledPanic {
Ignore,
ShutdownRuntime,
}
impl UnhandledPanic {
fn from_str(s: &str) -> Result<UnhandledPanic, String> {
match s {
"ignore" => Ok(UnhandledPanic::Ignore),
"shutdown_runtime" => Ok(UnhandledPanic::ShutdownRuntime),
_ => Err(format!("No such unhandled panic behavior `{}`. The unhandled panic behaviors are `ignore` and `shutdown_runtime`.", s)),
}
}
fn into_tokens(self, crate_path: &TokenStream) -> TokenStream {
match self {
UnhandledPanic::Ignore => quote! { #crate_path::runtime::UnhandledPanic::Ignore },
UnhandledPanic::ShutdownRuntime => {
quote! { #crate_path::runtime::UnhandledPanic::ShutdownRuntime }
}
}
}
}
struct FinalConfig {
flavor: RuntimeFlavor,
worker_threads: Option<usize>,
start_paused: Option<bool>,
crate_name: Option<Path>,
unhandled_panic: Option<UnhandledPanic>,
}
/// Config used in case of the attribute not being able to build a valid config
const DEFAULT_ERROR_CONFIG: FinalConfig = FinalConfig {
flavor: RuntimeFlavor::CurrentThread,
worker_threads: None,
start_paused: None,
crate_name: None,
unhandled_panic: None,
};
struct Configuration {
rt_multi_thread_available: bool,
default_flavor: RuntimeFlavor,
flavor: Option<RuntimeFlavor>,
worker_threads: Option<(usize, Span)>,
start_paused: Option<(bool, Span)>,
is_test: bool,
crate_name: Option<Path>,
unhandled_panic: Option<(UnhandledPanic, Span)>,
}
impl Configuration {
fn new(is_test: bool, rt_multi_thread: bool) -> Self {
Configuration {
rt_multi_thread_available: rt_multi_thread,
default_flavor: match is_test {
true => RuntimeFlavor::CurrentThread,
false => RuntimeFlavor::Threaded,
},
flavor: None,
worker_threads: None,
start_paused: None,
is_test,
crate_name: None,
unhandled_panic: None,
}
}
fn set_flavor(&mut self, runtime: syn::Lit, span: Span) -> Result<(), syn::Error> {
if self.flavor.is_some() {
return Err(syn::Error::new(span, "`flavor` set multiple times."));
}
let runtime_str = parse_string(runtime, span, "flavor")?;
let runtime =
RuntimeFlavor::from_str(&runtime_str).map_err(|err| syn::Error::new(span, err))?;
self.flavor = Some(runtime);
Ok(())
}
fn set_worker_threads(
&mut self,
worker_threads: syn::Lit,
span: Span,
) -> Result<(), syn::Error> {
if self.worker_threads.is_some() {
return Err(syn::Error::new(
span,
"`worker_threads` set multiple times.",
));
}
let worker_threads = parse_int(worker_threads, span, "worker_threads")?;
if worker_threads == 0 {
return Err(syn::Error::new(span, "`worker_threads` may not be 0."));
}
self.worker_threads = Some((worker_threads, span));
Ok(())
}
fn set_start_paused(&mut self, start_paused: syn::Lit, span: Span) -> Result<(), syn::Error> {
if self.start_paused.is_some() {
return Err(syn::Error::new(span, "`start_paused` set multiple times."));
}
let start_paused = parse_bool(start_paused, span, "start_paused")?;
self.start_paused = Some((start_paused, span));
Ok(())
}
fn set_crate_name(&mut self, name: syn::Lit, span: Span) -> Result<(), syn::Error> {
if self.crate_name.is_some() {
return Err(syn::Error::new(span, "`crate` set multiple times."));
}
let name_path = parse_path(name, span, "crate")?;
self.crate_name = Some(name_path);
Ok(())
}
fn set_unhandled_panic(
&mut self,
unhandled_panic: syn::Lit,
span: Span,
) -> Result<(), syn::Error> {
if self.unhandled_panic.is_some() {
return Err(syn::Error::new(
span,
"`unhandled_panic` set multiple times.",
));
}
let unhandled_panic = parse_string(unhandled_panic, span, "unhandled_panic")?;
let unhandled_panic =
UnhandledPanic::from_str(&unhandled_panic).map_err(|err| syn::Error::new(span, err))?;
self.unhandled_panic = Some((unhandled_panic, span));
Ok(())
}
fn macro_name(&self) -> &'static str {
if self.is_test {
"tokio::test"
} else {
"tokio::main"
}
}
fn build(&self) -> Result<FinalConfig, syn::Error> {
use RuntimeFlavor as F;
let flavor = self.flavor.unwrap_or(self.default_flavor);
let worker_threads = match (flavor, self.worker_threads) {
(F::CurrentThread, Some((_, worker_threads_span))) => {
let msg = format!(
"The `worker_threads` option requires the `multi_thread` runtime flavor. Use `#[{}(flavor = \"multi_thread\")]`",
self.macro_name(),
);
return Err(syn::Error::new(worker_threads_span, msg));
}
(F::CurrentThread, None) => None,
(F::Threaded, worker_threads) if self.rt_multi_thread_available => {
worker_threads.map(|(val, _span)| val)
}
(F::Threaded, _) => {
let msg = if self.flavor.is_none() {
"The default runtime flavor is `multi_thread`, but the `rt-multi-thread` feature is disabled."
} else {
"The runtime flavor `multi_thread` requires the `rt-multi-thread` feature."
};
return Err(syn::Error::new(Span::call_site(), msg));
}
};
let start_paused = match (flavor, self.start_paused) {
(F::Threaded, Some((_, start_paused_span))) => {
let msg = format!(
"The `start_paused` option requires the `current_thread` runtime flavor. Use `#[{}(flavor = \"current_thread\")]`",
self.macro_name(),
);
return Err(syn::Error::new(start_paused_span, msg));
}
(F::CurrentThread, Some((start_paused, _))) => Some(start_paused),
(_, None) => None,
};
let unhandled_panic = match (flavor, self.unhandled_panic) {
(F::Threaded, Some((_, unhandled_panic_span))) => {
let msg = format!(
"The `unhandled_panic` option requires the `current_thread` runtime flavor. Use `#[{}(flavor = \"current_thread\")]`",
self.macro_name(),
);
return Err(syn::Error::new(unhandled_panic_span, msg));
}
(F::CurrentThread, Some((unhandled_panic, _))) => Some(unhandled_panic),
(_, None) => None,
};
Ok(FinalConfig {
crate_name: self.crate_name.clone(),
flavor,
worker_threads,
start_paused,
unhandled_panic,
})
}
}
fn parse_int(int: syn::Lit, span: Span, field: &str) -> Result<usize, syn::Error> {
match int {
syn::Lit::Int(lit) => match lit.base10_parse::<usize>() {
Ok(value) => Ok(value),
Err(e) => Err(syn::Error::new(
span,
format!("Failed to parse value of `{}` as integer: {}", field, e),
)),
},
_ => Err(syn::Error::new(
span,
format!("Failed to parse value of `{}` as integer.", field),
)),
}
}
fn parse_string(int: syn::Lit, span: Span, field: &str) -> Result<String, syn::Error> {
match int {
syn::Lit::Str(s) => Ok(s.value()),
syn::Lit::Verbatim(s) => Ok(s.to_string()),
_ => Err(syn::Error::new(
span,
format!("Failed to parse value of `{}` as string.", field),
)),
}
}
fn parse_path(lit: syn::Lit, span: Span, field: &str) -> Result<Path, syn::Error> {
match lit {
syn::Lit::Str(s) => {
let err = syn::Error::new(
span,
format!(
"Failed to parse value of `{}` as path: \"{}\"",
field,
s.value()
),
);
s.parse::<syn::Path>().map_err(|_| err.clone())
}
_ => Err(syn::Error::new(
span,
format!("Failed to parse value of `{}` as path.", field),
)),
}
}
fn parse_bool(bool: syn::Lit, span: Span, field: &str) -> Result<bool, syn::Error> {
match bool {
syn::Lit::Bool(b) => Ok(b.value),
_ => Err(syn::Error::new(
span,
format!("Failed to parse value of `{}` as bool.", field),
)),
}
}
fn build_config(
input: &ItemFn,
args: AttributeArgs,
is_test: bool,
rt_multi_thread: bool,
) -> Result<FinalConfig, syn::Error> {
if input.sig.asyncness.is_none() {
let msg = "the `async` keyword is missing from the function declaration";
return Err(syn::Error::new_spanned(input.sig.fn_token, msg));
}
let mut config = Configuration::new(is_test, rt_multi_thread);
let macro_name = config.macro_name();
for arg in args {
match arg {
syn::Meta::NameValue(namevalue) => {
let ident = namevalue
.path
.get_ident()
.ok_or_else(|| {
syn::Error::new_spanned(&namevalue, "Must have specified ident")
})?
.to_string()
.to_lowercase();
let lit = match &namevalue.value {
syn::Expr::Lit(syn::ExprLit { lit, .. }) => lit,
expr => return Err(syn::Error::new_spanned(expr, "Must be a literal")),
};
match ident.as_str() {
"worker_threads" => {
config.set_worker_threads(lit.clone(), syn::spanned::Spanned::span(lit))?;
}
"flavor" => {
config.set_flavor(lit.clone(), syn::spanned::Spanned::span(lit))?;
}
"start_paused" => {
config.set_start_paused(lit.clone(), syn::spanned::Spanned::span(lit))?;
}
"core_threads" => {
let msg = "Attribute `core_threads` is renamed to `worker_threads`";
return Err(syn::Error::new_spanned(namevalue, msg));
}
"crate" => {
config.set_crate_name(lit.clone(), syn::spanned::Spanned::span(lit))?;
}
"unhandled_panic" => {
config
.set_unhandled_panic(lit.clone(), syn::spanned::Spanned::span(lit))?;
}
name => {
let msg = format!(
"Unknown attribute {} is specified; expected one of: `flavor`, `worker_threads`, `start_paused`, `crate`, `unhandled_panic`",
name,
);
return Err(syn::Error::new_spanned(namevalue, msg));
}
}
}
syn::Meta::Path(path) => {
let name = path
.get_ident()
.ok_or_else(|| syn::Error::new_spanned(&path, "Must have specified ident"))?
.to_string()
.to_lowercase();
let msg = match name.as_str() {
"threaded_scheduler" | "multi_thread" => {
format!(
"Set the runtime flavor with #[{}(flavor = \"multi_thread\")].",
macro_name
)
}
"basic_scheduler" | "current_thread" | "single_threaded" => {
format!(
"Set the runtime flavor with #[{}(flavor = \"current_thread\")].",
macro_name
)
}
"flavor" | "worker_threads" | "start_paused" | "crate" | "unhandled_panic" => {
format!("The `{}` attribute requires an argument.", name)
}
name => {
format!("Unknown attribute {} is specified; expected one of: `flavor`, `worker_threads`, `start_paused`, `crate`, `unhandled_panic`.", name)
}
};
return Err(syn::Error::new_spanned(path, msg));
}
other => {
return Err(syn::Error::new_spanned(
other,
"Unknown attribute inside the macro",
));
}
}
}
config.build()
}
fn parse_knobs(mut input: ItemFn, is_test: bool, config: FinalConfig) -> TokenStream {
input.sig.asyncness = None;
// If type mismatch occurs, the current rustc points to the last statement.
let (last_stmt_start_span, last_stmt_end_span) = {
let mut last_stmt = input.stmts.last().cloned().unwrap_or_default().into_iter();
// `Span` on stable Rust has a limitation that only points to the first
// token, not the whole tokens. We can work around this limitation by
// using the first/last span of the tokens like
// `syn::Error::new_spanned` does.
let start = last_stmt.next().map_or_else(Span::call_site, |t| t.span());
let end = last_stmt.last().map_or(start, |t| t.span());
(start, end)
};
let crate_path = config
.crate_name
.map(ToTokens::into_token_stream)
.unwrap_or_else(|| Ident::new("tokio", last_stmt_start_span).into_token_stream());
let mut rt = match config.flavor {
RuntimeFlavor::CurrentThread => quote_spanned! {last_stmt_start_span=>
#crate_path::runtime::Builder::new_current_thread()
},
RuntimeFlavor::Threaded => quote_spanned! {last_stmt_start_span=>
#crate_path::runtime::Builder::new_multi_thread()
},
};
if let Some(v) = config.worker_threads {
rt = quote_spanned! {last_stmt_start_span=> #rt.worker_threads(#v) };
}
if let Some(v) = config.start_paused {
rt = quote_spanned! {last_stmt_start_span=> #rt.start_paused(#v) };
}
if let Some(v) = config.unhandled_panic {
let unhandled_panic = v.into_tokens(&crate_path);
rt = quote_spanned! {last_stmt_start_span=> #rt.unhandled_panic(#unhandled_panic) };
}
let generated_attrs = if is_test {
quote! {
#[::core::prelude::v1::test]
}
} else {
quote! {}
};
let body_ident = quote! { body };
let last_block = quote_spanned! {last_stmt_end_span=>
#[allow(clippy::expect_used, clippy::diverging_sub_expression)]
{
return #rt
.enable_all()
.build()
.expect("Failed building the Runtime")
.block_on(#body_ident);
}
};
let body = input.body();
// For test functions pin the body to the stack and use `Pin<&mut dyn
// Future>` to reduce the amount of `Runtime::block_on` (and related
// functions) copies we generate during compilation due to the generic
// parameter `F` (the future to block on). This could have an impact on
// performance, but because it's only for testing it's unlikely to be very
// large.
//
// We don't do this for the main function as it should only be used once so
// there will be no benefit.
let body = if is_test {
let output_type = match &input.sig.output {
// For functions with no return value syn doesn't print anything,
// but that doesn't work as `Output` for our boxed `Future`, so
// default to `()` (the same type as the function output).
syn::ReturnType::Default => quote! { () },
syn::ReturnType::Type(_, ret_type) => quote! { #ret_type },
};
quote! {
let body = async #body;
#crate_path::pin!(body);
let body: ::core::pin::Pin<&mut dyn ::core::future::Future<Output = #output_type>> = body;
}
} else {
quote! {
let body = async #body;
}
};
input.into_tokens(generated_attrs, body, last_block)
}
fn token_stream_with_error(mut tokens: TokenStream, error: syn::Error) -> TokenStream {
tokens.extend(error.into_compile_error());
tokens
}
pub(crate) fn main(args: TokenStream, item: TokenStream, rt_multi_thread: bool) -> TokenStream {
// If any of the steps for this macro fail, we still want to expand to an item that is as close
// to the expected output as possible. This helps out IDEs such that completions and other
// related features keep working.
let input: ItemFn = match syn::parse2(item.clone()) {
Ok(it) => it,
Err(e) => return token_stream_with_error(item, e),
};
let config = if input.sig.ident == "main" && !input.sig.inputs.is_empty() {
let msg = "the main function cannot accept arguments";
Err(syn::Error::new_spanned(&input.sig.ident, msg))
} else {
AttributeArgs::parse_terminated
.parse2(args)
.and_then(|args| build_config(&input, args, false, rt_multi_thread))
};
match config {
Ok(config) => parse_knobs(input, false, config),
Err(e) => token_stream_with_error(parse_knobs(input, false, DEFAULT_ERROR_CONFIG), e),
}
}
// Check whether given attribute is a test attribute of forms:
// * `#[test]`
// * `#[core::prelude::*::test]` or `#[::core::prelude::*::test]`
// * `#[std::prelude::*::test]` or `#[::std::prelude::*::test]`
fn is_test_attribute(attr: &Attribute) -> bool {
let path = match &attr.meta {
syn::Meta::Path(path) => path,
_ => return false,
};
let candidates = [
["core", "prelude", "*", "test"],
["std", "prelude", "*", "test"],
];
if path.leading_colon.is_none()
&& path.segments.len() == 1
&& path.segments[0].arguments.is_none()
&& path.segments[0].ident == "test"
{
return true;
} else if path.segments.len() != candidates[0].len() {
return false;
}
candidates.into_iter().any(|segments| {
path.segments.iter().zip(segments).all(|(segment, path)| {
segment.arguments.is_none() && (path == "*" || segment.ident == path)
})
})
}
pub(crate) fn test(args: TokenStream, item: TokenStream, rt_multi_thread: bool) -> TokenStream {
// If any of the steps for this macro fail, we still want to expand to an item that is as close
// to the expected output as possible. This helps out IDEs such that completions and other
// related features keep working.
let input: ItemFn = match syn::parse2(item.clone()) {
Ok(it) => it,
Err(e) => return token_stream_with_error(item, e),
};
let config = if let Some(attr) = input.attrs().find(|attr| is_test_attribute(attr)) {
let msg = "second test attribute is supplied, consider removing or changing the order of your test attributes";
Err(syn::Error::new_spanned(attr, msg))
} else {
AttributeArgs::parse_terminated
.parse2(args)
.and_then(|args| build_config(&input, args, true, rt_multi_thread))
};
match config {
Ok(config) => parse_knobs(input, true, config),
Err(e) => token_stream_with_error(parse_knobs(input, true, DEFAULT_ERROR_CONFIG), e),
}
}
struct ItemFn {
outer_attrs: Vec<Attribute>,
vis: Visibility,
sig: Signature,
brace_token: syn::token::Brace,
inner_attrs: Vec<Attribute>,
stmts: Vec<proc_macro2::TokenStream>,
}
impl ItemFn {
/// Access all attributes of the function item.
fn attrs(&self) -> impl Iterator<Item = &Attribute> {
self.outer_attrs.iter().chain(self.inner_attrs.iter())
}
/// Get the body of the function item in a manner so that it can be
/// conveniently used with the `quote!` macro.
fn body(&self) -> Body<'_> {
Body {
brace_token: self.brace_token,
stmts: &self.stmts,
}
}
/// Convert our local function item into a token stream.
fn into_tokens(
self,
generated_attrs: proc_macro2::TokenStream,
body: proc_macro2::TokenStream,
last_block: proc_macro2::TokenStream,
) -> TokenStream {
let mut tokens = proc_macro2::TokenStream::new();
// Outer attributes are simply streamed as-is.
for attr in self.outer_attrs {
attr.to_tokens(&mut tokens);
}
// Inner attributes require extra care, since they're not supported on
// blocks (which is what we're expanded into) we instead lift them
// outside of the function. This matches the behavior of `syn`.
for mut attr in self.inner_attrs {
attr.style = syn::AttrStyle::Outer;
attr.to_tokens(&mut tokens);
}
// Add generated macros at the end, so macros processed later are aware of them.
generated_attrs.to_tokens(&mut tokens);
self.vis.to_tokens(&mut tokens);
self.sig.to_tokens(&mut tokens);
self.brace_token.surround(&mut tokens, |tokens| {
body.to_tokens(tokens);
last_block.to_tokens(tokens);
});
tokens
}
}
impl Parse for ItemFn {
#[inline]
fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
// This parse implementation has been largely lifted from `syn`, with
// the exception of:
// * We don't have access to the plumbing necessary to parse inner
// attributes in-place.
// * We do our own statements parsing to avoid recursively parsing
// entire statements and only look for the parts we're interested in.
let outer_attrs = input.call(Attribute::parse_outer)?;
let vis: Visibility = input.parse()?;
let sig: Signature = input.parse()?;
let content;
let brace_token = braced!(content in input);
let inner_attrs = Attribute::parse_inner(&content)?;
let mut buf = proc_macro2::TokenStream::new();
let mut stmts = Vec::new();
while !content.is_empty() {
if let Some(semi) = content.parse::<Option<syn::Token![;]>>()? {
semi.to_tokens(&mut buf);
stmts.push(buf);
buf = proc_macro2::TokenStream::new();
continue;
}
// Parse a single token tree and extend our current buffer with it.
// This avoids parsing the entire content of the sub-tree.
buf.extend([content.parse::<TokenTree>()?]);
}
if !buf.is_empty() {
stmts.push(buf);
}
Ok(Self {
outer_attrs,
vis,
sig,
brace_token,
inner_attrs,
stmts,
})
}
}
struct Body<'a> {
brace_token: syn::token::Brace,
// Statements, with terminating `;`.
stmts: &'a [TokenStream],
}
impl ToTokens for Body<'_> {
fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
self.brace_token.surround(tokens, |tokens| {
for stmt in self.stmts {
stmt.to_tokens(tokens);
}
});
}
}