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Added a way to opt out of error handling for ThreadsafeFunctions.

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This is to allow having the `ThreadSafeFunction` expect the same calling API
as an unwrapped `JsFunction` would have: in some contexts this consistency is
more desireable than giving the option to the caller to handle a native-to-js
conversion failure (or somebody having directly fed a `Result<T>`; although
that use case seems oddly niche to me: it can already be covered when
`type T = Result<U>;` and propagated/flattened inside the `R` closure with a
simple `?`), since such failure can already be quite fatal / unexpected in
some cases.

In order to keep the code backwards-compatible, this PR uses an added
**optional** generic (type) parameter. Since this parameter, semantically,
represents an `enum`, and since we don't have yet `const_generic` `enum`s, we
circumvent this limitation by using the type-level enum pattern, which is
abtracted away with a helper macro that incidentally yields some handy docs
(I can attach a rendered version of the docs hosted on netlify if the reviewer
so wishes).
This commit is contained in:
Daniel Henry-Mantilla 2021-03-09 23:24:53 +01:00
parent 510e584750
commit 0204ef9342
1 changed files with 229 additions and 47 deletions
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276
napi/src/threadsafe_function.rs
View file

@ -36,6 +36,68 @@ impl Into<napi_threadsafe_function_call_mode> for ThreadsafeFunctionCallMode {
}
}
type_level_enum! {
/// Type-level `enum` to express how to feed [`ThreadsafeFunction`] errors to
/// the inner [`JsFunction`].
///
/// ### Context
///
/// For callbacks that expect a `Result`-like kind of input, the convention is
/// to have the callback take an `error` parameter as its first parameter.
///
/// This way receiving a `Result<Args…>` can be modelled as follows:
///
/// - In case of `Err(error)`, feed that `error` entity as the first parameter
/// of the callback;
///
/// - Otherwise (in case of `Ok(_)`), feed `null` instead.
///
/// In pseudo-code:
///
/// ```rust,ignore
/// match result_args {
/// Ok(args) => {
/// let js_null = /* … */;
/// callback.call(
/// // this
/// None,
/// // args…
/// &iter::once(js_null).chain(args).collect::<Vec<_>>(),
/// )
/// },
/// Err(err) => callback.call(None, &[JsError::from(err)]),
/// }
/// ```
///
/// **Note that the `Err` case can stem from a failed conversion from native
/// values to js values when calling the callback!**
///
/// That's why:
///
/// > **[This][`ErrorStrategy::CalleeHandled`] is the default error strategy**.
///
/// In order to opt-out of it, [`ThreadsafeFunction`] has an optional second
/// generic parameter (of "kind" [`ErrorStrategy::T`]) that defines whether
/// this behavior ([`ErrorStrategy::CalleeHandled`]) or a non-`Result` one
/// ([`ErrorStrategy::Fatal`]) is desired.
pub enum ErrorStrategy {
/// Input errors (including conversion errors) are left for the callee to
/// handle:
///
/// The callee receives an extra `error` parameter (the first one), which is
/// `null` if no error occurred, and the error payload otherwise.
CalleeHandled,
/// Input errors (including conversion errors) are deemed fatal:
///
/// they can thus cause a `panic!` or abort the process.
///
/// The callee thus is not expected to have to deal with [that extra `error`
/// parameter][CalleeHandled], which is thus not added.
Fatal,
}
}
/// Communicate with the addon's main thread by invoking a JavaScript function from other threads.
///
/// ## Example
@ -85,13 +147,13 @@ impl Into<napi_threadsafe_function_call_mode> for ThreadsafeFunctionCallMode {
/// ctx.env.get_undefined()
/// }
/// ```
pub struct ThreadsafeFunction<T: 'static> {
pub struct ThreadsafeFunction<T: 'static, ES: ErrorStrategy::T = ErrorStrategy::CalleeHandled> {
raw_tsfn: sys::napi_threadsafe_function,
aborted: Arc<AtomicBool>,
_phantom: PhantomData<T>,
_phantom: PhantomData<(T, ES)>,
}
impl<T: 'static> Clone for ThreadsafeFunction<T> {
impl<T: 'static, ES: ErrorStrategy::T> Clone for ThreadsafeFunction<T, ES> {
fn clone(&self) -> Self {
if !self.aborted.load(Ordering::Acquire) {
let acquire_status = unsafe { sys::napi_acquire_threadsafe_function(self.raw_tsfn) };
@ -109,14 +171,10 @@ impl<T: 'static> Clone for ThreadsafeFunction<T> {
}
}
unsafe impl<T> Send for ThreadsafeFunction<T> {}
unsafe impl<T> Sync for ThreadsafeFunction<T> {}
unsafe impl<T, ES: ErrorStrategy::T> Send for ThreadsafeFunction<T, ES> {}
unsafe impl<T, ES: ErrorStrategy::T> Sync for ThreadsafeFunction<T, ES> {}
struct ThreadSafeContext<T: 'static, V: NapiValue>(
Box<dyn FnMut(ThreadSafeCallContext<T>) -> Result<Vec<V>>>,
);
impl<T: 'static> ThreadsafeFunction<T> {
impl<T: 'static, ES: ErrorStrategy::T> ThreadsafeFunction<T, ES> {
/// See [napi_create_threadsafe_function](https://nodejs.org/api/n-api.html#n_api_napi_create_threadsafe_function)
/// for more information.
#[inline]
@ -139,8 +197,7 @@ impl<T: 'static> ThreadsafeFunction<T> {
let initial_thread_count = 1usize;
let mut raw_tsfn = ptr::null_mut();
let context = ThreadSafeContext(Box::from(callback));
let ptr = Box::into_raw(Box::new(context)) as *mut _;
let ptr = Box::into_raw(Box::new(callback)) as *mut _;
check_status!(unsafe {
sys::napi_create_threadsafe_function(
env,
@ -150,9 +207,9 @@ impl<T: 'static> ThreadsafeFunction<T> {
max_queue_size,
initial_thread_count,
ptr,
Some(thread_finalize_cb::<T, V>),
Some(thread_finalize_cb::<T, V, R>),
ptr,
Some(call_js_cb::<T, V>),
Some(call_js_cb::<T, V, R, ES>),
&mut raw_tsfn,
)
})?;
@ -164,22 +221,6 @@ impl<T: 'static> ThreadsafeFunction<T> {
})
}
/// See [napi_call_threadsafe_function](https://nodejs.org/api/n-api.html#n_api_napi_call_threadsafe_function)
/// for more information.
pub fn call(&self, value: Result<T>, mode: ThreadsafeFunctionCallMode) -> Status {
if self.aborted.load(Ordering::Acquire) {
return Status::Closing;
}
unsafe {
sys::napi_call_threadsafe_function(
self.raw_tsfn,
Box::into_raw(Box::new(value)) as *mut _,
mode.into(),
)
}
.into()
}
/// See [napi_ref_threadsafe_function](https://nodejs.org/api/n-api.html#n_api_napi_ref_threadsafe_function)
/// for more information.
///
@ -227,7 +268,43 @@ impl<T: 'static> ThreadsafeFunction<T> {
}
}
impl<T: 'static> Drop for ThreadsafeFunction<T> {
impl<T: 'static> ThreadsafeFunction<T, ErrorStrategy::CalleeHandled> {
/// See [napi_call_threadsafe_function](https://nodejs.org/api/n-api.html#n_api_napi_call_threadsafe_function)
/// for more information.
pub fn call(&self, value: Result<T>, mode: ThreadsafeFunctionCallMode) -> Status {
if self.aborted.load(Ordering::Acquire) {
return Status::Closing;
}
unsafe {
sys::napi_call_threadsafe_function(
self.raw_tsfn,
Box::into_raw(Box::new(value)) as *mut _,
mode.into(),
)
}
.into()
}
}
impl<T: 'static> ThreadsafeFunction<T, ErrorStrategy::Fatal> {
/// See [napi_call_threadsafe_function](https://nodejs.org/api/n-api.html#n_api_napi_call_threadsafe_function)
/// for more information.
pub fn call(&self, value: T, mode: ThreadsafeFunctionCallMode) -> Status {
if self.aborted.load(Ordering::Acquire) {
return Status::Closing;
}
unsafe {
sys::napi_call_threadsafe_function(
self.raw_tsfn,
Box::into_raw(Box::new(value)) as *mut _,
mode.into(),
)
}
.into()
}
}
impl<T: 'static, ES: ErrorStrategy::T> Drop for ThreadsafeFunction<T, ES> {
fn drop(&mut self) {
if !self.aborted.load(Ordering::Acquire) {
let release_status = unsafe {
@ -244,29 +321,37 @@ impl<T: 'static> Drop for ThreadsafeFunction<T> {
}
}
unsafe extern "C" fn thread_finalize_cb<T: 'static, V: NapiValue>(
unsafe extern "C" fn thread_finalize_cb<T: 'static, V: NapiValue, R>(
_raw_env: sys::napi_env,
finalize_data: *mut c_void,
_finalize_hint: *mut c_void,
) {
) where
R: 'static + Send + FnMut(ThreadSafeCallContext<T>) -> Result<Vec<V>>,
{
// cleanup
Box::from_raw(finalize_data as *mut ThreadSafeContext<T, V>);
drop(Box::<R>::from_raw(finalize_data.cast()));
}
unsafe extern "C" fn call_js_cb<T: 'static, V: NapiValue>(
unsafe extern "C" fn call_js_cb<T: 'static, V: NapiValue, R, ES>(
raw_env: sys::napi_env,
js_callback: sys::napi_value,
context: *mut c_void,
data: *mut c_void,
) {
) where
R: 'static + Send + FnMut(ThreadSafeCallContext<T>) -> Result<Vec<V>>,
ES: ErrorStrategy::T,
{
let ctx: &mut R = &mut *context.cast::<R>();
let val: Result<T> = match ES::VALUE {
ErrorStrategy::CalleeHandled::VALUE => *Box::<Result<T>>::from_raw(data.cast()),
ErrorStrategy::Fatal::VALUE => Ok(*Box::<T>::from_raw(data.cast())),
};
let mut recv = ptr::null_mut();
sys::napi_get_undefined(raw_env, &mut recv);
let ctx = Box::leak(Box::from_raw(context as *mut ThreadSafeContext<T, V>));
let val = Box::from_raw(data as *mut Result<T>);
let ret = val.and_then(|v| {
(ctx.0)(ThreadSafeCallContext {
(ctx)(ThreadSafeCallContext {
env: Env::from_raw(raw_env),
value: v,
})
@ -279,21 +364,26 @@ unsafe extern "C" fn call_js_cb<T: 'static, V: NapiValue>(
// If the Result is an error, pass that as the first argument.
match ret {
Ok(values) => {
let mut js_null = ptr::null_mut();
sys::napi_get_null(raw_env, &mut js_null);
let args_length = values.len() + 1;
let mut args: Vec<sys::napi_value> = Vec::with_capacity(args_length);
args.push(js_null);
args.extend(values.iter().map(|v| v.raw()));
let values = values.iter().map(|v| v.raw());
let args: Vec<sys::napi_value> = if ES::VALUE == ErrorStrategy::CalleeHandled::VALUE {
let mut js_null = ptr::null_mut();
sys::napi_get_null(raw_env, &mut js_null);
::core::iter::once(js_null).chain(values).collect()
} else {
values.collect()
};
status = sys::napi_call_function(
raw_env,
recv,
js_callback,
args_length,
args.len(),
args.as_ptr(),
ptr::null_mut(),
);
}
Err(e) if ES::VALUE == ErrorStrategy::Fatal::VALUE => {
panic!("{:?}", e);
}
Err(e) => {
status = sys::napi_call_function(
raw_env,
@ -350,3 +440,95 @@ unsafe extern "C" fn call_js_cb<T: 'static, V: NapiValue>(
);
}
}
/// Helper
macro_rules! type_level_enum {(
$( #[doc = $doc:tt] )*
$pub:vis
enum $EnumName:ident {
$(
$( #[doc = $doc_variant:tt] )*
$Variant:ident
),* $(,)?
}
) => (type_level_enum! { // This requires the macro to be in scope when called.
with_docs! {
$( #[doc = $doc] )*
///
/// ### Type-level `enum`
///
/// Until `const_generics` can handle custom `enum`s, this pattern must be
/// implemented at the type level.
///
/// We thus end up with:
///
/// ```rust,ignore
/// #[type_level_enum]
#[doc = ::core::concat!(
" enum ", ::core::stringify!($EnumName), " {",
)]
$(
#[doc = ::core::concat!(
" ", ::core::stringify!($Variant), ",",
)]
)*
#[doc = " }"]
/// ```
///
#[doc = ::core::concat!(
"With [`", ::core::stringify!($EnumName), "::T`](#reexports) \
being the type-level \"enum type\":",
)]
///
/// ```rust,ignore
#[doc = ::core::concat!(
"<Param: ", ::core::stringify!($EnumName), "::T>"
)]
/// ```
}
#[allow(warnings)]
$pub mod $EnumName {
#[doc(no_inline)]
pub use $EnumName as T;
super::type_level_enum! {
with_docs! {
#[doc = ::core::concat!(
"See [`", ::core::stringify!($EnumName), "`]\
[super::", ::core::stringify!($EnumName), "]"
)]
}
pub trait $EnumName : __sealed::$EnumName + ::core::marker::Sized + 'static {
const VALUE: __value::$EnumName;
}
}
mod __sealed { pub trait $EnumName {} }
mod __value {
#[derive(Debug, PartialEq, Eq)]
pub enum $EnumName { $( $Variant ),* }
}
$(
$( #[doc = $doc_variant] )*
pub enum $Variant {}
impl __sealed::$EnumName for $Variant {}
impl $EnumName for $Variant {
const VALUE: __value::$EnumName = __value::$EnumName::$Variant;
}
impl $Variant {
pub const VALUE: __value::$EnumName = __value::$EnumName::$Variant;
}
)*
}
});(
with_docs! {
$( #[doc = $doc:expr] )*
}
$item:item
) => (
$( #[doc = $doc] )*
$item
)}
use type_level_enum;