fix(napi-derive): unsound behavior while using reference and async to…

…gether

crates/backend/src/ast.rs

@@ -27,6 +27,7 @@ pub struct NapiFn {
   pub enumerable: bool,
   pub configurable: bool,
   pub catch_unwind: bool,
+  pub unsafe_: bool,
 }
 
 #[derive(Debug, Clone)]
@@ -64,7 +65,7 @@ pub enum FnKind {
   Setter,
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub enum FnSelf {
   Value,
   Ref,

crates/backend/src/codegen/fn.rs

@@ -1,9 +1,10 @@
 use proc_macro2::{Ident, Span, TokenStream};
 use quote::ToTokens;
+use syn::spanned::Spanned;
 
 use crate::{
   codegen::{get_intermediate_ident, get_register_ident, js_mod_to_token_stream},
-  BindgenResult, CallbackArg, FnKind, FnSelf, NapiFn, NapiFnArgKind, TryToTokens,
+  BindgenResult, CallbackArg, Diagnostic, FnKind, FnSelf, NapiFn, NapiFnArgKind, TryToTokens,
 };
 
 impl TryToTokens for NapiFn {
@@ -12,13 +13,78 @@ impl TryToTokens for NapiFn {
     let intermediate_ident = get_intermediate_ident(&name_str);
     let args_len = self.args.len();
 
-    let (arg_conversions, arg_names) = self.gen_arg_conversions()?;
+    let ArgConversions {
+      arg_conversions,
+      args: arg_names,
+      refs,
+      mut_ref_spans,
+      unsafe_,
+    } = self.gen_arg_conversions()?;
+    // The JS engine can't properly track mutability in an async context, so refuse to compile
+    // code that tries to use async and mutability together without `unsafe` mark.
+    if self.is_async && !mut_ref_spans.is_empty() && !unsafe_ {
+      return Diagnostic::from_vec(
+        mut_ref_spans
+          .into_iter()
+          .map(|s| Diagnostic::span_error(s, "mutable reference is unsafe with async"))
+          .collect(),
+      );
+    }
+    if Some(FnSelf::MutRef) == self.fn_self && self.is_async {
+      return Err(Diagnostic::span_error(
+        self.name.span(),
+        "&mut self is incompatible with async napi methods",
+      ));
+    }
+    let arg_ref_count = refs.len();
     let receiver = self.gen_fn_receiver();
     let receiver_ret_name = Ident::new("_ret", Span::call_site());
     let ret = self.gen_fn_return(&receiver_ret_name);
     let register = self.gen_fn_register();
     let attrs = &self.attrs;
 
+    let build_ref_container = if self.is_async {
+      quote! {
+          struct NapiRefContainer([napi::sys::napi_ref; #arg_ref_count]);
+          impl NapiRefContainer {
+            fn drop(self, env: napi::sys::napi_env) {
+              for r in self.0.into_iter() {
+                assert_eq!(
+                  unsafe { napi::sys::napi_delete_reference(env, r) },
+                  napi::sys::Status::napi_ok,
+                  "failed to delete napi ref"
+                );
+              }
+            }
+          }
+          unsafe impl Send for NapiRefContainer {}
+          unsafe impl Sync for NapiRefContainer {}
+          let _make_ref = |a: ::std::ptr::NonNull<napi::bindgen_prelude::sys::napi_value__>| {
+            let mut node_ref = ::std::mem::MaybeUninit::uninit();
+            assert_eq!(unsafe {
+                napi::bindgen_prelude::sys::napi_create_reference(env, a.as_ptr(), 1, node_ref.as_mut_ptr())
+              },
+              napi::bindgen_prelude::sys::Status::napi_ok,
+              "failed to create napi ref"
+            );
+            unsafe { node_ref.assume_init() }
+          };
+          let mut _args_array = [::std::ptr::null_mut::<napi::bindgen_prelude::sys::napi_ref__>(); #arg_ref_count];
+          let mut _arg_write_index = 0;
+
+          #(#refs)*
+
+          #[cfg(debug_assert)]
+          {
+              for a in &_args_array {
+                assert!(!a.is_null(), "failed to initialize napi ref");
+              }
+          }
+          let _args_ref = NapiRefContainer(_args_array);
+      }
+    } else {
+      quote! {}
+    };
     let native_call = if !self.is_async {
       quote! {
         napi::bindgen_prelude::within_runtime_if_available(move || {
@@ -35,16 +101,26 @@ impl TryToTokens for NapiFn {
         quote! { Ok(#receiver(#(#arg_names),*).await) }
       };
       quote! {
-        napi::bindgen_prelude::execute_tokio_future(env, async move { #call }, |env, #receiver_ret_name| {
+        napi::bindgen_prelude::execute_tokio_future(env, async move { #call }, move |env, #receiver_ret_name| {
+          _args_ref.drop(env);
           #ret
         })
       }
     };
 
+    let function_call_inner = quote! {
+      napi::bindgen_prelude::CallbackInfo::<#args_len>::new(env, cb, None).and_then(|mut cb| {
+          #build_ref_container
+          #(#arg_conversions)*
+          #native_call
+        })
+    };
+
     let function_call = if args_len == 0
       && self.fn_self.is_none()
       && self.kind != FnKind::Constructor
       && self.kind != FnKind::Factory
+      && !self.is_async
     {
       quote! { #native_call }
     } else if self.kind == FnKind::Constructor {
@@ -55,18 +131,10 @@ impl TryToTokens for NapiFn {
         if inner.load(std::sync::atomic::Ordering::Relaxed) {
           return std::ptr::null_mut();
         }
-        napi::bindgen_prelude::CallbackInfo::<#args_len>::new(env, cb, None).and_then(|mut cb| {
-          #(#arg_conversions)*
-          #native_call
-        })
+        #function_call_inner
       }
     } else {
-      quote! {
-        napi::bindgen_prelude::CallbackInfo::<#args_len>::new(env, cb, None).and_then(|mut cb| {
-          #(#arg_conversions)*
-          #native_call
-        })
-      }
+      function_call_inner
     };
 
     let function_call = if self.catch_unwind {
@@ -109,20 +177,30 @@ impl TryToTokens for NapiFn {
 }
 
 impl NapiFn {
-  fn gen_arg_conversions(&self) -> BindgenResult<(Vec<TokenStream>, Vec<TokenStream>)> {
+  fn gen_arg_conversions(&self) -> BindgenResult<ArgConversions> {
     let mut arg_conversions = vec![];
     let mut args = vec![];
+    let mut refs = vec![];
+    let mut mut_ref_spans = vec![];
+    let make_ref = |input| {
+      quote! {
+        _args_array[_arg_write_index] = _make_ref(::std::ptr::NonNull::new(#input).expect("ref ptr was null"));
+        _arg_write_index += 1;
+      }
+    };
 
     // fetch this
     if let Some(parent) = &self.parent {
       match self.fn_self {
         Some(FnSelf::Ref) => {
+          refs.push(make_ref(quote! { cb.this }));
           arg_conversions.push(quote! {
             let this_ptr = unsafe { cb.unwrap_raw::<#parent>()? };
             let this: &#parent = Box::leak(Box::from_raw(this_ptr));
           });
         }
         Some(FnSelf::MutRef) => {
+          refs.push(make_ref(quote! { cb.this }));
           arg_conversions.push(quote! {
             let this_ptr = unsafe { cb.unwrap_raw::<#parent>()? };
             let this: &mut #parent = Box::leak(Box::from_raw(this_ptr));
@@ -215,7 +293,9 @@ impl NapiFn {
                         }) = elem.as_ref()
                         {
                           if let Some(syn::PathSegment { ident, .. }) = segments.first() {
+                            refs.push(make_ref(quote! { cb.this }));
                             let token = if mutability.is_some() {
+                              mut_ref_spans.push(generic_type.span());
                               quote! { <#ident as napi::bindgen_prelude::FromNapiMutRef>::from_napi_mut_ref(env, cb.this)? }
                             } else {
                               quote! { <#ident as napi::bindgen_prelude::FromNapiRef>::from_napi_ref(env, cb.this)? }
@@ -228,15 +308,21 @@ impl NapiFn {
                       }
                     }
                   }
-                  args.push(
-                    quote! { <napi::bindgen_prelude::This as napi::NapiValue>::from_raw_unchecked(env, cb.this) },
-                  );
+                  refs.push(make_ref(quote! { cb.this }));
+                  args.push(quote! { <napi::bindgen_prelude::This as napi::NapiValue>::from_raw_unchecked(env, cb.this) });
                   skipped_arg_count += 1;
                   continue;
                 }
               }
             }
-            arg_conversions.push(self.gen_ty_arg_conversion(&ident, i, path));
+            let (arg_conversion, arg_type) = self.gen_ty_arg_conversion(&ident, i, path);
+            if NapiArgType::MutRef == arg_type {
+              mut_ref_spans.push(path.ty.span());
+            }
+            if arg_type.is_ref() {
+              refs.push(make_ref(quote! { cb.get_arg(#i) }));
+            }
+            arg_conversions.push(arg_conversion);
             args.push(quote! { #ident });
           }
         }
@@ -247,17 +333,24 @@ impl NapiFn {
       }
     }
 
-    Ok((arg_conversions, args))
+    Ok(ArgConversions {
+      arg_conversions,
+      args,
+      refs,
+      mut_ref_spans,
+      unsafe_: self.unsafe_,
+    })
   }
 
+  /// Returns a type conversion, and a boolean indicating whether this value needs to have a reference created to extend the lifetime
+  /// for async functions.
   fn gen_ty_arg_conversion(
     &self,
     arg_name: &Ident,
     index: usize,
     path: &syn::PatType,
-  ) -> TokenStream {
+  ) -> (TokenStream, NapiArgType) {
     let ty = &*path.ty;
-
     let type_check = if self.return_if_invalid {
       quote! {
         if let Ok(maybe_promise) = <#ty as napi::bindgen_prelude::ValidateNapiValue>::validate(env, cb.get_arg(#index)) {
@@ -285,28 +378,31 @@ impl NapiFn {
         elem,
         ..
       }) => {
-        quote! {
+        let q = quote! {
           let #arg_name = {
             #type_check
             <#elem as napi::bindgen_prelude::FromNapiMutRef>::from_napi_mut_ref(env, cb.get_arg(#index))?
           };
-        }
+        };
+        (q, NapiArgType::MutRef)
       }
       syn::Type::Reference(syn::TypeReference { elem, .. }) => {
-        quote! {
+        let q = quote! {
           let #arg_name = {
             #type_check
             <#elem as napi::bindgen_prelude::FromNapiRef>::from_napi_ref(env, cb.get_arg(#index))?
           };
-        }
+        };
+        (q, NapiArgType::Ref)
       }
       _ => {
-        quote! {
+        let q = quote! {
           let #arg_name = {
             #type_check
             <#ty as napi::bindgen_prelude::FromNapiValue>::from_napi_value(env, cb.get_arg(#index))?
           };
-        }
+        };
+        (q, NapiArgType::Value)
       }
     }
   }
@@ -482,3 +578,24 @@ impl NapiFn {
     }
   }
 }
+
+struct ArgConversions {
+  pub args: Vec<TokenStream>,
+  pub arg_conversions: Vec<TokenStream>,
+  pub refs: Vec<TokenStream>,
+  pub mut_ref_spans: Vec<Span>,
+  pub unsafe_: bool,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+enum NapiArgType {
+  Ref,
+  MutRef,
+  Value,
+}
+
+impl NapiArgType {
+  fn is_ref(&self) -> bool {
+    matches!(self, NapiArgType::Ref | NapiArgType::MutRef)
+  }
+}

crates/macro/src/parser/mod.rs

@@ -696,6 +696,7 @@ fn napi_fn_from_decl(
       enumerable: opts.enumerable(),
       configurable: opts.configurable(),
       catch_unwind: opts.catch_unwind().is_some(),
+      unsafe_: sig.unsafety.is_some(),
     }
   })
 }

examples/napi/__test__/typegen.spec.ts.md

@@ -247,6 +247,7 @@ Generated by [AVA](https://avajs.dev).
       name: string␊
       constructor(name: string)␊
       getCount(): number␊
+      getNameAsync(): Promise<string>␊
     }␊
     export type Blake2bHasher = Blake2BHasher␊
     /** Smoking test for type generation */␊

examples/napi/__test__/values.spec.ts

@@ -206,6 +206,11 @@ test('class', (t) => {
   })
 })
 
+test('async self in class', async (t) => {
+  const b = new Bird('foo')
+  t.is(await b.getNameAsync(), 'foo')
+})
+
 test('class factory', (t) => {
   const duck = ClassWithFactory.withName('Default')
   t.is(duck.name, 'Default')

examples/napi/index.d.ts

@@ -237,6 +237,7 @@ export class Bird {
   name: string
   constructor(name: string)
   getCount(): number
+  getNameAsync(): Promise<string>
 }
 export type Blake2bHasher = Blake2BHasher
 /** Smoking test for type generation */

examples/napi/src/class.rs

@@ -123,6 +123,12 @@ impl Bird {
   pub fn get_count(&self) -> u32 {
     1234
   }
+
+  #[napi]
+  pub async fn get_name_async(&self) -> &str {
+    tokio::time::sleep(std::time::Duration::new(1, 0)).await;
+    self.name.as_str()
+  }
 }
 
 /// Smoking test for type generation