Merge #2569

2569: refactor(api): add Send + Sync trait when creating an instance r=Amanieu a=bnjjj

# Description

I'm currently implementing wasmer inside Krustlet (krustlet/krustlet#677). Then I had to force the thread safety of trait object used to create a wasmer instance. I know it could be a breaking change and maybe I miss some backgrounds about this. So feel free to let me know what do you think and how we could have a better implementation if needed. I'm open to any suggestions.


Co-authored-by: Benjamin Coenen <5719034+bnjjj@users.noreply.github.com>

lib/api/src/sys/import_object.rs

@@ -41,7 +41,7 @@ pub trait LikeNamespace {
 /// ```
 #[derive(Clone, Default)]
 pub struct ImportObject {
-    map: Arc<Mutex<HashMap<String, Box<dyn LikeNamespace>>>>,
+    map: Arc<Mutex<HashMap<String, Box<dyn LikeNamespace + Send + Sync>>>>,
 }
 
 impl ImportObject {
@@ -87,7 +87,7 @@ impl ImportObject {
     pub fn register<S, N>(&mut self, name: S, namespace: N) -> Option<Box<dyn LikeNamespace>>
     where
         S: Into<String>,
-        N: LikeNamespace + 'static,
+        N: LikeNamespace + Send + Sync + 'static,
     {
         let mut guard = self.map.lock().unwrap();
         let map = guard.borrow_mut();

lib/api/src/sys/instance.rs

@@ -112,7 +112,10 @@ impl Instance {
     /// Those are, as defined by the spec:
     ///  * Link errors that happen when plugging the imports into the instance
     ///  * Runtime errors that happen when running the module `start` function.
-    pub fn new(module: &Module, resolver: &dyn Resolver) -> Result<Self, InstantiationError> {
+    pub fn new(
+        module: &Module,
+        resolver: &(dyn Resolver + Send + Sync),
+    ) -> Result<Self, InstantiationError> {
         let store = module.store();
         let handle = module.instantiate(resolver)?;
         let exports = module

lib/engine/src/resolver.rs

@@ -64,7 +64,7 @@ impl<T: NamedResolver> NamedResolver for &T {
     }
 }
 
-impl NamedResolver for Box<dyn NamedResolver> {
+impl NamedResolver for Box<dyn NamedResolver + Send + Sync> {
     fn resolve_by_name(&self, module: &str, field: &str) -> Option<Export> {
         (**self).resolve_by_name(module, field)
     }
@@ -293,7 +293,7 @@ pub fn resolve_imports(
 }
 
 /// A [`Resolver`] that links two resolvers together in a chain.
-pub struct NamedResolverChain<A: NamedResolver, B: NamedResolver> {
+pub struct NamedResolverChain<A: NamedResolver + Send + Sync, B: NamedResolver + Send + Sync> {
     a: A,
     b: B,
 }
@@ -303,31 +303,31 @@ pub struct NamedResolverChain<A: NamedResolver, B: NamedResolver> {
 /// ```
 /// # use wasmer_engine::{ChainableNamedResolver, NamedResolver};
 /// # fn chainable_test<A, B>(imports1: A, imports2: B)
-/// # where A: NamedResolver + Sized,
-/// #       B: NamedResolver + Sized,
+/// # where A: NamedResolver + Sized + Send + Sync,
+/// #       B: NamedResolver + Sized + Send + Sync,
 /// # {
 /// // override duplicates with imports from `imports2`
 /// imports1.chain_front(imports2);
 /// # }
 /// ```
-pub trait ChainableNamedResolver: NamedResolver + Sized {
+pub trait ChainableNamedResolver: NamedResolver + Sized + Send + Sync {
     /// Chain a resolver in front of the current resolver.
     ///
     /// This will cause the second resolver to override the first.
     ///
     /// ```
     /// # use wasmer_engine::{ChainableNamedResolver, NamedResolver};
     /// # fn chainable_test<A, B>(imports1: A, imports2: B)
-    /// # where A: NamedResolver + Sized,
-    /// #       B: NamedResolver + Sized,
+    /// # where A: NamedResolver + Sized + Send + Sync,
+    /// #       B: NamedResolver + Sized + Send + Sync,
     /// # {
     /// // override duplicates with imports from `imports2`
     /// imports1.chain_front(imports2);
     /// # }
     /// ```
     fn chain_front<U>(self, other: U) -> NamedResolverChain<U, Self>
     where
-        U: NamedResolver,
+        U: NamedResolver + Send + Sync,
     {
         NamedResolverChain { a: other, b: self }
     }
@@ -339,28 +339,28 @@ pub trait ChainableNamedResolver: NamedResolver + Sized {
     /// ```
     /// # use wasmer_engine::{ChainableNamedResolver, NamedResolver};
     /// # fn chainable_test<A, B>(imports1: A, imports2: B)
-    /// # where A: NamedResolver + Sized,
-    /// #       B: NamedResolver + Sized,
+    /// # where A: NamedResolver + Sized + Send + Sync,
+    /// #       B: NamedResolver + Sized + Send + Sync,
     /// # {
     /// // override duplicates with imports from `imports1`
     /// imports1.chain_back(imports2);
     /// # }
     /// ```
     fn chain_back<U>(self, other: U) -> NamedResolverChain<Self, U>
     where
-        U: NamedResolver,
+        U: NamedResolver + Send + Sync,
     {
         NamedResolverChain { a: self, b: other }
     }
 }
 
 // We give these chain methods to all types implementing NamedResolver
-impl<T: NamedResolver> ChainableNamedResolver for T {}
+impl<T: NamedResolver + Send + Sync> ChainableNamedResolver for T {}
 
 impl<A, B> NamedResolver for NamedResolverChain<A, B>
 where
-    A: NamedResolver,
-    B: NamedResolver,
+    A: NamedResolver + Send + Sync,
+    B: NamedResolver + Send + Sync,
 {
     fn resolve_by_name(&self, module: &str, field: &str) -> Option<Export> {
         self.a
@@ -371,8 +371,8 @@ where
 
 impl<A, B> Clone for NamedResolverChain<A, B>
 where
-    A: NamedResolver + Clone,
-    B: NamedResolver + Clone,
+    A: NamedResolver + Clone + Send + Sync,
+    B: NamedResolver + Clone + Send + Sync,
 {
     fn clone(&self) -> Self {
         Self {

lib/wasi/src/lib.rs

@@ -109,11 +109,12 @@ impl WasiEnv {
     pub fn import_object_for_all_wasi_versions(
         &mut self,
         module: &Module,
-    ) -> Result<Box<dyn NamedResolver>, WasiError> {
+    ) -> Result<Box<dyn NamedResolver + Send + Sync>, WasiError> {
         let wasi_versions =
             get_wasi_versions(module, false).ok_or(WasiError::UnknownWasiVersion)?;
 
-        let mut resolver: Box<dyn NamedResolver> = { Box::new(()) };
+        let mut resolver: Box<dyn NamedResolver + Send + Sync> =
+            { Box::new(()) as Box<dyn NamedResolver + Send + Sync> };
         for version in wasi_versions.iter() {
             let new_import_object =
                 generate_import_object_from_env(module.store(), self.clone(), *version);