JS API improvement

lib/api/src/js/export.rs

@@ -118,6 +118,7 @@ pub enum Export {
 }
 
 impl Export {
+    /// Return the export as a `JSValue`.
     pub fn as_jsvalue(&self) -> &JsValue {
         match self {
             Export::Memory(js_wasm_memory) => js_wasm_memory.memory.as_ref(),

lib/api/src/js/instance.rs

@@ -100,7 +100,7 @@ impl Instance {
             .instantiate(resolver)
             .map_err(|e| InstantiationError::Start(e))?;
 
-        let self_instance = Self::from_module_and_instance(module, instance);
+        let self_instance = Self::from_module_and_instance(module, instance)?;
         self_instance.init_envs(&imports)?;
         Ok(self_instance)
     }
@@ -112,29 +112,40 @@ impl Instance {
     /// Is expected that the function [`Instance::init_envs`] is run manually
     /// by the user in case the instance has any Wasmer imports, so the function
     /// environments are properly initiated.
-    pub fn from_module_and_instance(module: &Module, instance: WebAssembly::Instance) -> Self {
+    #[doc(hidden)]
+    pub fn from_module_and_instance(
+        module: &Module,
+        instance: WebAssembly::Instance,
+    ) -> Result<Self, InstantiationError> {
         let store = module.store();
         let instance_exports = instance.exports();
         let exports = module
             .exports()
             .map(|export_type| {
                 let name = export_type.name();
                 let extern_type = export_type.ty().clone();
-                let js_export = js_sys::Reflect::get(&instance_exports, &name.into()).unwrap();
+                let js_export =
+                    js_sys::Reflect::get(&instance_exports, &name.into()).map_err(|_e| {
+                        InstantiationError::Link(format!(
+                            "Can't get {} from the instance exports",
+                            &name
+                        ))
+                    })?;
                 let export: Export = (js_export, extern_type).into();
                 let extern_ = Extern::from_vm_export(store, export);
-                (name.to_string(), extern_)
+                Ok((name.to_string(), extern_))
             })
-            .collect::<Exports>();
+            .collect::<Result<Exports, InstantiationError>>()?;
 
-        Self {
+        Ok(Self {
             instance,
             module: module.clone(),
             exports,
-        }
+        })
     }
 
     /// Initialize the given extern imports with the Instance
+    #[doc(hidden)]
     pub fn init_envs(&self, imports: &[Export]) -> Result<(), InstantiationError> {
         for import in imports {
             if let Export::Function(func) = import {

lib/api/src/js/js_import_object.rs

@@ -0,0 +1,71 @@
+use crate::js::{Export, ExternType, Module, NamedResolver};
+use std::collections::HashMap;
+
+/// This struct is used in case you want to create an `Instance`
+/// of a `Module` with imports that are provided directly from
+/// Javascript with a JS Object.
+#[derive(Clone, Default)]
+pub struct JsImportObject {
+    module_imports: HashMap<(String, String), ExternType>,
+    object: js_sys::Object,
+}
+
+unsafe impl Send for JsImportObject {}
+unsafe impl Sync for JsImportObject {}
+
+impl JsImportObject {
+    /// Create a new `JsImportObject`.
+    ///
+    /// # Usage
+    /// ```ignore
+    /// # use wasmer::JsImportObject;
+    /// let import_object = JsImportObject::new(&module, js_object);
+    /// ```
+    pub fn new(module: &Module, object: js_sys::Object) -> Self {
+        let module_imports = module
+            .imports()
+            .map(|import| {
+                (
+                    (import.module().to_string(), import.name().to_string()),
+                    import.ty().clone(),
+                )
+            })
+            .collect::<HashMap<(String, String), ExternType>>();
+        Self {
+            module_imports,
+            object,
+        }
+    }
+
+    /// Gets an export given a module and a name
+    ///
+    /// # Usage
+    /// ```ignore
+    /// # use wasmer::JsImportObject;
+    /// let import_object = JsImportObject::new(&module, js_object);
+    /// import_object.get_export("module", "name");
+    /// ```
+    pub fn get_export(&self, module: &str, name: &str) -> Option<Export> {
+        let namespace = js_sys::Reflect::get(&self.object, &name.into()).ok()?;
+        let js_export = js_sys::Reflect::get(&namespace, &name.into()).ok()?;
+        match self
+            .module_imports
+            .get(&(module.to_string(), name.to_string()))
+        {
+            Some(extern_type) => Some((js_export, extern_type.clone()).into()),
+            None => None,
+        }
+    }
+}
+
+impl Into<js_sys::Object> for JsImportObject {
+    fn into(self) -> js_sys::Object {
+        self.object
+    }
+}
+
+impl NamedResolver for JsImportObject {
+    fn resolve_by_name(&self, module: &str, name: &str) -> Option<Export> {
+        self.get_export(module, name)
+    }
+}

lib/api/src/js/mod.rs

@@ -31,6 +31,7 @@ mod exports;
 mod externals;
 mod import_object;
 mod instance;
+mod js_import_object;
 mod module;
 #[cfg(feature = "wasm-types-polyfill")]
 mod module_info_polyfill;
@@ -50,13 +51,15 @@ pub use wasmer_derive::WasmerEnv;
 
 pub use crate::js::cell::WasmCell;
 pub use crate::js::env::{HostEnvInitError, LazyInit, WasmerEnv};
+pub use crate::js::export::Export;
 pub use crate::js::exports::{ExportError, Exportable, Exports, ExportsIterator};
 pub use crate::js::externals::{
     Extern, FromToNativeWasmType, Function, Global, HostFunction, Memory, MemoryError, Table,
     WasmTypeList,
 };
 pub use crate::js::import_object::{ImportObject, ImportObjectIterator, LikeNamespace};
 pub use crate::js::instance::{Instance, InstantiationError};
+pub use crate::js::js_import_object::JsImportObject;
 pub use crate::js::module::{Module, ModuleTypeHints};
 pub use crate::js::native::NativeFunc;
 pub use crate::js::ptr::{Array, Item, WasmPtr};