feat: add wit-bindgen-sample container

__wasm/wit-bindgen-sample/container/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "container"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = "1.0.58"
+wasmtime = "0.38.1"
+wit-bindgen-wasmtime = { path = '../wit-bindgen/crates/wasmtime' }

__wasm/wit-bindgen-sample/container/src/main.rs

@@ -0,0 +1,72 @@
+use anyhow::Result;
+use wasmtime::{Config, Engine, Instance, Linker, Module, Store};
+
+use container::*;
+
+wit_bindgen_wasmtime::export!("../container.wit");
+
+#[derive(Default)]
+pub struct MyContainer;
+
+impl Container for MyContainer {
+    fn fetch(&mut self, s: &str) -> String {
+        format!("FETCHED: {}", s)
+    }
+}
+
+wit_bindgen_wasmtime::import!("../exports.wit");
+
+
+fn main() -> Result<()> {
+    use exports::*;
+    let wasm = "../engine/target/wasm32-unknown-unknown/debug/engine.wasm";
+    let (exports, mut store) = instantiate(
+        wasm,
+        |linker| container::add_to_linker(linker, |cx| -> &mut MyContainer { &mut cx.imports }),
+        |store, module, linker| Exports::instantiate(store, module, linker, |cx| &mut cx.exports),
+    )?;
+    let a = exports.eval_javascript(&mut store, "[script]");
+
+    println!("Hello, world! {:?}", a);
+
+    Ok(())
+}
+
+struct Context<I, E> {
+    imports: I,
+    exports: E,
+}
+
+fn instantiate<I: Default, E: Default, T>(
+    wasm: &str,
+    add_imports: impl FnOnce(&mut Linker<Context<I, E>>) -> Result<()>,
+    mk_exports: impl FnOnce(
+        &mut Store<Context<I, E>>,
+        &Module,
+        &mut Linker<Context<I, E>>,
+    ) -> Result<(T, Instance)>,
+) -> Result<(T, Store<Context<I, E>>)> {
+    let engine = Engine::new(&default_config()?)?;
+    let module = Module::from_file(&engine, wasm)?;
+
+    let mut linker = Linker::new(&engine);
+    add_imports(&mut linker)?;
+
+    let mut store = Store::new(
+        &engine,
+        Context {
+            imports: I::default(),
+            exports: E::default(),
+        },
+    );
+    let (exports, _instance) = mk_exports(&mut store, &module, &mut linker)?;
+    Ok((exports, store))
+}
+
+fn default_config() -> Result<Config> {
+    // Create an engine with caching enabled to assist with iteration in this project.
+    let mut config = Config::new();
+    config.cache_config_load_default()?;
+    config.wasm_backtrace_details(wasmtime::WasmBacktraceDetails::Enable);
+    Ok(config)
+}