test(api) Test that exports work after the instance has been freed.

lib/api/tests/instance.rs

@@ -0,0 +1,39 @@
+use anyhow::Result;
+use wasmer::*;
+
+#[test]
+fn exports_work_after_multiple_instances_have_been_freed() -> Result<()> {
+    let store = Store::default();
+    let module = Module::new(
+        &store,
+        "
+    (module
+      (type $sum_t (func (param i32 i32) (result i32)))
+      (func $sum_f (type $sum_t) (param $x i32) (param $y i32) (result i32)
+        local.get $x
+        local.get $y
+        i32.add)
+      (export \"sum\" (func $sum_f)))
+",
+    )?;
+
+    let import_object = ImportObject::new();
+    let instance = Instance::new(&module, &import_object)?;
+    let instance2 = instance.clone();
+    let instance3 = instance.clone();
+
+    // The function is cloned to “break” the connection with `instance`.
+    let sum = instance.exports.get_function("sum")?.clone();
+
+    drop(instance);
+    drop(instance2);
+    drop(instance3);
+
+    // All instances have been dropped, but `sum` continues to work!
+    assert_eq!(
+        sum.call(&[Value::I32(1), Value::I32(2)])?.into_vec(),
+        vec![Value::I32(3)],
+    );
+
+    Ok(())
+}