module imports cannot synchronously access exports if it autostarts #969

When using the JS API to dynamically link imports to a wasm module, if that module has an autostart e.g. (start $main) then those imports cannot synchronously access any of the modules exports. Basically you can't have synchronous cyclic dependencies.

There are workarounds:

• Don't autostart
• Have wasm module import everything that is cyclic (depending on what it is, e.g. import the table) instead of it creating and exporting it

const instance = new WebAssembly.Instance(module, {
  env: {
    callIndirect: index => {
      // throws here, instance is not defined yet
      // as the `new WebAssembly.Instance` has not
      // yet returned
      instance.exports.table.get(index)();
    }
  }
});

(module
  (func $callIndirect (import "env" "callIndirect") (param i32))
  (func $main
    i32.const 0
    call $callIndirect
  )
  (func $callback)
  (memory 1)
  (table $table anyfunc (elem $callback))
  (export "table" (table $table))
  (start $main)
)

Demo: example.zip