wasm import: remove double compilation

[kevinkassimo]

Follow-up for #3328

wasm import currently does double compilation: the first compilation happens here:

deno/cli/js/compiler.ts

Line 753 in 4902a1c

const compiled = await WebAssembly.compile(buffer);

and the second time happens here:

deno/cli/compilers/wasm_wrap.js

Line 15 in 4902a1c

const compiled = await WebAssembly.compile(buffer);

The first compilation is to enable us to get imports/exports info such that we are able to build a dynamic script with static imports and named exports. The second one is for the later actual instantiation.

Ideally we should be able to just compile once, and in the module evaluation script we can somehow get a handle to the old compiled object. However currently these 2 compilations happens in 2 different isolates (first in some compiler isolate, second in the main isolate), thus making storing and transferring the compiled object difficult.

I'm not so sure if SyntheticModule APIs could be useful, since handling imports in its evaluation steps would be painful while doing exports is easy. Also we still need to create some js/.d.ts code for the module to placate TS compiler for named exports (especially under de-structuring)

[kevinkassimo]

For clarification, this is a generated JS wrapper script for wasm imports (with cli/tests/051_wasm_import/simple.wasm):

const importObject = Object.create(null);
/* BEGIN static import inject */
import * as m0 from "./wasm-dep.js";
importObject["./wasm-dep.js"] = m0;
import * as m1 from "http://127.0.0.1:4545/cli/tests/051_wasm_import/remote.ts";
importObject["http://127.0.0.1:4545/cli/tests/051_wasm_import/remote.ts"] = m1;
/* END static import inject */

function base64ToUint8Array(data) {
  const binString = window.atob(data);
  const size = binString.length;
  const bytes = new Uint8Array(size);
  for (let i = 0; i < size; i++) {
    bytes[i] = binString.charCodeAt(i);
  }
  return bytes;
}

const buffer = base64ToUint8Array("AGFzbQEAAAABEwRgAAF/YAAAYAJ/fwF/YAF/AX8CdgMNLi93YXNtLWRlcC5qcwRqc0ZuAAANLi93YXNtLWRlcC5qcwhqc0luaXRGbgABOWh0dHA6Ly8xMjcuMC4wLjE6NDU0NS9jbGkvdGVzdHMvMDUxX3dhc21faW1wb3J0L3JlbW90ZS50cwpqc1JlbW90ZUZuAAADBQQBAgMDByEDA2FkZAAEC2FkZEltcG9ydGVkAAUJYWRkUmVtb3RlAAYIAQMKHgQEABABCwcAIAAgAWoLBwAgABAAagsHACAAEAJqCw==");
const compiled = await WebAssembly.compile(buffer);

const instance = new WebAssembly.Instance(compiled, importObject);

/* BEGIN named exports inject */
export const add = instance.exports.add;
export const addImported = instance.exports.addImported;
export const addRemote = instance.exports.addRemote;
/* END named exports inject */

[SyrupThinker]

This can probably be closed with the removal of wasm imports in 2b66b8a.

[bartlomieju]

Closing in favor of #5609