patch-wechat-webassembly.js

/**
 * WebAssembly has changed to WXWebAssembly after WeChat 8.0
 * 0. not simd or thread support.
 * 1. only load local wasm file is allowed.
 * 2. WebAssembly.validate not working so env registerFlag doesn't work
 * @see https://developers.weixin.qq.com/community/develop/doc/000e2c019f8a003d5dfbb54c251c00?jumpto=comment&commentid=000eac66934960576d0cb1a7256c
 */
 export function patchWechatWebAssembly() {
  return {
    transform(code, file) {
      // remove node imports
      if (
        file.endsWith('tfjs-backend-wasm-threaded-simd.worker.js') ||
        file.endsWith('tfjs-backend-wasm-threaded-simd.js')
      ) {
        code = code.replace(`require("worker_threads")`, 'null')
        code = code.replace(`require("perf_hooks")`, 'null')
      }

      // it is not a nice way, but WebAssembly.validate not working and SIMD is not support in WXWebAssembly
      if (file.endsWith('backend_wasm.ts')) {
        code = code.replace(`env().getAsync('WASM_HAS_SIMD_SUPPORT')`, 'false')
        code = code.replace(`env().getAsync('WASM_HAS_MULTITHREAD_SUPPORT')`, 'false')
        code = code.replace(
          `function createInstantiateWasmFunc(path) {`,
          `function createInstantiateWasmFunc(path) {
  return function (imports, callback) {
    WebAssembly.instantiate(path, imports).then(function (output) {
        callback(output.instance, output.module);
    });
    return {};
  }`)
      }

      code = code.replace(`WebAssembly.`, `WXWebAssembly.`)
      code = code.replace(`typeof WebAssembly`, `typeof WXWebAssembly`)
      return { code };
    }
  }
}