lib/web_ui/dev/test_dart2wasm.js

// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// This script runs in HTML files and loads and instantiates dart unit tests
// that are compiled to WebAssembly. It is based off of the `test/dart.js`
// script from the `test` dart package.

window.onload = async function () {
  // Sends an error message to the server indicating that the script failed to
  // load.
  //
  // This mimics a MultiChannel-formatted message.
  var sendLoadException = function (message) {
    window.parent.postMessage({
      "href": window.location.href,
      "data": [0, { "type": "loadException", "message": message }],
      "exception": true,
    }, window.location.origin);
  }

  // Listen for dartLoadException events and forward to the server.
  window.addEventListener('dartLoadException', function (e) {
    sendLoadException(e.detail);
  });

  // The basename of the current page.
  var name = window.location.href.replace(/.*\//, '').replace(/#.*/, '');

  // Find <link rel="x-dart-test">.
  var links = document.getElementsByTagName("link");
  var testLinks = [];
  var length = links.length;
  for (var i = 0; i < length; ++i) {
    if (links[i].rel == "x-dart-test") testLinks.push(links[i]);
  }

  if (testLinks.length != 1) {
    sendLoadException(
      'Expected exactly 1 <link rel="x-dart-test"> in ' + name + ', found ' +
      testLinks.length + '.');
    return;
  }

  var link = testLinks[0];

  if (link.href == '') {
    sendLoadException(
      'Expected <link rel="x-dart-test"> in ' + name + ' to have an "href" ' +
      'attribute.');
    return;
  }

  let dart2wasm_runtime;
  let moduleInstance;
  try {
    const isSkwasm = link.hasAttribute('skwasm');
    const imports = isSkwasm ? new Promise((resolve) => {
      const skwasmScript = document.createElement('script');
      skwasmScript.src = '/canvaskit/skwasm.js';

      document.body.appendChild(skwasmScript);
      skwasmScript.addEventListener('load', async () => {
        const skwasmInstance = await skwasm();
        window._flutter_skwasmInstance = skwasmInstance;
        resolve({
          "skwasm": skwasmInstance.wasmExports,
          "skwasmWrapper": skwasmInstance,
          "ffi": {
            "memory": skwasmInstance.wasmMemory,
          }
        });
      });
    }) : {};

    let baseName = link.href + '.browser_test.dart';
    dart2wasm_runtime = await import(baseName + '.mjs');
    const dartModulePromise = WebAssembly.compileStreaming(fetch(baseName + '.wasm'));
    moduleInstance = await dart2wasm_runtime.instantiate(dartModulePromise, imports);
  } catch (exception) {
    const message = `Failed to fetch and instantiate wasm module: ${exception}`;
    sendLoadException(message);
  }

  if (moduleInstance) {
    try {
      await dart2wasm_runtime.invoke(moduleInstance);
    } catch (exception) {
      const message = `Exception while invoking test: ${exception}`;
      sendLoadException(message);
    }
  }
};