const { PromiseUtils } = ChromeUtils.import(
  "resource://gre/modules/PromiseUtils.jsm"
);

let dir = getChromeDir(getResolvedURI(gTestPath));
dir.append("file_dummy.html");
const uriString = Services.io.newFileURI(dir).spec;

add_task(async function() {
  await BrowserTestUtils.withNewTab("https://example.com", async function(
    browser
  ) {
    // Override the browser's `prepareToChangeRemoteness` so that we can delay
    // the process switch for an indefinite amount of time. This will allow us
    // to control the timing of the resolve call to trigger the bug.
    let prepareToChangeCalled = PromiseUtils.defer();
    let finishSwitch = PromiseUtils.defer();
    let oldPrepare = browser.prepareToChangeRemoteness;
    browser.prepareToChangeRemoteness = async () => {
      prepareToChangeCalled.resolve();
      await oldPrepare.call(browser);
      await finishSwitch.promise;
    };

    // Begin a process switch, which should cause `prepareToChangeRemoteness` to
    // be called. We do this from the content process to make sure the frontend
    // has no chance to trigger an eager process switch.
    info("Beginning process switch into file URI process");
    let browserLoaded = BrowserTestUtils.browserLoaded(browser);
    await SpecialPowers.spawn(browser, [uriString], uri => {
      content.location = uri;
    });
    await prepareToChangeCalled.promise;

    // The tab we opened is now midway through process switching. Open another
    // browser within the same tab, and immediately close it after the load
    // finishes.
    info("Creating new tab loaded in file URI process");
    let fileProcess;
    let browserParentDestroyed = PromiseUtils.defer();
    await BrowserTestUtils.withNewTab(uriString, async function(otherBrowser) {
      let remoteTab = otherBrowser.frameLoader.remoteTab;
      fileProcess = remoteTab.contentProcessId;
      info("Loaded test URI in pid: " + fileProcess);

      browserParentDestroyed.resolve(
        TestUtils.topicObserved(
          "ipc:browser-destroyed",
          subject => subject === remoteTab
        )
      );
    });
    await browserParentDestroyed.promise;

    // This browser has now been closed, which could cause the file content
    // process to begin shutting down, despite us process switching into it.
    // We can now allow the process switch to finish, and wait for the load to
    // finish as well.
    info("BrowserParent has been destroyed, finishing process switch");
    finishSwitch.resolve();
    await browserLoaded;

    info("Load complete");
    is(
      browser.frameLoader.remoteTab.contentProcessId,
      fileProcess,
      "Should have loaded in the same file URI process"
    );
  });
});