it("Sub-context work", async () => {
    const c = new Context(store);

    let subRef: Context;
    let canAbort = false;
    c.withSub(async sub => {
      subRef = sub;
      await sub.withStopper({
        stop: async () => {
          if (!canAbort) {
            throw new Error("can't abort");
          }
        },
        work: async () => {
          await new ItchPromise(() => {
            /* muffin */
          });
        },
      });
    }).catch(() => {
      // woops
    });

    await assert.isRejected(c.tryAbort());
    canAbort = true;
    await c.tryAbort();
    await assert.isTrue(c.isDead());
    await assert.isTrue(subRef.isDead());
  });

export async function performLaunch(
  ctx: Context,
  logger: RecordingLogger,
  cave: Cave,
  game: Game
) {
  ctx.emitProgress({ progress: -1, stage: "configure" });

  const { store } = ctx;
  const taskId = ctx.getTaskId();
  store.dispatch(
    actions.taskProgress({
      id: taskId,
      progress: -1,
      stage: "prepare",
    })
  );

  // TODO: have butler check morphing and queue a heal if needed
  const { appVersion } = store.getState().system;
  logger.info(`itch ${appVersion} launching '${game.title}' (#${game.id})`);

  const { preferences } = store.getState();
  const prereqsDir = paths.prereqsPath();

  // TODO: extract that to another module
  let prereqsModal: TypedModal<any, any>;
  let prereqsStateParams: PrereqsStateParams;

  function closePrereqsModal() {
    if (!prereqsModal) {
      return;
    }

    store.dispatch(
      actions.closeModal({
        wind: "root",
        id: prereqsModal.id,
      })
    );
    prereqsModal = null;
  }

  let powerSaveBlockerId: number = null;

  let cancelled = false;
  let launchConvo: Conversation;
  await ctx.withStopper({
    work: async () => {
      try {
        await mcall(
          messages.Launch,
          {
            caveId: cave.id,
            prereqsDir,
            sandbox: preferences.isolateApps,
          },
          convo => {
            launchConvo = convo;
            hookLogging(convo, logger);

            convo.on(messages.PickManifestAction, async ({ actions }) => {
              const index = await pickManifestAction(store, actions, game);
              return { index };
            });

            convo.on(messages.AcceptLicense, async ({ text }) => {
              const res = await promisedModal(
                store,
                modals.naked.make({
                  wind: "root",
                  title: ["prompt.sla.title"],
                  message: ["prompt.sla.message"],
                  detail: text,
                  widgetParams: {} as any,
                  buttons: [
                    {
                      label: ["prompt.sla.accept"],
                      action: actions.modalResponse({}),
                    },
                    "cancel",
                  ],
                })
              );

              if (res) {
                return { accept: true };
              }
              return { accept: false };
            });

            convo.on(messages.HTMLLaunch, async params => {
              return await performHTMLLaunch({
                ctx,
                logger,
                game,
                params,
              });
            });

//.........这里部分代码省略.........

async function asTask(opts: AsTaskOpts) {
  const id = uuid();

  const { store, name, gameId, caveId } = opts;

  const logger = recordingLogger(mainLogger);

  store.dispatch(
    actions.taskStarted({
      id,
      name,
      gameId,
      caveId,
      startedAt: Date.now(),
    })
  );

  const ctx = new Context(store);
  ctx.registerTaskId(id);
  ctx.on("progress", (ev: ProgressInfo) => {
    store.dispatch(actions.taskProgress({ id, ...ev }));
  });

  getCurrentTasks()[id] = ctx;

  let err: Error;

  const { work, onError, onCancel } = opts;

  try {
    await work(ctx, logger);
  } catch (e) {
    err = e;
  }

  delete getCurrentTasks()[id];

  if (err) {
    if (isCancelled(err)) {
      mainLogger.warn(`Task ${name} cancelled`);
      if (onCancel) {
        await onCancel();
      }
    } else if (isAborted(err)) {
      mainLogger.warn(`Task ${name} aborted`);
      if (onCancel) {
        await onCancel();
      }
    } else {
      mainLogger.warn(`Task ${name} threw: ${err.stack}`);
      if (onError) {
        await onError(err, logger.getLog());
      }
    }
  }

  store.dispatch(
    actions.taskEnded({
      id,
      err: err ? `${err}` : null,
    })
  );
}

            convo.on(messages.PrereqsStarted, async ({ tasks }) => {
              prereqsStateParams = {
                gameTitle: game.title,
                tasks: {},
              };

              for (const name of Object.keys(tasks)) {
                const task = tasks[name];
                prereqsStateParams.tasks[name] = {
                  fullName: task.fullName,
                  order: task.order,
                  status: PrereqStatus.Pending,
                  progress: 0,
                  eta: 0,
                  bps: 0,
                };
              }

              prereqsModal = modals.prereqsState.make({
                wind: "root",
                title: ["grid.item.installing"],
                message: "",
                widgetParams: prereqsStateParams,
                buttons: [
                  {
                    id: "modal-cancel",
                    label: ["prompt.action.cancel"],
                    action: actions.abortTask({ id: ctx.getTaskId() }),
                    className: "secondary",
                  },
                ],
                unclosable: true,
              });
              store.dispatch(actions.openModal(prereqsModal));
            });

 const ret = await (async () => {
   return c.withStopper({
     stop: async () => null,
     work: async () => 42,
   });
 })();