task-in-sdk.js

const { Task } = Cu.import("resource://gre/modules/Task.jsm", {});
const { defer, all } = require("sdk/core/promise");
const { setTimeout } = require("sdk/timers");

Task.spawn(function * () {
    let item1 = yield getItem(1);
    let [item2, item3] = all([getItem(2), getItem(3)]);
    console.log(item1, item2, item3); // 1, 2, 3
}).then(function () {
    console.log('all items processed')
});

function getItem(val) {
    let {
        deferred, resolve
    } = defer();
    setTimeout(() => resolve(val));
    return deferred;
}

The code above will print undefined but in the correct blocking order (we want the task block until all values returned).

"before" main.js:7
undefined undefined undefined main.js:50
"final" main.js:63
"all items processed"

The code below will print. Order is not right but at least we can get the values back.

"before" main.js:7
"final" main.js:43
1 2 3 main.js:24
"all items processed"

const { Cu} = require("chrome");
const { Task } = Cu.import("resource://gre/modules/Task.jsm", {});
const { defer, all } = require("sdk/core/promise");
const { setTimeout } = require("sdk/timers");
const { search } = require("sdk/places/history");

console.log("before");

Task.spawn(function * () {
    let item1 = yield getItem(1);
    let item23 = yield all([getItem(2), getItem(3)]);
    console.log(item1, item23[0], item23[1]);   // print 1,2,3

    //let [item2, item3] = all([getItem(2), getItem(3)]);
    //console.log(item1, item2, item3); // 1, 2, 3

}).then(function () {
    console.log('all items processed')
});

function getItem(val) {
/*    let {
        deferred, resolve
    } = defer();
*/
    var deferred = defer();
    setTimeout(() => deferred.resolve(val));
    return deferred.promise;
}

console.log("final");



/*
Task.spawn(function *() {
    let spromise = search({query: "mozilla"});
    yield spromise;
    return spromise;
}).then(function (result) {
    console.log(result.on("end", function (r) { console.log(r); }));
});
*/