Crappy examples for <https://github.com/novemberborn/legendary/tree/cancellation-c>

cancellation-c.js

var legendary = require("legendary");

test1();
test2();
test3();
test4();
test5();
test6();
test7();

function test1(){
  // Create a pending promise p1
  var p1 = new legendary.Promise(function(resolve){
    setTimeout(resolve, 2000, "test1");
  });

  p1.then(function(value){
    console.log("1.1:", value);
  }, function(reason){
    console.log("1.1:", reason, reason.stack);
    throw reason;
  });

  var p2 = p1.then(null, function(reason){
    console.log("1.2:", reason, reason.stack);
    throw reason;
  });
  p2.then(null, function(reason){
    console.log("1.3:", reason, reason.stack);
  });

  // Cancelling p1 means that all derived promises get cancelled too.
  p1.cancel();
}

function test2(){
  // Create a pending promise p1
  var p1 = new legendary.Promise(function(resolve){
    setTimeout(resolve, 2000, "test2");
  });

  p1.then(function(value){
    console.log("2.1:", value);
  }, function(reason){
    console.log("2.1:", reason, reason.stack);
    throw reason;
  });
  var p2 = p1.then(null, function(reason){
    console.log("2.2:", reason, reason.stack);
    throw reason;
  });
  p2.then(null, function(reason){
    console.log("2.3:", reason, reason.stack);
  });

  // Cancelling p2 propagates to p1, which means that all promises derived
  // from p1 get cancelled.
  p2.cancel();
}

function test3(){
  // Create a rejected promise p1
  var p1 = new legendary.Promise(function(){
    throw new Error("Resolver threw");
  });

  p1.then(function(value){
    console.log("3.1:", value);
  }, function(reason){
    console.log("3.1:", reason, reason.stack);
    throw reason;
  });
  var p2 = p1.then(null, function(reason){
    console.log("3.2:", reason, reason.stack);
    throw reason;
  });
  p2.then(null, function(reason){
    console.log("3.3:", reason, reason.stack);
  });

  // p1 is already rejected, so cancellation is a no-op.
  p1.cancel();
}

function test4(){
  // Create a rejected promise p1
  var p1 = new legendary.Promise(function(){
    throw new Error("Resolver threw");
  });

  p1.then(function(value){
    console.log("4.1:", value);
  }, function(reason){
    console.log("4.1:", reason, reason.stack);
    throw reason;
  });

  // Even though p1 is rejected, p2 is pending because the callbacks don't
  // execute until a next turn.
  var p2 = p1.then(null, function(reason){
    console.log("4.2:", reason, reason.stack);
    throw reason;
  });
  p2.then(null, function(reason){
    console.log("4.3:", reason, reason.stack);
  });

  // Cancelling p2 only cancels 4.2 and 4.3, but not 4.1.
  p2.cancel();
}

function test5(){
  // Create a resolved promise p1 that is adoping the state of a pending
  // promise.
  var p1 = new legendary.Promise(function(resolve){
    resolve(new legendary.Promise(function(resolve){
      setTimeout(resolve, 2000, "test5");
    }));
  });

  p1.then(function(value){
    console.log("5.1:", value);
  }, function(reason){
    console.log("5.1:", reason, reason.stack);
    throw reason;
  });
  var p2 = p1.then(null, function(reason){
    console.log("5.2:", reason, reason.stack);
    throw reason;
  });
  p2.then(null, function(reason){
    console.log("5.3:", reason, reason.stack);
  });

  // Cancelling p1 cancels adoption, which means all promise derived from
  // p1 get cancelled.
  p1.cancel();
}

function test6(){
  // Create a resolved promise p1 that is adoping the state of a pending
  // promise.
  var p1 = new legendary.Promise(function(resolve){
    resolve(new legendary.Promise(function(resolve){
      setTimeout(resolve, 2000, "test6");
    }));
  });

  p1.then(function(value){
    console.log("6.1:", value);
  }, function(reason){
    console.log("6.1:", reason, reason.stack);
    throw reason;
  });
  var p2 = p1.then(null, function(reason){
    console.log("6.2:", reason, reason.stack);
    throw reason;
  });
  p2.then(null, function(reason){
    console.log("6.3:", reason, reason.stack);
  });

  // Cancelling p2 propagates to p1, which means that all promises derived
  // from p1 get cancelled.
  p2.cancel();
}

function test7(){
  // Create a pending promise p1 with an onCancelled callback.
  var p1 = new legendary.Promise(function(resolve){
    var id = setTimeout(resolve, 2000, "test7");
    this.onCancelled = function(){
      console.log("7.onCancelled");
      clearTimeout(id);
    };
  });

  p1.then(function(value){
    console.log("7.1:", value);
  }, function(reason){
    console.log("7.1:", reason, reason.stack);
    throw reason;
  });
  var p2 = p1.then(null, function(reason){
    console.log("7.2:", reason, reason.stack);
    throw reason;
  });
  p2.then(null, function(reason){
    console.log("7.3:", reason, reason.stack);
  });

  // Cancelling p1 invokes the callback and means that all derived promises
  // get cancelled too.
  p1.cancel();
}