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Promise-subclassing.html
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<!doctype html>
<meta charset=utf-8>
<title></title>
<script src=/resources/testharness.js></script>
<script src=/resources/testharnessreport.js></script>
<script>
var theLog = [];
var speciesGets = 0;
var speciesCalls = 0;
var constructorCalls = 0;
var constructorGets = 0;
var resolveCalls = 0;
var rejectCalls = 0;
var thenCalls = 0;
var catchCalls = 0;
var allCalls = 0;
var raceCalls = 0;
var nextCalls = 0;
function takeLog() {
var oldLog = theLog;
theLog = [];
speciesGets = speciesCalls = constructorCalls = resolveCalls =
rejectCalls = thenCalls = catchCalls = allCalls = raceCalls =
nextCalls = constructorGets = 0;
return oldLog;
}
function clearLog() {
takeLog();
}
function log(str) {
theLog.push(str);
}
class LoggingPromise extends Promise {
constructor(func) {
super(func);
Object.defineProperty(this, "constructor",
{
get: function() {
++constructorGets;
log(`Constructor get ${constructorGets}`);
return Object.getPrototypeOf(this).constructor;
}
});
++constructorCalls;
log(`Constructor ${constructorCalls}`);
}
static get [Symbol.species]() {
++speciesGets;
log(`Species get ${speciesGets}`);
return LoggingSpecies;
}
static resolve(val) {
++resolveCalls;
log(`Resolve ${resolveCalls}`);
return super.resolve(val);
}
static reject(val) {
++rejectCalls;
log(`Reject ${rejectCalls}`);
return super.reject(val);
}
then(resolve, reject) {
++thenCalls;
log(`Then ${thenCalls}`);
return super.then(resolve, reject);
}
catch(handler) {
++catchCalls;
log(`Catch ${catchCalls}`);
return super.catch(handler);
}
static all(val) {
++allCalls;
log(`All ${allCalls}`);
return super.all(val);
}
static race(val) {
++raceCalls;
log(`Race ${raceCalls}`);
return super.race(val);
}
}
class LoggingIterable {
constructor(array) {
this.iter = array[Symbol.iterator]();
}
get [Symbol.iterator]() { return () => this }
next() {
++nextCalls;
log(`Next ${nextCalls}`);
return this.iter.next();
}
}
class LoggingSpecies extends LoggingPromise {
constructor(func) {
++speciesCalls;
log(`Species call ${speciesCalls}`);
super(func)
}
}
class SpeciesLessPromise extends LoggingPromise {
static get [Symbol.species]() {
return undefined;
}
}
promise_test(function testBasicConstructor() {
var p = new LoggingPromise((resolve) => resolve(5));
var log = takeLog();
assert_array_equals(log, ["Constructor 1"]);
assert_true(p instanceof LoggingPromise);
return p.then(function(arg) {
assert_equals(arg, 5);
});
}, "Basic constructor behavior");
promise_test(function testPromiseRace() {
clearLog();
var p = LoggingPromise.race(new LoggingIterable([1, 2]));
var log = takeLog();
assert_array_equals(log, ["Race 1", "Constructor 1",
"Next 1", "Resolve 1", "Constructor 2",
"Then 1", "Constructor get 1", "Species get 1", "Species call 1", "Constructor 3",
"Next 2", "Resolve 2", "Constructor 4",
"Then 2", "Constructor get 2", "Species get 2", "Species call 2", "Constructor 5",
"Next 3"]);
assert_true(p instanceof LoggingPromise);
return p.then(function(arg) {
assert_in_array(arg, [1, 2]);
});
}, "Promise.race behavior");
promise_test(function testPromiseRaceNoSpecies() {
clearLog();
var p = SpeciesLessPromise.race(new LoggingIterable([1, 2]));
var log = takeLog();
assert_array_equals(log, ["Race 1", "Constructor 1",
"Next 1", "Resolve 1", "Constructor 2",
"Then 1", "Constructor get 1",
"Next 2", "Resolve 2", "Constructor 3",
"Then 2", "Constructor get 2",
"Next 3"]);
assert_true(p instanceof SpeciesLessPromise);
return p.then(function(arg) {
assert_in_array(arg, [1, 2]);
});
}, "Promise.race without species behavior");
promise_test(function testPromiseAll() {
clearLog();
var p = LoggingPromise.all(new LoggingIterable([1, 2]));
var log = takeLog();
assert_array_equals(log, ["All 1", "Constructor 1",
"Next 1", "Resolve 1", "Constructor 2",
"Then 1", "Constructor get 1", "Species get 1", "Species call 1", "Constructor 3",
"Next 2", "Resolve 2", "Constructor 4",
"Then 2", "Constructor get 2", "Species get 2", "Species call 2", "Constructor 5",
"Next 3"]);
assert_true(p instanceof LoggingPromise);
return p.then(function(arg) {
assert_array_equals(arg, [1, 2]);
});
}, "Promise.all behavior");
promise_test(function testPromiseResolve() {
clearLog();
var p = LoggingPromise.resolve(5);
var log = takeLog();
assert_array_equals(log, ["Resolve 1", "Constructor 1"]);
var q = LoggingPromise.resolve(p);
assert_equals(p, q,
"Promise.resolve with same constructor should preserve identity");
log = takeLog();
assert_array_equals(log, ["Resolve 1", "Constructor get 1"]);
var r = Promise.resolve(p);
log = takeLog();
assert_array_equals(log, ["Constructor get 1"]);
assert_not_equals(p, r,
"Promise.resolve with different constructor should " +
"create a new Promise instance (1)")
var s = Promise.resolve(6);
var u = LoggingPromise.resolve(s);
log = takeLog();
assert_array_equals(log, ["Resolve 1", "Constructor 1"]);
assert_not_equals(s, u,
"Promise.resolve with different constructor should " +
"create a new Promise instance (2)")
Object.defineProperty(s, "constructor", { value: LoggingPromise });
var v = LoggingPromise.resolve(s);
log = takeLog();
assert_array_equals(log, ["Resolve 1"]);
assert_equals(v, s, "Faking the .constructor should work");
assert_false(v instanceof LoggingPromise);
var results = Promise.all([p, q, r, s, u, v]);
return results.then(function(arg) {
assert_array_equals(arg, [5, 5, 5, 6, 6, 6]);
});
}, "Promise.resolve behavior");
promise_test(function testPromiseReject() {
clearLog();
var p = LoggingPromise.reject(5);
var log = takeLog();
assert_array_equals(log, ["Reject 1", "Constructor 1"]);
return p.catch(function(arg) {
assert_equals(arg, 5);
});
}, "Promise.reject behavior");
promise_test(function testPromiseThen() {
clearLog();
var p = LoggingPromise.resolve(5);
var log = takeLog();
assert_array_equals(log, ["Resolve 1", "Constructor 1"]);
var q = p.then((x) => x*x);
log = takeLog();
assert_array_equals(log, ["Then 1", "Constructor get 1", "Species get 1",
"Species call 1", "Constructor 1"]);
assert_true(q instanceof LoggingPromise);
return q.then(function(arg) {
assert_equals(arg, 25);
});
}, "Promise.then behavior");
promise_test(function testPromiseCatch() {
clearLog();
var p = LoggingPromise.reject(5);
var log = takeLog();
assert_array_equals(log, ["Reject 1", "Constructor 1"]);
var q = p.catch((x) => x*x);
log = takeLog();
assert_array_equals(log, ["Catch 1", "Then 1", "Constructor get 1",
"Species get 1", "Species call 1", "Constructor 1"]);
assert_true(q instanceof LoggingPromise);
return q.then(function(arg) {
assert_equals(arg, 25);
});
}, "Promise.catch behavior");
</script>