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Always use an implicit done callback #7

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Always use an implicit done callback #7

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337059b
Fix throwing errors into the generator
TomiBelan Aug 24, 2013
52b86fd
Always use an implicit done callback.
TomiBelan Aug 25, 2013
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23 changes: 10 additions & 13 deletions run.js
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Original file line number Diff line number Diff line change
Expand Up @@ -5,15 +5,20 @@ function run(generator, callback) {
var iterator = generator(resume);
var data = null, yielded = false;

var next = callback ? nextSafe : nextPlain;

if (!callback) callback = function (err) {
// If the generator ended with an error, throw it globally with setTimeout.
// Throwing locally from a callback is not allowed, and swallowing the
// error is a bad idea, so there's no better option.
if (err) setTimeout(function () { throw err; }, 0);
};

next();
check();

function nextSafe(item) {
function next(err, item) {
var n;
try {
n = iterator.next(item);
n = (err ? iterator.throw(err) : iterator.next(item));
if (!n.done) {
if (typeof n.value === "function") n.value(resume());
yielded = true;
Expand All @@ -25,13 +30,6 @@ function run(generator, callback) {
}
return callback(null, n.value);
}

function nextPlain(item) {
var cont = iterator.next(item).value;
// Pass in resume to continuables if one was yielded.
if (typeof cont === "function") cont(resume());
yielded = true;
}

function resume() {
var done = false;
Expand All @@ -49,8 +47,7 @@ function run(generator, callback) {
var item = data[1];
data = null;
yielded = false;
if (err) return iterator.throw(err);
next(item);
next(err, item);
yielded = true;
}
}
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30 changes: 27 additions & 3 deletions test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -70,7 +70,7 @@ function *run_with_callback(gen) {
console.log("Callback");
yield run(function* (gen) {
yield sleep(1000);
return "Hello"
return "Hello";
}, function (err, value) {
console.log("Callback err: " + err);
console.log("Callback value: " + value);
Expand Down Expand Up @@ -102,7 +102,25 @@ function *run_with_callback_early_exception(gen) {
console.log("Callback value: " + value);
gen()(null, value); // Intentionally suppress the error
});
console.log("End");
testRun("run_with_thrown_error", run_with_thrown_error);
}

function *run_with_thrown_error(gen) {
var inCatch = false;
try {
yield sleep(1);
yield fail();
console.error("this should not happen!");
}
catch (err) {
console.log("in catch: " + err);
console.assert(err);
inCatch = true;
}
yield sleep(1);
console.log("yielded after catch");
console.assert(inCatch);
console.log("\nEnd");
}

function sleep(ms) {
Expand All @@ -117,7 +135,13 @@ function evil() {
setTimeout(function () {
callback(null, 2);
}, 100);
}
};
}

function fail() {
return function (callback) {
callback(Error("throwing error into generator"));
};
}

function decrement(n) {
Expand Down