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Allow async functions to throw #178

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Allow async functions to throw #178

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68bb747
Allow async functions to throw
cpcallen Jan 30, 2020
22f6493
Async callback with no args should return
cpcallen Mar 2, 2020
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23 changes: 20 additions & 3 deletions demos/async.html
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Original file line number Diff line number Diff line change
Expand Up @@ -19,8 +19,16 @@
var req = new XMLHttpRequest();
req.open('GET', href, true);
req.onreadystatechange = function() {
if (req.readyState == 4 && req.status == 200) {
callback(req.responseText);
if (req.readyState == 4) {
if(req.status == 200) {
callback(req.responseText);
} else {
var error = interpreter.createObject(interpreter.ERROR);
interpreter.setProperty(error, 'message',
req.status + req.statusText,
Interpreter.NONENUMERABLE_DESCRIPTOR);
callback(undefined, error);
}
}
};
req.send(null);
Expand Down Expand Up @@ -102,11 +110,20 @@ <h1>JS-Interpreter Async Demo</h1>
will both do nothing, returning <code>true</code> to indicate that the program
still has code to execute.</p>

<p>The callback takes one or two arguments. If called with one, the
supplied value is used as the return value of the asynchronous
call. If called with two, the first is ignored and the second is
used as the value of an exception thrown by the call.</p>

<p>Click <em>Parse</em>, then either click <em>Step</em> repeatedly,
or click <em>Run</em> once. Open your browser's console for errors.</p>

<p><textarea id="code">
alert(getXhr('async.txt'));
try {
alert(getXhr('async.txt'));
} catch(e) {
alert('Failed: ' + e);
}
</textarea><br>
<button onclick="parseButton()">Parse</button>
<button onclick="stepButton()" id="stepButton" disabled="disabled">Step</button>
Expand Down
9 changes: 7 additions & 2 deletions interpreter.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3226,8 +3226,13 @@ Interpreter.prototype['stepCallExpression'] = function(stack, state, node) {
state.value = func.nativeFunc.apply(state.funcThis_, state.arguments_);
} else if (func.asyncFunc) {
var thisInterpreter = this;
var callback = function(value) {
state.value = value;
var callback = function(value, exception) {
if (arguments.length <= 1) {
state.value = value;
} else {
thisInterpreter.unwind(Interpreter.Completion.THROW,
exception, undefined);
}
thisInterpreter.paused_ = false;
};
// Force the argument lengths to match, then append the callback.
Expand Down