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Introduce abortSignal.throwIfAborted() #1034

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Dec 10, 2021
Merged

Introduce abortSignal.throwIfAborted() #1034

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748e15c
Introduce abortSignal.throwIfAborted()
domenic Nov 23, 2021
0645ef6
use it in doAmazingness example
annevk Dec 6, 2021
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41 changes: 34 additions & 7 deletions dom.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -1695,11 +1695,9 @@ controller.abort();</code></pre>

<pre><code class=lang-javascript>
function doAmazingness({signal}) {
if (signal.aborted) {
return Promise.reject(signal.reason);
}

return new Promise((resolve, reject) => {
signal.throwIfAborted();

// Begin doing amazingness, and call resolve(result) when done.
// But also, watch for signals:
signal.addEventListener('abort', () => {
Expand Down Expand Up @@ -1776,6 +1774,7 @@ interface AbortSignal : EventTarget {

readonly attribute boolean aborted;
readonly attribute any reason;
undefined throwIfAborted();

attribute EventHandler onabort;
};</pre>
Expand All @@ -1786,11 +1785,14 @@ interface AbortSignal : EventTarget {
<var>reason</var> if not undefined; otherwise to an "{{AbortError!!exception}}" {{DOMException}}.

<dt><code><var>signal</var> . <a attribute for=AbortSignal>aborted</a></code>
<dd>Returns true if this {{AbortSignal}}'s {{AbortController}} has signaled to abort; otherwise
false.
<dd>Returns true if <var>signal</var>'s {{AbortController}} has signaled to abort; otherwise false.

<dt><code><var>signal</var> . <a attribute for=AbortSignal>reason</a></code>
<dd>Returns this {{AbortSignal}}'s <a for=AbortSignal>abort reason</a>.
<dd>Returns <var>signal</var>'s <a for=AbortSignal>abort reason</a>.

<dt><code><var>signal</var> . <a method for=AbortSignal lt=throwIfAborted()>throwIfAborted</a>()</code>
<dd>Throws <var>signal</var>'s <a for=AbortSignal>abort reason</a>, if <var>signal</var>'s
{{AbortController}} has signaled to abort; otherwise, does nothing.
</dl>

<p>An {{AbortSignal}} object has an associated <dfn export for=AbortSignal>abort reason</dfn>, which is a
Expand Down Expand Up @@ -1840,6 +1842,31 @@ is [=AbortSignal/aborted=]; otherwise false.
<p>The <dfn attribute for=AbortSignal>reason</dfn> getter steps are to return <a>this</a>'s
<a for=AbortSignal>abort reason</a>.

<p>The <dfn method for=AbortSignal>throwIfAborted()</dfn> method steps are to throw <a>this</a>'s
<a for=AbortSignal>abort reason</a>, if <a>this</a> is [=AbortSignal/aborted=].

<div class=example id=example-throwifaborted>
<p>This method is primarily useful for when functions accepting {{AbortSignal}}s want to throw (or
return a rejected promise) at specific checkpoints, instead of passing along the {{AbortSignal}}
to other methods. For example, the following function allows aborting in between each attempt to
poll for a condition. This gives opportunities to abort the polling process, even though the
actual asynchronous operation (i.e., <code class=lang-javascript>await func()</code>) does not
accept an {{AbortSignal}}.

<pre class=lang-javascript>
async function waitForCondition(func, targetValue, { signal } = {}) {
while (true) {
signal?.throwIfAborted();

const result = await func();
if (result === targetValue) {
return;
}
}
}
</pre>
</div>

<p>The <dfn attribute for=AbortSignal><code>onabort</code></dfn> attribute is an
<a>event handler IDL attribute</a> for the <dfn export for=AbortSignal><code>onabort</code></dfn>
<a>event handler</a>, whose <a>event handler event type</a> is
Expand Down