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[api-minor] Remove support for synchronous event dispatching in LoopbackPort

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*Please note:* The `defer` parameter has been enabled by default ever since PR 9777 (in 2018), which first shipped in PDF.js release `2.0.943`.
With workers *disabled*, e.g. in Node.js environments, this has been used ever since without any problems reported[1].

The impetus for this change was that I happened to notice that *if* the `LoopbackPort` was used with synchronous event dispatching, we'd simply send that data as-is to the listeners. This created an inconsistency in the data returned from the `pdf.worker.js` file, since `postMessage` used with *actual* workers (or the `LoopbackPort` with `defer = true`) will ignore/throw when encountering unclonable data.
Originally my intention was simply to just call `cloneValue` regardless of the event dispatching used in `LoopbackPort`, however looking at the use-cases (or lack thereof) of the `LoopbackPort` it seemed reasonable to simply remove the `defer` parameter instead.

This patch is tagged "[api-minor]" since the `LoopbackPort` is still exposed in the API, although I really hope that no third-party is using this (since disabling workers leads to bad performance).

Finally, this patch changes a `forEach` loop to `for...of` and makes uses of optional changing in existing code.

---
[1] As evident by the `npm test` command run by Github Actions, and previously by Travis.
This commit is contained in:
Jonas Jenwald 2021-02-17 15:52:01 +01:00
parent 952bc08ec0
commit 3398070e26
1 changed files with 7 additions and 14 deletions
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21
src/display/api.js
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@ -1624,9 +1624,8 @@ class PDFPageProxy {
}
class LoopbackPort {
constructor(defer = true) {
constructor() {
this._listeners = [];
this._defer = defer;
this._deferred = Promise.resolve(undefined);
}
@ -1670,7 +1669,7 @@ class LoopbackPort {
continue;
}
if (typeof desc.value === "function") {
if (value.hasOwnProperty && value.hasOwnProperty(i)) {
if (value.hasOwnProperty?.(i)) {
throw new Error(
`LoopbackPort.postMessage - cannot clone: ${value[i]}`
);
@ -1682,19 +1681,13 @@ class LoopbackPort {
return result;
}
if (!this._defer) {
this._listeners.forEach(listener => {
listener.call(this, { data: obj });
});
return;
}
const cloned = new WeakMap();
const e = { data: cloneValue(obj) };
const event = { data: cloneValue(obj) };
this._deferred.then(() => {
this._listeners.forEach(listener => {
listener.call(this, e);
});
for (const listener of this._listeners) {
listener.call(this, event);
}
});
}