This particular JSDoc comment is fairly old and it also contains some now unrelated/confusing information.
The only way to *guarantee* that the PDF.js library works as expected is to correctly set the global `workerSrc`[1], hence giving the impression that the option isn't strictly necessary is thus incorrect.
---
[1] Since advertising the fallbackWorkerSrc functionality definitely seems like the *wrong* thing to do.
Note that Prettier, purposely, has only limited [configuration options](https://prettier.io/docs/en/options.html). The configuration file is based on [the one in `mozilla central`](https://searchfox.org/mozilla-central/source/.prettierrc) with just a few additions (to avoid future breakage if the defaults ever changes).
Prettier is being used for a couple of reasons:
- To be consistent with `mozilla-central`, where Prettier is already in use across the tree.
- To ensure a *consistent* coding style everywhere, which is automatically enforced during linting (since Prettier is used as an ESLint plugin). This thus ends "all" formatting disussions once and for all, removing the need for review comments on most stylistic matters.
Many ESLint options are now redundant, and I've tried my best to remove all the now unnecessary options (but I may have missed some).
Note also that since Prettier considers the `printWidth` option as a guide, rather than a hard rule, this patch resorts to a small hack in the ESLint config to ensure that *comments* won't become too long.
*Please note:* This patch is generated automatically, by appending the `--fix` argument to the ESLint call used in the `gulp lint` task. It will thus require some additional clean-up, which will be done in a *separate* commit.
(On a more personal note, I'll readily admit that some of the changes Prettier makes are *extremely* ugly. However, in the name of consistency we'll probably have to live with that.)
Compared to most other options currently/previously residing on the global `PDFJS` object, some of the Worker specific ones (e.g. `workerPort`/`workerSrc`) probably cannot be moved into options provided directly when initializing e.g. `PDFWorker`.
The reason is that in some cases, e.g. the Webpack examples, we try to provide Worker auto-configuration and I cannot see a good solution for that use-case if we completely remove the globally available Worker configuration.
However inline with previous patches for PDF.js version `2.0`, it does seem like a worthwhile goal to move away from storing options directly on the global `PDFJS` object, since that is a pattern we should avoid going forward. Especially since one of the (eventual) goals is to attempt to *completely* remove the global `PDFJS` object, and rely solely on exporting/importing the needed functionality.
By introducing the `GlobalWorkerOptions` we thus have larger flexibility in the future, if/when the global `PDFJS` object will be removed.
