I recently noticed a couple of intermittent failures on Travis, hence this patch which changes the expectation to be identical to the 'Page Request' check in the preceding test-case.
https://npmjs.com/advisories/1084
webpack-stream between 4.0.3 and 5.0.0 added official support for Webpack 4. Which is nice since we ARE using Webpack 4... Also, dropped support for Node.js 4 which shouldn't be a big deal for us since we are already using packages that are incompatible with Node.js 4 (Webpack 4.x supports Node.js 6 and up).
Since bundlers, such as Webpack, cannot be told to leave `require` statements alone we are thus forced to jump through hoops in order to prevent these warnings in third-party deployments of the PDF.js library; please see [Webpack issue 8826](https://github.com/webpack/webpack) and libraries such as [require-fool-webpack](https://github.com/sindresorhus/require-fool-webpack).
*Please note:* This is based on the assumption that code running in Node.js won't ever be affected by e.g. Content Security Policies that prevent use of `eval`. If that ever occurs, we should revert to a normal `require` statement and simply document the Webpack warnings instead.
This patch reduces some duplication, by moving *all* fake worker loader code into the `setupFakeWorkerGlobal` function. Furthermore, the functions are simplified further by using `async`/`await` where appropriate.
There's no particularily good reason, as far as I can tell, to not support a custom worker path in Node.js environments (even if workers aren't supported). This patch thus make the Node.js fake worker loader code-path consistent with the fallback code-path used with *browser* fake worker loader.
Finally, this patch also deprecates[1] the `fallbackWorkerSrc` functionality, except in Node.js, since the user should *always* provide correct worker options since the fallback is nothing more than a best-effort solution.
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[1] Although it probably shouldn't be removed until the next major version.
For performance reasons, and to avoid hanging the browser UI, the PDF.js library should *always* be used with web workers enabled.
At this point in time all of the supported browsers should have proper worker support, and Node.js is thus the only environment where workers aren't supported. Hence it no longer seems relevant/necessary to provide, by default, fake worker loaders for various JS builders/bundlers/frameworks in the PDF.js code itself.[1]
In order to simplify things, the fake worker loader code is thus simplified to now *only* support Node.js usage respectively "normal" browser usage out-of-the-box.[2]
*Please note:* The officially intended way of using the PDF.js library is with workers enabled, which can be done by setting `GlobalWorkerOptions.workerSrc`, `GlobalWorkerOptions.workerPort`, or manually providing a `PDFWorker` instance when calling `getDocument`.
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[1] Note that it's still possible to *manually* disable workers, simply my manually loading the built `pdf.worker.js` file into the (current) global scope, however this's mostly intended for testing/debugging purposes.
[2] Unfortunately some bundlers such as Webpack, when used with third-party deployments of the PDF.js library, will start to print `Critical dependency: ...` warnings when run against the built `pdf.js` file from this patch. The reason is that despite the `require` calls being protected by *runtime* `isNodeJS` checks, it's not possible to simply tell Webpack to just ignore the `require`; please see [Webpack issue 8826](https://github.com/webpack/webpack) and libraries such as [require-fool-webpack](https://github.com/sindresorhus/require-fool-webpack).
*Please note:* This patch does *not* prevent the 'default_preferences' task from running more than once during `npm test`, but it does ensure that the tasks won't run *concurrently* by running the relevant tests in *series*.
While it would obviously still make sense to re-factor the gulpfile to account for changes in `gulp` version 4, by at least tweaking the `npm test` command the intermittent failures on Travis should at least go away.
During initial parsing of every PDF document we're currently creating a few `1 kB` strings, in order to find certain commands needed for initialization.
This seems inefficient, not to mention completely unnecessary, since we can just as well search through the raw bytes directly instead (similar to other parts of the code-base). One small complication here is the need to support backwards search, which does add some amount of "duplication" to this function.
The main benefits here are:
- No longer necessary to allocate *temporary* `1 kB` strings during initial parsing, thus saving some memory.
- In practice, for well-formed PDF documents, the number of iterations required to find the commands are usually very low. (For the `tracemonkey.pdf` file, there's a *total* of only 30 loop iterations.)
Looking at the `parseCurrentHash` function again it's now difficult for me to understand *what* I was thinking, since having a helper function that needs to be manually passed a `linkService` reference just looks weird.
This patch addresses a couple of smaller issues with the `PDFHistory` class:
- Most, if not all, other viewer components can be reset in one way or another, and there's no good reason for the `PDFHistory` implementation to be different here.
- Currently it's (technically) possible to keep adding entries to the browser history, via the `PDFHistory` instance, even after the document has been closed. That obviously makes no sense, and is caused by the lack of a `reset` method.
- The internal `this._isPagesLoaded` property was never actually reset, which would lead to it being temporarily wrong when a new document was opened in the default viewer.
Note that most (reasonably) modern browsers have supported this for a while now, see https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream#Browser_compatibility
By moving the polyfill into `src/shared/compatibility.js` we can thus get rid of the need to manually export/import `ReadableStream` and simply use it directly instead.
The only change here which *could* possibly lead to a difference in behavior is in the `isFetchSupported` function. Previously we attempted to check for the existence of a global `ReadableStream` implementation, which could now pass (assuming obviously that the preceding checks also succeeded).
However I'm not sure if that's a problem, since the previous check only confirmed the existence of a native `ReadableStream` implementation and not that it actually worked correctly. Finally it *could* just as well have been a globally registered polyfill from an application embedding the PDF.js library.
Given that the error in question is surfaced on the API-side, this patch makes the following changes:
- Updates the wording such that it'll hopefully be slightly easier for users to understand.
- Changes the plain `Error` to an `InvalidPDFException` instead, since that should work better with the existing Error handling.
- Adds a unit-test which loads an empty PDF document (and also improves a pre-existing `InvalidPDFException` message and its test-case).
