Currently we simply use the Babel `preset-env` in the `legacy`-builds of the PDF.js library. This has the side-effect of transpiling the code for *very old* browsers/environments, including ones that we (since many years) no longer support which unnecessarily bloats the size of the `legacy`-builds.
For the CSS files we're only targeting *the supported browsers*, and it's thus possible to extend that to also apply to Babel.
One of the most significant changes, with this patch, is that we'll no longer polyfill `async`/`await` in the `legacy`-builds. However, this shouldn't be an issue given the browsers that we currently support in PDF.js; please refer to:
- https://github.com/mozilla/pdf.js/wiki/Frequently-Asked-Questions#faq-support
- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function#browser_compatibility
Rather than including all of this external code in the PDF.js repository, we should be using the npm package instead.
Unfortunately this is slightly more complicated than you'd hope, since the `fit-curve` package (which is older) isn't directly compatible with modern JavaScript modules.
In particular, the following cases needed to be considered:
- For the development viewer (i.e. `gulp server`) and the unit-tests, we thus need to build a fitCurve-bundle that can be directly `import`ed.
- For the actual PDF.js build-targets, we can slightly reduce the sizes by depending on the "raw" `fit-curve` source-code.
- For the Node.js unit-tests, the `fit-curve` package can be used as-is.
Note that even though Puppeteer got a major version bump the changelog
doesn't include compatibility changes that are relevant to us; please
see https://github.com/puppeteer/puppeteer/releases.
Unfortunately newer versions either caused breakage when running the
unit tests manually in a browser or when serving the development viewer.
Given that we hope to use native import maps soon and this dependency
will then be removed anyway, let's pin it for the time being.
There are two notable changes here:
- `dommatrix` is a major version upgrade, but looking through the commit
history of their `package.json` file at https://github.com/thednp/dommatrix/commits/master/package.json
(due to the lack of a changelog) I couldn't find any breaking changes.
- `es-module-shims` is a regular update, but it was previously pinned
for causing intermittent breakage when running the unit tests in a
browser manually. Fortunately this cannot be reproduced anymore with
the most recent version, so we can also put the caret back now.
Because of a bug in previous `core-js` versions, which caused an Error to be thrown if its `structuredClone` polyfill was called with an *explicit* `null`/`undefined` transfer-parameter, the `LoopbackPort`-class contained a work-around.
In the latest `core-js` version this has been fixed, and we can thus simplify our code ever so slightly; please see https://github.com/zloirock/core-js/releases/tag/v3.22.0
Please note that this patch is purposely quite basic, e.g. it doesn't add the polyfill-CSS in order to simplify the build process, and things such as `::backdrop` thus isn't working.
However, this patch does ensure that older browsers can at least still *access* all of the previous overlays and that things like e.g. opening of password-protected documents respectively printing still works.
Note that the Prettier update made it possible to move a couple of comments after `default:`-cases back to their original/intended positions, please see https://prettier.io/blog/2022/03/16/2.6.0.html
Since the Autoprefixer plugin indirectly depends on this, it seems like a good idea to add this as a direct dependency in the PDF.js project to hopefully avoid having to manually update `caniuse-lite` in the future; see https://github.com/browserslist/browserslist#browsers-data-updating
Also, slightly tweaks the Autoprefixer config for GENERIC-builds of the PDF.js library; note that this change doesn't affect the contents of the *built* `web/viewer.js` file.
This allows us to remove the manually implemented `structuredClone` polyfill, thus reducing the maintenance burden for the `LoopbackPort` class; refer to https://github.com/zloirock/core-js#structuredclone
*Please note:* While `structuredClone` support landed already in Firefox 94, Google Chrome only added it in version 98 (currently in Beta). However, given that the `LoopbackPort` will only be used together with *fake workers* in browsers this shouldn't be too much of a problem.[1]
For Node.js environments, where *fake workers* are unfortunately necessary, using a `legacy/`-build is already required which thus guarantees that the `structuredClone` polyfill is available.
Also, the patch updates core-js to the latest version since that one includes `structuredClone` improvements; please see https://github.com/zloirock/core-js/releases/tag/v3.20.3
---
[1] Given that we only support browsers with proper worker support, if *fake workers* are being used that essentially indicates a configuration problem/error.
This patch circumvents the issues seen when trying to update TypeScript to version `4.5`, by "simply" fixing the broken/missing JSDocs and `typedef`s such that `gulp typestest` now passes.
As always, given that I don't really know anything about TypeScript, I cannot tell if this is a "correct" and/or proper way of doing things; we'll need TypeScript users to help out with testing!
*Please note:* I'm sorry about the size of this patch, but given how intertwined all of this unfortunately is it just didn't seem easy to split this into smaller parts.
However, one good thing about this TypeScript update is that it helped uncover a number of pre-existing bugs in our JSDocs comments.
Since NPM 7, which is over a year old now since it released in October
2020, NPM automatically transforms lock files from version 1 to version
2. In the NPM 7 release notes they reported:
"One change to take note of is the new lockfile format, which is
backwards compatible with npm 6 users. The lockfile v2 unlocks the
ability to do deterministic and reproducible builds to produce a
package tree."
Not only is this change backwards compatible (so older versions of NPM
will still be able to install everything as expected), reproducability
is also a nice property to have and modern NPM versions will otherwise
constantly do the conversion anyway, causing contributors to explicitly
have to revert the change. Therefore, I believe we should do this now
since it doesn't break backwards compatibility for consumers of this
file. It only means that producers of this file (i.e., us contributors)
need to use at least NPM 7 or higher (as of writing NPM 8 is even
available). According to https://nodejs.org/en/download/releases/ this
means contributors should at least run Node.js 15.0.0, while 17.1.0 is
the most recent as of writing, so to me that sounds reasonable to ask.
