- For the generic viewer we use @fluent/dom and @fluent/bundle
- For the builtin pdf viewer in Firefox, we set a localization url
and then we rely on document.l10n which is a DOMLocalization object.
At this point in time all browsers, and also Node.js, support standard `import`/`export` statements and we can now finally consider outputting modern JavaScript modules in the builds.[1]
In order for this to work we can *only* use proper `import`/`export` statements throughout the main code-base, and (as expected) our Node.js support made this much more complicated since both the official builds and the GitHub Actions-based tests must keep working.[2]
One remaining issue is that the `pdf.scripting.js` file cannot be built as a JavaScript module, since doing so breaks PDF scripting.
Note that my initial goal was to try and split these changes into a couple of commits, however that unfortunately didn't really work since it turned out to be difficult for smaller patches to work correctly and pass (all) tests that way.[3]
This is a classic case of every change requiring a couple of other changes, with each of those changes requiring further changes in turn and the size/scope quickly increasing as a result.
One possible "issue" with these changes is that we'll now only output JavaScript modules in the builds, which could perhaps be a problem with older tools. However it unfortunately seems far too complicated/time-consuming for us to attempt to support both the old and modern module formats, hence the alternative would be to do "nothing" here and just keep our "old" builds.[4]
---
[1] The final blocker was module support in workers in Firefox, which was implemented in Firefox 114; please see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import#browser_compatibility
[2] It's probably possible to further improve/simplify especially the Node.js-specific code, but it does appear to work as-is.
[3] Having partially "broken" patches, that fail tests, as part of the commit history is *really not* a good idea in general.
[4] Outputting JavaScript modules was first requested almost five years ago, see issue 10317, and nowadays there *should* be much better support for JavaScript modules in various tools.
"text/javascript" is not a correct MIME type (the correct one is
"application/javascript") but it's not even needed; all browsers default
to the correct type and treat it as executable JS when type is ommited.
Since not all browsers recognize the "application/javascript" MIME type
the only way to both stay compliant and to support all popular browsers
is to omit the type. It's also shorter this way.
Before commit:
chrome-extension://EXTENSIONID/content/web/viewer.html?file=http%3A%2F%2Fexample.com%2Ffile.pdf
After commit:
chrome-extension://EXTENSIONID/http://example/file.pdf
Technical details:
- The extension's background page uses the webRequest API to intercept
requests for <extension host>/<real path to pdf>, and redirect it to
the viewer's URL.
- viewer.js uses history.replaceState to rewrite the URL, so that it's
easier for users to recognize and copy-paste URLs.
- The fake paths /http:, /https:, /file:, etc. have been added to the
web_accessible_resources section of the manifest file, in order to
avoid seeing chrome-extension://invalid/ instead of the actual URL
when using history back/forward to navigate from/to the PDF viewer.
- Since the relative path resolving doesn't work because relative URLs
are inaccurate, a <base> tag has been added. This method has already
been proven to work in the Firefox add-on.
Notes:
- This commit has been cherry-picked from crx-using-streams-api.
- Need to merge https://github.com/mozilla/pdf.js/pull/3582 to deal with
a bug in Chrome <=30
- In Chrome, getting the contents of a FTP file is not possible, so
there's no support for FTP files, even though the extension router
recognizes the ftp: scheme.
