Saturday, August 24, 2019

TenFourFox FPR16b1 available

TenFourFox Feature Parity Release 16 beta 1 is now available (downloads, hashes, release notes). In addition, the official FAQ has been updated, along with the tech notes.

FPR16 got delayed because I really tried very hard to make some progress on our two biggest JavaScript deficiencies, the infamous issues 521 (async and await) and 533 (this is undefined). Unfortunately, not only did I make little progress on either, but the speculative fix I tried for issue 533 turned out to be the patch that unsettled the optimized build and had to be backed out. There is some partial work on issue 521, though, including a fully working parser patch. The problem is plumbing this into the browser runtime which is ripe for all kinds of regressions and is not currently implemented (instead, for compatibility, async functions get turned into a bytecode of null throw null return, essentially making any call to an async function throw an exception because it wouldn't have worked in the first place).

This wouldn't seem very useful except that effectively what the whole shebang does is convert a compile-time error into a runtime warning, such that other functions that previously might not have been able to load because of the error can now be parsed and hopefully run. With luck this should improve the functionality of sites using these functions even if everything still doesn't fully work, as a down payment hopefully on a future implementation. It may not be technically possible but it's a start.

Which reminds me, and since this blog is syndicated on Planet Mozilla: hey, front end devs, if you don't have to minify your source, how about you don't? Issue 533, in fact, is entirely caused because uglify took some fast and loose shortcuts that barf on older parsers, and it is nearly impossible to unwind errors that occur in minified code (this is now changing as sites slowly update, so perhaps this will be self-limited in the end, but in the meantime it's as annoying as Andy Samberg on crack). This is particularly acute given that the only thing fixing it in the regression range is a 2.5 megabyte patch that I'm only a small amount of the way through reading. On the flip side, I was able to find and fix several parser edge cases because Bugzilla itself was triggering them and the source file that was involved was not minified. That means I could actually read it and get error reports that made sense! Help support us lonely independent browser makers by keeping our lives a little less complicated. Thank you for your consideration!

Meanwhile, I have the parser changes on by default to see if it induces any regressions. Sites may or may not work any differently, but they should not work worse. If you find a site that seems to be behaving adversely in the beta, please toggle javascript.options.asyncfuncs to false and restart the browser, which will turn the warning back into an error. If even that doesn't fix it, make sure nothing on the site changed (like, I dunno, checking it in FPR15) before reporting it in the comments.

This version also "repairs" Firefox Sync support by connecting the browser back up to the right endpoints. You are reminded, however, that like add-on support Firefox Sync is only supported at a "best effort" level because I have no control over the backend server. I'll make reasonable attempts to keep it working, but things can break at any time, and it is possible that it will stay broken for good (and be removed from the UI) if data structures or the protocol change in a way I can't control for. There's a new FAQ entry for this I suggest you read.

Finally, there are performance improvements for HTML5 and URL parsing from later versions of Firefox as well as a minor update to same-site cookie support, plus a fix for a stupid bug with SVG backgrounds that I caused and Olga found, updates to basic adblock with new bad hosts, updates to the font blacklist with new bad fonts, and the usual security and stability updates from the ESRs.

I realize the delay means there won't be a great deal of time to test this, so let me know deficiencies as quickly as possible so they can be addressed before it goes live on or about September 2 Pacific time.

1 comment:

Due to an increased frequency of spam, comments are now subject to moderation.