Today's (2019-02-09) tlmgr update of TeXLive 2018 (on Linux) broke my project (around twelve hundred pages in several books typeset with LuaLaTeX using Adobe Garamond Pro) severely — almost all the pages were modified badly in huge measure. I had to restore the package luaotfload to its previous version (from broken version 49978):

tlmgr restore luaotfload 49747


After that the books compiled OK again.

Edited later Seems the broken version of luaotdload causes fontspec LetterSpace instruction to be ignored.

Here comes some MWE (might be perhaps more minimalized, this is a quick extract of settings — obviously modified to extreme to display the problem — in my project (the text of which I do not own the copyright so I cannot use it here, but this should be enough)):

%%%! LuaLaTeX

\documentclass[11pt,twoside,openright]{book}

\usepackage{fontspec}
\defaultfontfeatures{
Ligatures = { TeX, Common, },
ItalicFeatures = { LetterSpace = 10 },
Numbers = { Proportional },
}
\usepackage{polyglossia}
\setdefaultlanguage{czech}
\setotherlanguage{esperanto}
\usepackage[
protrusion = true,
expansion = true,
tracking = true,
factor = 800,
stretch = 15,
shrink = 15
]{microtype}

\begin{document}

\textit{Příliš žluťoučký kůň úpěl ďábelské ódy.}

{
Some text with huge spacing
}

\end{document}


Here is the result (correct is with the previous version of luaotdfload (49747), bad with the current version (49978):

Edit: the same problem occurs with Libertinus, just use:

\setmainfont{libertinusserif}


Even shorter MWE:

\documentclass{article}

\usepackage{fontspec}
\setmainfont[LetterSpace = 150]{Latin Modern Roman}

\begin{document}
Some text with huge spacing
\end{document}

• No need for TeX Live people to read this. As you may read in the manual the home of luaotfload is github.com/u-fischer/luaotfload (i.e. there's an issue tracker and not a mailing list…). – TeXnician Feb 9 at 11:56
• I can understand your frustration, but please note that this site is neither the place to report bugs in packages nor a place to rant about the development of packages. As such I feel that while this question could certainly go somewhere (for example with a short document that reproduces undesirable behaviour) in its current form it is off-topic here. – moewe Feb 9 at 11:56
• Btw: It's hard to answer the question whether the package is broken without seeing how you use it. Maybe it's a simple user error that happened to work earlier. So a MWE that compiles with the old version and is messed up with the new one would be very helpful for us to help you. – TeXnician Feb 9 at 11:59
• -1: (aside from the unnecessary rude language) Test the stuff before you update, if it is that important. This is true for free and commercial software. – Dr. Manuel Kuehner Feb 9 at 12:10
• @moewe Yes it appears to be the same problem. Thanks for the real M in MWE. – Marcel S. Feb 10 at 18:20