In commit edd37de8 we enable polyglossia for LuaTeX. Polyglossia has support for more languages. A significant amount of export tests that did not pass when using babel now pass using polyglossia (see b2e49892) because of this extra support.
This change also caused many of our export tests to fail. Some of these tests fail because we have babel-specific code in the preambles of our documentation. I'm not that worried about these failures (although some users will likely be hit by this chcange). I'm more worried that enabling polyglossia for LuaTeX exposes an existing bug in our LaTeX export of nested language environments. If export of our own documents run into this bug, then it is likely than many users will run into this bug as well. In some sense edd37de8 does not introduce any *new* bug into LyX, but it makes an existing bug hit the user in more ways. It is true that the same bug has existed with respect to XeTeX and polyglossia for years and we have not received many bug reports because of it. The other side of this argument is that no one has made a feature request or bug report that edd37de8 solves. Jürgen has improved the situation at b1c68dcc. However, I think he does not have any time to fix the remaining issues of #9633 before the 2.2.0 release. Does anyone have time and interest to look into fixing #9633? I have the feeling that it is a difficult one to tackle. If someone is interested, I can work with you to run the tests and tell which of our export tests are failing because of the bug so you have examples to work with. Scott
