Stefi writes: > It might be a change to texmathp.el. It is part of Auctex and checks if > math mode is on or off. I could not find align environment in the list > of default environments. Maybe that has changed. > > However, I added align and align* to "Texmathp Tex Commands" from the > customize browser (open a .tex file to customize auctex). Tab-expansion > is working now. Can anyone confirm? > > In my .emacs, it added to custom-set-variables: > '(texmathp-tex-commands (quote (("align*" env-on) ("align" env-on))))
Yes, that results in expansion on my end as well. It looks like this issue was introduced with AUCTeX's 91701704 (Delete overhead in extending font lock range of math expression, 2020-06-11). If you're getting AUCTeX from ELPA, the regression is included the current version there (12.2.4, 2020-06-29). At the start of this month, it was fixed in f04a508f (Restore all math environments in texmathp.el, 2020-08-01), so the issue should go away with the next update that lands on ELPA.