bug#53817: 28.0.91; sh-mode indent misses on 'if test; then' when 'then' is on 'if' line

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

> (defun sh-smie--default-backward-token ()
> [...]
>             (progn (skip-syntax-backward ".w_'")
>                    (or (not (zerop (skip-syntax-backward "\\")))
>                        (when (eq ?\\ (char-before (1- (point))))
>
> Semi-colons have punctuation syntax, so we're skipping back over the
> entirety of "test;then" instead of stopping after "then".

We should indeed only skip over "then", and then only over ";" and then
only over "test".

> This looks easy enough to fix, but the overall logic of that function is
> somewhat obscure to me, so I've added Stefan to the comments; perhaps he
> has some comments.

The sh syntax is fairly nasty to parse, especially backwards, so I can't
give you any general comment here.  I'd try something and then see if it
breaks any tests (including looking at test/manual/indent/shell.sh).

For sure, I'd recommend adding a regression test.


        Stefan