Subject: bug#77746: [PATCH] sh-mode: Fix incorrect word syntax for punctuation in sh-mode

From: Stefan Monnier <[email-masked]>
Date: Sun, 13 Apr 2025 13:33:55 -0400

>> In sh and Bash, the characters !%^~:.,= and are not valid in variable or
>> function names.

I'm not positive about all of them, but at least some of those can
appear in the names of commands.

>> Assigning them the "_" syntax causes Emacs to treat them as word
>> constituents,

Not quite: it makes them appear as "symbol constituents".

>> disrupting navigation and completion (e.g. dabbrev-expand,
>> forward-word, etc.).

`forward-word` for example shouldn't be affected (unless you enable
`superword-mode`).  `dabbrev-expand` OTOH is affected, indeed.

>> The attached patch updates the syntax table in sh-mode to mark
>> these characters as punctuation, correcting the issue.
> TBH, such a change sounds scary, as it could cause all kinds of
> unintended changes in behavior.

It's indeed risky/delicate.  The syntax-tables are a fairly crude tool,
so we often need to use different tables at different places.

Rather than go straight to changing the syntax-table, I suggest you
start by providing some concrete examples of behaviors you consider
incorrect with the current code.  Maybe changing the main syntax-table
of that mode will be the better option, but if so, it'll probably
require changing other code to keep using the current
syntax-table there.
[ I haven't tested it, but I'd expect trouble with your patch either in
  font-lock or indentation if you have commands with names like
  `if-config`.  ]

        Stefan