Re: !(.pattern) can match . and .. if dotglob is enabled

[Nora Platiel]

On 2021-06-15 09:43 Chet Ramey wrote:
> I can see how this would be more intuitive. Let's try it. I'll put support
> in the next devel branch push.

Thanks!

> I'm leaning towards a general statement about how dotglob affects the set
> of filenames that are tested against the extended patterns, rather than
> calling out `!' specially.

What about this:
| The extended pattern matching operators cannot match the leading dot of
| filenames `.' and `..' (or any filename, if dotglob is unset) unless the
| _matching_ subpattern starts with a literal dot.

The important part is "the matching subpattern" (not any subpattern).
If there is no matching subpattern, or if the matching subpattern doesn't start 
with dot, then `.' and `..' are excluded (or all dot files, if dotglob is 
unset).

E.g. both patterns `@(?|.foo*)' and `!(.foo*)', cannot match filename `.' 
because 1) the matching subpattern (`?') doesn't start with dot; 2) there is no 
matching subpattern.

To further clarify we could also expand the definition of `!()' with something 
along these lines:

| !(pattern-list)
|    Matches anything except one of the given patterns.
|+   where anything is whatever `*' can expand to.

The other operators don't have a notion of "anything except" so they don't need 
clarification. This is not a special case, just a consequence of the first 
statement.

Regards,
NP