GNU bug report logs - #73404
30.0.50; [forward/kill/etc]-sexp commands do not behave as expected in tree-sitter modes

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From: Mickey Petersen <mickey <at> masteringemacs.org>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: casouri <at> gmail.com, 73404 <at> debbugs.gnu.org
Subject: bug#73404: 30.0.50; [forward/kill/etc]-sexp commands do not behave as expected in tree-sitter modes
Date: Thu, 26 Sep 2024 16:21:33 +0100

Eli Zaretskii <eliz <at> gnu.org> writes:

>> X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,NO_RECEIVED,
>> 	NO_RELAYS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no
>> 	version=3.4.2
>> From: Mickey Petersen <mickey <at> masteringemacs.org>
>> Cc: casouri <at> gmail.com, 73404 <at> debbugs.gnu.org
>> Date: Thu, 26 Sep 2024 13:13:53 +0100
>>
>>
>> Eli Zaretskii <eliz <at> gnu.org> writes:
>>
>> >   int foo = bar + 2 * baz;
>> >
>> > Suppose you start with point at "foo": what would you expect
>> > forward-sexp to do? nothing?
>> >
>>
>> I expect it to behave as it presently does: default to word-like
>> behaviour such as M-@ / M-f etc.
>
> Then we just lost an opportunity to have more useful commands, because
> we already have M-f and M-@.
>
>> Balanced expression is not well defined, de jure, but it is in
>> practical terms, making it de facto rather well understood and
>> supported. It behaves reasonably consistently across languages, and I
>> use *-sexp commands thousands of times a day in a wide range of major modes and
>> contexts, both in code and also prose.
>
> I think the ability to move by parse sub-trees is also very useful.
>

Agreed. What matters is whether the crop of new sexp commands, such as they
are, perform satisfactorily.

Do you think the examples I listed in the original bug report match
your expectations? If so, then it is probably OK to close the bug report.

>> Most people who use *-sexp (or *-word commands for that matter) in
>> major modes come to recognise how they work and know what happens to
>> the text/point in their buffer before they run them.
>>
>> I would challenge anyone, given even small samples of code, to do the
>> same with the current TS only implementation.
>
> That's just a matter of getting used to the new semantics.
>
>> > I disagree.  Moving by sub-trees is a natural generalization of sexp
>> > movement for languages where parentheses and braces are rare and far
>> > in-between.
>>
>> Yes, if one can intuit the sub trees' structure, which is not so
>> simple; and if the selection of commands are sufficiently expressive
>> enough to let you navigate the tree. I am not sure they are.
>
> There are enough situations where moving by words will also surprise
> you.  For example, did you know that M-f stops when it finds a
> character from a different script?  And yet we still use these
> commands.

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