bug#59633: 29.0.50; tree-sitter-bash: Incorrect behaviour of heredocs with expansions

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

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Yuan Fu <casouri@gmail.com> writes:

> miha@kamnitnik.top writes:
>
>> 1. Visit empty buffer test in fundamental mode (C-x b test RET)
>> 2. Insert
>>
>> tee << EOF
>> text1 $var
>> text2 $(echo cmd)
>> text3
>> $var2
>> EOF
>>
>> 3. Put point before "text2"
>> 4. M-x load-library RET treesit RET
>> 5. M-: (treesit-node-children (treesit-node-at (point) 'bash))
>>
>>     => (#<treesit-node (simple_expansion) in 18-22>
>>         #<treesit-node (command_substitution) in 29-40>)
>>
>>    Note that this list is incorrect, "$var2" at the end of heredoc is
>>    missing.
>>
>> 6. M-: (treesit-node-first-child-for-pos (treesit-node-at (point) 'bash) (point))
>>
>>    => nil
>>
>>    Expected return value here is #<treesit-node (command_substitution) in 29-40>
>>
>> I'm not sure if this bug is on Emacs, tree-sitter-bash or even
>> tree-sitter itself and I don't know how to check.
>>
>> tree-sitter-bash version: 0.19.0.r19.g77cf8a7-1
>> tree-sitter version: 0.20.7-1
>>
>> Thanks and best regards.
>
> Thanks. This is the tree produced by tree-sitter, does it match your
> expectation?
>
> (heredoc_body
> (simple_expansion $ (variable_name))
> (command_substitution $(
>   (command
>    name: (command_name (word))
>    argument: (word))
>   ))
> (simple_expansion $ (variable_name)))
>
> treesit-node-at gives you the _smallest_ node at point, maybe that’s why
> you didn’t see expected behavior?
>
> Yuan

The latest commit to tree-sitter-bash is

commit 4488aa41406547e478636a4fcfd24f5bbc3f2f74
Author: João P. L. Carvalho <jaopaulolc@gmail.com>
Date:   Sun Nov 27 20:39:41 2022 -0700

    Fix scanning of heredoc_body to allow empty bodies (#137).

Seems like it has fixed the problem described in the 5. step and the
tree produced by tree-sitter is now expected.

The problem in the 6. step is still present though. With point in front
of command_substitution, on would expect

    (treesit-node-first-child-for-pos (treesit-node-at (point) 'bash) (point))

to return the command_substitution node instead of returning nil.

Thanks.

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