bug#74507: [PATCH] Indent compounds c-ts-mode when { is not BOL

[Yuan Fu <casouri@gmail.com>]

> On Dec 1, 2024, at 1:51 AM, Jørgen Kvalsvik <j@lambda.is> wrote:
> 
> On 12/1/24 10:25, Yuan Fu wrote:
>>> On Nov 30, 2024, at 12:49 PM, Jørgen Kvalsvik <j@lambda.is> wrote:
>>> 
>>> On 11/30/24 01:16, Yuan Fu wrote:
>>>>> On Nov 29, 2024, at 1:05 AM, Jørgen Kvalsvik <j@lambda.is> wrote:
>>>>> 
>>>>> On 11/29/24 08:57, Eli Zaretskii wrote:
>>>>>>> Cc: theo@thornhill.no,casouri@gmail.com
>>>>>>> From: Jørgen Kvalsvik <j@lambda.is>
>>>>>>> Date: Sun, 24 Nov 2024 10:15:12 +0100
>>>>>>> 
>>>>>>> * lisp/progmodes/c-ts-mode.el (c-ts-mode--parent-is-not-top-compound):
>>>>>>> New function.
>>>>>>> (c-ts-mode--indent-styles): Use it.
>>>>>>> * test/lisp/progmodes/c-ts-mode-resources/indent.erts: New compound
>>>>>>> statement test.
>>>>>> Please make sure the lines here are not too long (see CONTRIBUTE for
>>>>>> details).
>>>>>>> +(defun c-ts-mode--parent-is-not-top-compound (_n parent &rest _)
>>>>>>> +  "Matches when PARENT is not the top level compound statement,
>>>>>>> +the {} that immediately follows the signature."
>>>>>> The first line of a doc string should be a single complete sentence.
>>>>>> Thanks.
>>>>> 
>>>>> Ok. Yuan, would you like me to submit a revision?
>>>> Since your assignment is already done, let’s just apply your patch, and I’ll rebase my changes on top of yours. So yeah, do send the revision patch, thanks!
>>>> Yuan
>>> 
>>> Certainly - I posted it on the bug tracker.
>> Thanks Jørgen. What did you use to generate the patch? For some reason I can’t apply it. My git skill isn’t that great so it could be my problem. If you can apply it fine maybe you can share the command you used?
> 
> I used git format-patch HEAD~1, and I just tested applying it to master with `git am 0001-Indent-compounds-in-c-ts-mode-when-is-not-BOL.patch' which worked.
> 
>> BTW, the commit title is missing. When you add the title, you can also add the bug number. For example:
>> Improve c-ts-mode indentation for macros (bug#74507)
>> Yuan
> 
> Sure. I've attached a new patch with the bug in it. I tested it and it applies cleanly with `git am 0001-Improve-c-ts-mode-compound-indents-bug-74507.patch'
> <0001-Improve-c-ts-mode-compound-indents-bug-74507.patch>

Thanks. This patch applied without a problem. 

I reworked your heuristic into a function rule for better organization, and changed the condition slightly:

(defun c-ts-mode--macro-heuristic-rules (node parent &rest _)
  "Heuristic indent rule for control flow macros.

Eg,

    #define IOTA(var, n) for (int var = 0; var != (n); ++var)

    int main()
    {
      IOTA (v, 10) {
        printf(\"%d \", v);   <-- Here we want to indent
        counter++;            <-- Use baseline rule to align
    }                             to prev sibling

Checked by \"Compound Statement after code (Bug#74507)\" test.

NODE and PARENT are the same as other indent rules."
  (when (and (treesit-node-match-p parent "compound_statement")
             (treesit-node-match-p (treesit-node-prev-sibling parent)
                                   "expression_statement"))
    (let ((parent-bol
           (lambda () (save-excursion
                        (goto-char (treesit-node-start parent))
                        (back-to-indentation)
                        (point)))))
      (cond
       ;; Closing brace.
       ((treesit-node-match-p node "}")
        (cons (funcall parent-bol) 0))
       ;; First sibling.
       ((treesit-node-eq (treesit-node-child parent 0 'named) node)
        (cons (funcall parent-bol)
              c-ts-mode-indent-offset))))))

Instead of checking whether PARENT is top-level compound_statement, I make it check whether the previous sibling is an expression_statement. This way the heuristic works when the macro isn’t at top-level too. Here’s the updated test:

#define IOTA(var, n) for (int var = 0; var != (n); ++var)
int main()
{
  IOTA (v, 10) {
    printf("%d ", v);
  }

  const char *msg = "Hello, world!"; {
    puts("Hello, world!");
  }

  for (int i = 0;
       i < 10;
       i++) {
    IOTA (v, 10) {
      printf("%d ", v);
    }
  }

  {
    IOTA (v, 10) {
      printf("%d ", v);
    }
  }
}

The only test case that doesn’t pass right now is this one:

  const char *msg = "Hello, world!"; {
    puts("Hello, world!");
  }

Is this a real use-case?

Yuan