bug#61541: 30.0.50; Wrong indentarion in csharp-mode

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

Ergus <spacibba@aol.com> writes:

> On Fri, Feb 17, 2023 at 10:06:50PM +0100, Jostein Kj�nigsen wrote:
>>2/17/23 20:28, Theodor Thornhill wrote:
>>>Ergus <spacibba@aol.com> writes:
>>>
>>>>Hi:
>>>>
>>>>I just found that this indentations are wrong in csharp mode:
>>>>
>>>>// wrong
>>>>new myNamespace.myClass
>>>>{
>>>>     Name1 = x.Value, // defun-block-intro
>>>>	var2 = 2     // statement-cont
>>>>	}            // statement-cont
>>>>
>>>>
>>>>The problem seems to be related with the dot (.) in the new, because
>>>>this variant indents correctly:
>>>>
>>>>// right
>>>>new myClass
>>>>{
>>>>     Name1 = x.Value,   // brace-list-intro
>>>>     var2 = 2           // brace-list-entry
>>>>}                      // brace-list-close
>>>>
>>>>
>>>>csharp-ts-mode is doing it right BTW.
>>>>
>>>Hi!
>>>
>>>Yeah, this is one of the harder issues iirc, and one of the ones that
>>>made us move to tree-sitter in csharp-mode in the first place.
>>>
>>>What do you think Jostein?
>>>
>>>Patches welcome!
>>>
>>>Theo
>>>
>>First of all: Thanks for a detailed bug-report.
>>
>>Then for the bad news: I may be missing something here. I'm on the 
>>latest revision of the emacs-29 branch, and I really can't reproduce 
>>at all.
>>
>>I've tried typing out the concrete code-samples above, and I've tried 
>>copy-pasting them.
>>
>>No matter what I do, I cannot reproduce the behaviour outlined above.
>>
>>Ergus: Could you come up with a even more complete example?
>>
>>I mean... If I can't reproduce, I definitely won't be able to come up 
>>with a patch.
>>
>>--
>>Jostein
>>
>
> Hi Jostein:
>
> I just do:
>
> emacs -Q /tmp/main.cs
>
> Then pasted (or write) the code snippet shown in the example, and
> re-indent the buffer:
>
> I get this:
>
> new myNamespace.myClass
> {
>      Name1 = 1,
>          Name2 =2
>          }
>
> Exactly like in the example C-c C-o shows the same than in the
> example. Even the fontification is wrong.
>
> If I remove the dot like this myNamespacemyClass the fontification and
> indentation is fixed immediately.
>
> I am using the master branch (emacs-version = 30.0.50) tomorrow I can
> try to reproduce the issue on emacs-29 branch, but I have to build it.
>
> Best,
> Ergus


Try this, Ergus and Jostein. What do you think?

diff --git a/lisp/progmodes/csharp-mode.el b/lisp/progmodes/csharp-mode.el
index b6b842d7fd..293a910081 100644
--- a/lisp/progmodes/csharp-mode.el
+++ b/lisp/progmodes/csharp-mode.el
@@ -474,28 +474,37 @@ csharp-guess-basic-syntax
          (and (eq (char-before) ?\])
               (not (eq (char-after) ?\;))))))
     `((annotation-top-cont ,(c-point 'iopl))))
-
    ((and
      ;; Heuristics to find object initializers
      (save-excursion
        ;; Next non-whitespace character should be '{'
        (goto-char (c-point 'boi))
-       (eq (char-after) ?{))
-     (save-excursion
-       ;; 'new' should be part of the line
-       (goto-char (c-point 'iopl))
-       (looking-at ".*new.*"))
+       (unless (eq (char-after) ?{)
+         (backward-up-list 1 t t))
+       (save-excursion
+         ;; 'new' should be part of the line
+         (goto-char (c-point 'iopl))
+         (looking-at ".*new.*")))
      ;; Line should not already be terminated
      (save-excursion
        (goto-char (c-point 'eopl))
        (or (not (eq (char-before) ?\;))
            (not (eq (char-before) ?\{)))))
-    (if (save-excursion
-          ;; if we have a hanging brace on line before
-          (goto-char (c-point 'eopl))
-          (eq (char-before) ?\{))
-        `((brace-list-intro ,(c-point 'iopl)))
-      `((block-open) (statement ,(c-point 'iopl)))))
+    (cond
+     ((save-excursion
+        ;; if we have a hanging brace on line before
+        (goto-char (c-point 'eopl))
+        (eq (char-before) ?\{))
+      `((brace-list-intro ,(c-point 'iopl))))
+     ((save-excursion
+        ;; if we have a hanging brace on line before
+        (goto-char (c-point 'boi))
+        (and (eq (char-after) ?\})
+             `((brace-list-close ,(save-excursion
+                                    (backward-up-list 1 t t)
+                                    (point)))))))
+     (t
+      `((block-open) (statement ,(c-point 'iopl))))))
    (t
     (apply orig-fun args))))