From d8204db859a1807a4a48bd9dc89f20ed37b008bb Mon Sep 17 00:00:00 2001
From: =?utf8?q?J=C3=B8rgen=20Kvalsvik?= <j@lambda.is>
Date: Fri, 4 Oct 2024 21:38:33 +0200
Subject: [PATCH] Fix c-ts-mode indentation for initializer lists (bug#73661)

The intentation behavior differed between c-mode/c++-mode
and *-ts-mode for initializer lists where the first element was
not at beginning-of-line.  The anchor-prev-sibling function gave
up and returned nil, but it should (probably) anchor on the
first element in the initializer list, such as this:

return { v1, v2, ...,
         y1, y2, ... };

c-ts-mode behaved better and figured out how to align, but I
added a test for a similar compound literal to prevent
regressions.

* lisp/progmodes/c-ts-mode.el (c-ts-mode--anchor-prev-sibling):
Anchor at first sibling unless bol is found.

* test/lisp/progmodes/c-ts-mode-resources/indent.erts: New
initializer list and compound literal test.

Copyright-paperwork-exempt: yes
(cherry picked from commit e49b479f8692573379a1ee3417bdda9e1f777888)
---
 lisp/progmodes/c-ts-mode.el                   |  9 +++--
 .../progmodes/c-ts-mode-resources/indent.erts | 39 +++++++++++++++++++
 2 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/lisp/progmodes/c-ts-mode.el b/lisp/progmodes/c-ts-mode.el
index 303c994637c..3f6a7422aa0 100644
--- a/lisp/progmodes/c-ts-mode.el
+++ b/lisp/progmodes/c-ts-mode.el
@@ -338,10 +338,13 @@ characters of the current line."
           ;; If the start of the previous sibling isn't at the
           ;; beginning of a line, something's probably not quite
           ;; right, go a step further. (E.g., comment after a
-          ;; statement.)
+          ;; statement.)  If the previous sibling is the first named
+          ;; node then anchor to that, e.g. when returning an aggregate
+          ;; and starting the items on the same line as {.
           (_ (goto-char (treesit-node-start prev-sibling))
-             (if (looking-back (rx bol (* whitespace))
-                               (line-beginning-position))
+             (if (or (looking-back (rx bol (* whitespace))
+                                   (line-beginning-position)))
+                     (null (treesit-node-prev-sibling prev-sibling t))
                  (setq continue nil)
                (setq prev-sibling
                      (treesit-node-prev-sibling prev-sibling)))))))
diff --git a/test/lisp/progmodes/c-ts-mode-resources/indent.erts b/test/lisp/progmodes/c-ts-mode-resources/indent.erts
index 599173832b5..a13a74cf8b3 100644
--- a/test/lisp/progmodes/c-ts-mode-resources/indent.erts
+++ b/test/lisp/progmodes/c-ts-mode-resources/indent.erts
@@ -208,6 +208,21 @@ int main()
 }
 =-=-=
 
+Name: Return Compund Literal
+
+=-=
+struct pair { int fst, snd; };
+struct pair
+make_pair(int long_identifier_a[], int long_identifier_b[],
+	  int offset_a, int offset_b)
+{
+  int base_offset = 10;
+  return (struct pair) { long_identifier_a[base_offset + offset_b],
+                         long_identifier_b[base_offset + offset_b] };
+}
+
+=-=-=
+
 Name: Switch-Case statement
 
 =-=
@@ -486,6 +501,30 @@ namespace A {
 }
 =-=-=
 
+Name: Return Aggregate Initialized Struct
+
+=-=
+struct pair { int x, y; }
+pair
+make_pair(int long_identifier_a[], int long_identifier_b[],
+          int offset_a, int offset_b)
+{
+  int base_offset = 10;
+  return { long_identifier_a[base_offset + offset_b],
+       long_identifier_b[base_offset + offset_b] };
+}
+=-=
+struct pair { int x, y; }
+pair
+make_pair(int long_identifier_a[], int long_identifier_b[],
+          int offset_a, int offset_b)
+{
+  int base_offset = 10;
+  return { long_identifier_a[base_offset + offset_b],
+           long_identifier_b[base_offset + offset_b] };
+}
+=-=-=
+
 Code:
   (lambda ()
     (c-ts-mode)
-- 
2.39.5