cc-mode: add ‘c-lineup-ternary-bodies’ (bug#41061)

Introduce ‘c-lineup-ternary-bodies’ function which, when used as
a c lineup function, aligns question mark and colon of a ternary
operator.  For example:

    return arg % 2 == 0 ? arg / 2
                        : (3 * arg + 1);

* lisp/progmodes/cc-align.el (c-lineup-ternary-bodies): New function.
* doc/misc/cc-mode.texi (Operator Line-Up Functions): Document the
new function.
* test/lisp/progmodes/cc-mode-tests.el (c-lineup-ternary-bodies): New
test case.

1 files changed, 21 insertions, 0 deletions

diff --git a/test/lisp/progmodes/cc-mode-tests.el b/test/lisp/progmodes/cc-mode-tests.el
index 0729841ce6f..ad7a52b40d9 100644
--- a/test/lisp/progmodes/cc-mode-tests.el
+++ b/test/lisp/progmodes/cc-mode-tests.el
@@ -78,4 +78,25 @@
       (insert macro-string)
       (c-mode))))
 
+(ert-deftest c-lineup-ternary-bodies ()
+  "Test for c-lineup-ternary-bodies function"
+  (with-temp-buffer
+    (c-mode)
+    (let* ((common-prefix "int value = condition ")
+           (expected-column (length common-prefix)))
+      (dolist (test '(("? a : \n b" . nil)
+                      ("? a \n ::b" . nil)
+                      ("a \n : b" . nil)
+                      ("? a \n : b" . t)
+                      ("? ::a \n : b" . t)
+                      ("? (p ? q : r) \n : b" . t)
+                      ("? p ?: q \n : b" . t)
+                      ("? p ? : q \n : b" . t)
+                      ("? p ? q : r \n : b" . t)))
+        (delete-region (point-min) (point-max))
+        (insert common-prefix (car test))
+        (should (equal
+                 (and (cdr test) (vector expected-column))
+                 (c-lineup-ternary-bodies '(statement-cont . 1))))))))
+
 ;;; cc-mode-tests.el ends here