Shorten docstrings generated by cl-defsubst

* lisp/emacs-lisp/cl-macs.el (cl-defsubst): Split the first line of
the docstring into 2 lines if the function name is very long.
Additionally, remove the word "inlining" in the generated docstring as
it is not very useful and increases the likelihood of "docstring wider
than 80 characters" errors.  (Bug#65790)

2 files changed, 19 insertions, 1 deletions

diff --git a/lisp/emacs-lisp/cl-macs.el b/lisp/emacs-lisp/cl-macs.el
index c8e2610c8b0..dc17f992660 100644
--- a/lisp/emacs-lisp/cl-macs.el
+++ b/lisp/emacs-lisp/cl-macs.el
@@ -2931,7 +2931,14 @@ The function's arguments should be treated as immutable.
              ,(if (memq '&key args)
                   `(&whole cl-whole &cl-quote ,@args)
                 (cons '&cl-quote args))
-             ,(format "compiler-macro for inlining `%s'." name)
+             ;; NB.  This will produce incorrect results in some
+             ;; cases, as our coding conventions says that the first
+             ;; line must be a full sentence.  However, if we don't
+             ;; word wrap we will have byte-compiler warnings about
+             ;; overly long docstrings.  So we can't have a perfect
+             ;; result here, and choose to avoid the byte-compiler
+             ;; warnings.
+             ,(internal--format-docstring-line "compiler-macro for `%s'." name)
              (cl--defsubst-expand
               ',argns '(cl-block ,name ,@(cdr (macroexp-parse-body body)))
               nil
diff --git a/test/lisp/emacs-lisp/bytecomp-tests.el b/test/lisp/emacs-lisp/bytecomp-tests.el
index c0adab75269..102616c9bb7 100644
--- a/test/lisp/emacs-lisp/bytecomp-tests.el
+++ b/test/lisp/emacs-lisp/bytecomp-tests.el
@@ -972,6 +972,17 @@ byte-compiled.  Run with dynamic binding."
   (bytecomp--with-warning-test "defvar.*foo.*wider than.*characters"
     `(defvar foo t ,bytecomp-tests--docstring)))
 
+(ert-deftest bytecomp-warn-wide-docstring/cl-defsubst ()
+  (bytecomp--without-warning-test
+   `(cl-defsubst short-name ()
+      "Do something."))
+  (bytecomp--without-warning-test
+   `(cl-defsubst long-name-with-less-80-characters-but-still-quite-a-bit ()
+      "Do something."))
+  (bytecomp--with-warning-test "wider than.*characters"
+   `(cl-defsubst long-name-with-more-than-80-characters-yes-this-is-a-very-long-name-but-why-not!! ()
+      "Do something.")))
+
 (ert-deftest bytecomp-warn-quoted-condition ()
   (bytecomp--with-warning-test
       "Warning: `condition-case' condition should not be quoted: 'arith-error"