Hyperlink symbol names without word syntax in Help

* lisp/emacs-lisp/lisp-mode.el (lisp-el-font-lock-keywords-2)
(lisp-cl-font-lock-keywords-2): Allow single-character symbol names.
* lisp/help-mode.el (help-xref-symbol-regexp): Also match symbol
names starting with symbol syntax (bug#6601, bug#24309).
* test/lisp/help-mode-tests.el (help-mode-tests-xref-button): Test
hyperlink creation for function names without symbol syntax.

3 files changed, 16 insertions, 14 deletions

diff --git a/lisp/emacs-lisp/lisp-mode.el b/lisp/emacs-lisp/lisp-mode.el
index 1ae216c1a27..8780c5dcd30 100644
--- a/lisp/emacs-lisp/lisp-mode.el
+++ b/lisp/emacs-lisp/lisp-mode.el
@@ -456,8 +456,7 @@ This will generate compile-time constants from BINDINGS."
          ("\\(\\\\\\)\\([^\"\\]\\)"
           (1 (elisp--font-lock-backslash) prepend))
          ;; Words inside ‘’ and `' tend to be symbol names.
-         (,(concat "[`‘]\\(\\(?:\\sw\\|\\s_\\|\\\\.\\)"
-                   lisp-mode-symbol-regexp "\\)['’]")
+         (,(concat "[`‘]\\(" lisp-mode-symbol-regexp "\\)['’]")
           (1 font-lock-constant-face prepend))
          ;; Constant values.
          (,(concat "\\_<:" lisp-mode-symbol-regexp "\\_>")
@@ -507,8 +506,7 @@ This will generate compile-time constants from BINDINGS."
          (,(concat "(" cl-errs-re "\\_>")
            (1 font-lock-warning-face))
          ;; Words inside ‘’ and `' tend to be symbol names.
-         (,(concat "[`‘]\\(\\(?:\\sw\\|\\s_\\|\\\\.\\)"
-                   lisp-mode-symbol-regexp "\\)['’]")
+         (,(concat "[`‘]\\(" lisp-mode-symbol-regexp "\\)['’]")
           (1 font-lock-constant-face prepend))
          ;; Uninterned symbols, e.g., (defpackage #:my-package ...)
          ;; must come before keywords below to have effect
diff --git a/lisp/help-mode.el b/lisp/help-mode.el
index cd08b2b2ba4..7043f12c9a3 100644
--- a/lisp/help-mode.el
+++ b/lisp/help-mode.el
@@ -357,8 +357,7 @@ Commands:
                     "\\(symbol\\|program\\|property\\)\\|" ; Don't link
                     "\\(source \\(?:code \\)?\\(?:of\\|for\\)\\)\\)"
                     "[ \t\n]+\\)?"
-                    ;; Note starting with word-syntax character:
-                    "['`‘]\\(\\sw\\(\\sw\\|\\s_\\)+\\|`\\)['’]"))
+                    "['`‘]\\(\\(?:\\sw\\|\\s_\\)+\\|`\\)['’]"))
   "Regexp matching doc string references to symbols.
 
 The words preceding the quoted symbol can be used in doc strings to
diff --git a/test/lisp/help-mode-tests.el b/test/lisp/help-mode-tests.el
index e0e82c9cc1a..43db59d4b1b 100644
--- a/test/lisp/help-mode-tests.el
+++ b/test/lisp/help-mode-tests.el
@@ -72,14 +72,19 @@ Lisp concepts such as car, cdr, cons cell and list.")
                   #'info)))))
 
 (ert-deftest help-mode-tests-xref-button ()
-  (with-temp-buffer
-    (insert "See also the function ‘interactive’.")
-    (string-match help-xref-symbol-regexp (buffer-string))
-    (help-xref-button 8 'help-function)
-    (should-not (button-at 22))
-    (should-not (button-at 35))
-    (let ((button (button-at 30)))
-      (should (eq (button-type button) 'help-function)))))
+  (let* ((fmt "See also the function ‘%s’.")
+         ;; 1+ translates string index to buffer position.
+         (beg (1+ (string-search "%" fmt))))
+    (with-temp-buffer
+      (dolist (fn '(interactive \` = + - * / %))
+        (erase-buffer)
+        (insert (format fmt fn))
+        (goto-char (point-min))
+        (re-search-forward help-xref-symbol-regexp)
+        (help-xref-button 8 'help-function)
+        (should-not (button-at (1- beg)))
+        (should-not (button-at (+ beg (length (symbol-name fn)))))
+        (should (eq (button-type (button-at beg)) 'help-function))))))
 
 (ert-deftest help-mode-tests-insert-xref-button ()
   (with-temp-buffer