handle package-version safely to prevent listp error

[yaaama]

When package-version' is not what we expect (e.g a simple string), a listp` error is thrown and you are unable to view the variable documentation due to it. This now handles it and provides a fallback value.

This was a recurring problem I was facing when opening which-key variables using helpful.
which-key would send a value of "31.0" and then cause this error:

helpful--version-info: Wrong type argument: listp, "1.0"

[elken]

I just hit this also and fixed it like this, which I think is preferable as it still shows the package

diff --git a/helpful.el b/helpful.el
index b9ee878..0e73383 100644
--- a/helpful.el
+++ b/helpful.el
@@ -1309,20 +1309,26 @@
   "If SYM has version information, format and return it.
 Return nil otherwise."
   (when (symbolp sym)
-    (let ((package-version
-           (get sym 'custom-package-version))
-          (emacs-version
-           (get sym 'custom-version)))
-      (cond
-       (package-version
-        (format
-         "This variable was added, or its default value changed, in %s version %s."
-         (car package-version)
-         (cdr package-version)))
-       (emacs-version
-        (format
+    (string-join
+     (list
+      (when-let* ((package-version
+		   (get sym 'custom-package-version)))
+	(pcase-let ((`(,package . ,version) (if (listp package-version)
+						package-version
+					      `(,(file-name-base
+						  (symbol-file sym))
+						.
+						,package-version))))
+	  (format
+           "This variable was added, or its default value changed, in %s version %s."
+           package
+           version)))
+      (when-let* ((emacs-version
+		   (get sym 'custom-version)))
+	(format
          "This variable was added, or its default value changed, in Emacs %s."
-         emacs-version))))))
+         emacs-version)))
+     "\n\n")))
 
 (defun helpful--library-path (library-name)
   "Find the absolute path for the source of LIBRARY-NAME.

So feel free to use that instead of "unknown" for a nicer UX if you want

[LemonBreezes]

Please merge some version of this fix someone.

[yaaama]

Please merge some version of this fix someone.

I've merged elkens fix into my master branch

[Wilfred]

Thanks :)