(internal--get-default-lexical-binding): Be more failsafe

* lisp/files.el (internal--get-default-lexical-binding): Try and
avoid signaling an error.  Make it easier to suppress the
warning for a specific file.

1 files changed, 22 insertions, 15 deletions

diff --git a/lisp/files.el b/lisp/files.el
index 845168121c8..ad6047bd02d 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -4290,24 +4290,31 @@ all the specified local variables, but ignores any settings of \"mode:\"."
                              load-file-name))
                    from
                  (abbreviate-file-name load-file-name))))
-          (display-warning
-           '(files missing-lexbind-cookie)
-           (format-message "Missing `lexical-binding' cookie in %S.
+          (condition-case nil
+              (display-warning
+               `(files missing-lexbind-cookie
+                       ,(if (bufferp source) 'eval-buffer source))
+               (format-message "Missing `lexical-binding' cookie in %S.
 You can add one with `M-x %s RET'.
 See `%s' and `%s'
 for more information."
-                           source
-                           (buttonize "elisp-enable-lexical-binding"
-                                      (lambda (_)
-                                        (pop-to-buffer
-                                         (if (bufferp source) source
-                                           (find-file-noselect source)))
-                                        (call-interactively
-                                         #'elisp-enable-lexical-binding))
-                                      nil "mouse-2: Add cookie")
-                           (funcall mib "(elisp)Selecting Lisp Dialect")
-                           (funcall mib "(elisp)Converting to Lexical Binding"))
-           :warning)))
+                               source
+                               (buttonize "elisp-enable-lexical-binding"
+                                          (lambda (_)
+                                            (pop-to-buffer
+                                             (if (bufferp source) source
+                                               (find-file-noselect source)))
+                                            (call-interactively
+                                             #'elisp-enable-lexical-binding))
+                                          nil "mouse-2: Add cookie")
+                               (funcall mib "(elisp)Selecting Lisp Dialect")
+                               (funcall mib "(elisp)Converting to Lexical Binding"))
+               :warning)
+            ;; In various corner-case situations, `display-warning' may
+            ;; fail (e.g. not yet defined, or can't be (auto)loaded),
+            ;; so use a simple fallback that won't get in the way.
+            (error
+             (message "Missing `lexical-binding' cookie in %S" source)))))
     (default-toplevel-value 'lexical-binding)))
 
 (setq internal--get-default-lexical-binding-function