[PATCH 2/3] emacs: allow opting out of notmuch's address completion

[Jonas Bernoulli <jonas@bernoul.li>]

IMO Notmuch should not override the default completion mechanism by
default, at least not globally. But since users are already used to
this behavior it is probably too late to change it. Do the next best
thing and at least allow users to opt out.
---
 emacs/notmuch-address.el | 48 +++++++++++++++++++++++-----------------
 1 file changed, 28 insertions(+), 20 deletions(-)

diff --git a/emacs/notmuch-address.el b/emacs/notmuch-address.el
index 3518beef..6e29b99a 100644
--- a/emacs/notmuch-address.el
+++ b/emacs/notmuch-address.el
@@ -52,21 +52,28 @@ (defun notmuch-address--harvest-ready ()
 (defcustom notmuch-address-command 'internal
   "Determines how address completion candidates are generated.
 
-If it is a string then that string should be an external program
-which must take a single argument (searched string) and output a
-list of completion candidates, one per line.
-
-Alternatively, it can be the symbol `internal', in which case
-internal completion is used; the variable
-`notmuch-address-internal-completion' can be used to customize
-this case.
-
-Finally, if this variable is nil then address completion is
-disabled."
+If this is a string, then that string should be an external
+program, which must take a single argument (searched string)
+and output a list of completion candidates, one per line.
+
+If this is the symbol `internal', then an implementation is used
+that relies on the \"notmuch address\" command, but does not use
+any third-party (i.e. \"external\") programs.
+
+If this is the symbol `as-is', then Notmuch does not modify the
+value of `message-completion-alist'. This option has to be set to
+this value before `notmuch' is loaded, otherwise the modification
+to `message-completion-alist' may already have taken place. This
+setting obviously does not prevent `message-completion-alist'
+from being modified at all; the user or some third-party package
+may still modify it.
+
+Finally, if this is nil, then address completion is disabled."
   :type '(radio
-	  (const :tag "Use internal address completion" internal)
-	  (const :tag "Disable address completion" nil)
-	  (string :tag "Use external completion command"))
+	  (const  :tag "Use internal address completion" internal)
+	  (string :tag "Use external completion command")
+	  (const  :tag "Disable address completion" nil)
+	  (const  :tag "Use default or third-party mechanism" as-is))
   :group 'notmuch-send
   :group 'notmuch-address
   :group 'notmuch-external)
@@ -156,12 +163,13 @@ (defcustom notmuch-address-use-company t
   :group 'notmuch-address)
 
 (defun notmuch-address-setup ()
-  (when (and notmuch-address-use-company
-	     (require 'company nil t))
-    (notmuch-company-setup))
-  (cl-pushnew (cons notmuch-address-completion-headers-regexp
-		    #'notmuch-address-expand-name)
-	      message-completion-alist :test #'equal))
+  (unless (eq notmuch-address-command 'as-is)
+    (when (and notmuch-address-use-company
+	       (require 'company nil t))
+      (notmuch-company-setup))
+    (cl-pushnew (cons notmuch-address-completion-headers-regexp
+		      #'notmuch-address-expand-name)
+		message-completion-alist :test #'equal)))
 
 (defun notmuch-address-toggle-internal-completion ()
   "Toggle use of internal completion for current buffer.
-- 
2.29.1