mu4e: implement context-policies

Allow setting a policy about what context to choose when starting mu4e
and composing a message. Basically:

When you have defined contexts and you start mu4e it decides which
context to use based on the variable `mu4e-context-policy';
similarly, when you compose a new message, the context is determined
using `mu4e-compose-context-policy'.

These policies can be one of the following:
- a symbol always-ask: unconditionally ask the user what context to pick

The other choices only apply if none of the context matches (i.e., if
none of the contexts' match-functions returns t:

- symbol ask: ask the user
- a symbol pick-first: pick the first context
- nil: don't change the context

mu4e/mu4e-compose.el

@@ -112,12 +112,34 @@ for example:
 
 The various `message-' functions from `message-mode' are available
 for querying the message information."
-    :type '(choice (const :tag "move message to mu4e-sent-folder" sent)
+  :type '(choice (const :tag "move message to mu4e-sent-folder" sent)
-		 (const :tag "move message to mu4e-trash-folder" trash)
+	   (const :tag "move message to mu4e-trash-folder" trash)
-		 (const :tag "delete message" delete))
+	   (const :tag "delete message" delete))
   :safe 'symbolp
   :group 'mu4e-compose)
 
+
+(defcustom mu4e-compose-context-policy nil
+  "Determines how mu4e should determine the context when composing a new message.
+
+If POLICY is
+'always-ask, we ask the user unconditionally.
+
+In all other cases, if any context matches (using its match
+function), this context is returned. If none of the contexts
+match, POLICY determines what to do:
+
+- pick-first: pick the first of the contexts available
+- ask: ask the user
+- otherwise, return nil. Effectively, this leaves the current context in place."
+  :type '(choice
+	   (const :tag "Always ask what context to use" 'always-ask)
+	   (const :tag "Ask if none of the contexts match" 'ask)
+	   (const :tag "Pick the default (first) context if none match" 'pick-first)
+	   (const :tag "Don't change the context when none match" nil)
+  :safe 'symbolp
+  :group 'mu4e-compose))
+
 (defcustom mu4e-compose-pre-hook nil
   "Hook run just *before* message composition starts.
 If the compose-type is either 'reply' or 'forward', the variable
@@ -370,10 +392,9 @@ tempfile)."
   ;; message being forwarded or replied to, otherwise it is nil.
   (set (make-local-variable 'mu4e-compose-parent-message) original-msg)
   (put 'mu4e-compose-parent-message 'permanent-local t)
-  (let ((context (mu4e-context-determine mu4e-compose-parent-message)))
+  ;; maybe switch the context
-    (if context
+  (mu4e~context-autoswitch mu4e-compose-parent-message
-      (mu4e-context-switch nil (mu4e-context-name context))
+			   mu4e-compose-context-policy)
-      (when mu4e-contexts (mu4e-context-switch nil))))
   (run-hooks 'mu4e-compose-pre-hook)
 
   ;; this opens (or re-opens) a messages with all the basic headers set.

mu4e/mu4e-context.el

@@ -100,13 +100,13 @@ non-nil."
       (mu4e-message "Switched context to %s" (mu4e-context-name context)))
     context))
 
-(defun mu4e-context-autoselect ()
+(defun mu4e~context-autoswitch (&optional msg policy)
   "When contexts are defined but there is no context yet, switch
 to the first whose :match-func return non-nil. If none of them
-match, return the first."
+match, return the first. For MSG and POLICY, see `mu4e-context-determine'."
- (when (and mu4e-contexts (not (mu4e-context-current)))
+  (when mu4e-contexts
-   (mu4e-context-switch
+    (let ((context (mu4e-context-determine msg policy)))
-     (mu4e-context-name  (mu4e-context-determine nil 'pick-first)))))
+      (when context (mu4e-context-switch (mu4e-context-name context))))))
 
 (defun mu4e-context-determine (msg &optional policy)
   "Return the first context with a match-func that returns t. MSG
@@ -114,20 +114,27 @@ points to the plist for the message replied to or forwarded, or
 nil if there is no such MSG; similar to what
 `mu4e-compose-pre-hook' does.
 
-POLICY determines what to do if there are contexts but none match. The following
+POLICY specifies how to do the determination. If POLICY is
-are supported:
+'always-ask, we ask the user unconditionally.
+
+In all other cases, if any context matches (using its match
+function), this context is returned. If none of the contexts
+match, POLICY determines what to do:
+
 - pick-first: pick the first of the contexts available
 - ask: ask the user
 - otherwise, return nil. Effectively, this leaves the current context in place."
   (when mu4e-contexts
-    (or (find-if (lambda (context)
+    (if (eq policy 'always-ask)
-		   (and (mu4e-context-match-func context)
+      (mu4e~context-ask-user "Select context: ")
-		     (funcall (mu4e-context-match-func context) msg))) mu4e-contexts)
+      (or (find-if (lambda (context)
-      ;; no context found
+		     (and (mu4e-context-match-func context)
-      (case policy
+		       (funcall (mu4e-context-match-func context) msg))) mu4e-contexts)
-	(pick-first (car mu4e-contexts))
+	;; no context found
-	(ask (mu4e~context-ask-user "Select context: "))
+	(case policy
-	(otherwise nil)))))
+	  (pick-first (car mu4e-contexts))
+	  (ask (mu4e~context-ask-user "Select context: "))
+	  (otherwise nil))))))
 
 (provide 'mu4e-context)
  

mu4e/mu4e-utils.el

@@ -46,7 +46,7 @@
 (declare-function mu4e~proc-mkdir     "mu4e-proc")
 (declare-function mu4e~proc-running-p "mu4e-proc")
 
-(declare-function mu4e-context-autoselect  "mu4e-context")
+(declare-function mu4e~context-autoswitch  "mu4e-context")
 
 (declare-function show-all "org")
 
@@ -737,9 +737,9 @@ first.
 If mu4e is already running, execute function FUNC (if non-nil).
 Otherwise, check various requirements, then start mu4e. When
 successful, call FUNC (if non-nil) afterwards."
-
+  ;; maybe switch the context
-  ;; auto-select some account
+  (mu4e~context-autoswitch mu4e-compose-parent-message
-  (mu4e-context-autoselect)
+  mu4e-compose-context-policy)
   ;; if we're already running, simply go to the main view
   (if (mu4e-running-p)   ;; already running?
     (when func                 ;; yes! run func if defined

mu4e/mu4e-vars.el

@@ -114,7 +114,6 @@ better with e.g. offlineimap."
   :group 'mu4e
   :safe 'booleanp)
 
-
 (defcustom mu4e-attachment-dir (expand-file-name "~/")
   "Default directory for saving attachments.
 This can be either a string (a file system path), or a function
@@ -218,6 +217,29 @@ Suggested possible values are:
   :options '(completing-read ido-completing-read)
   :group 'mu4e)
 
+(defcustom mu4e-context-policy 'ask
+  "Determines how mu4e should determine the context when starting up.
+
+If POLICY is 'always-ask, we ask the user unconditionally.
+
+In all other cases, if any context matches (using its match
+function), this context is returned. If none of the contexts
+match, POLICY determines what to do:
+
+- pick-first: pick the first of the contexts available
+- ask: ask the user
+- otherwise, return nil. Effectively, this leaves the current context in place.
+
+Also see `mu4e-compose-context-policy'."
+  :type '(choice
+	   (const :tag "Always ask what context to use" 'always-ask)
+	   (const :tag "Ask if none of the contexts match" 'ask)
+	   (const :tag "Pick the default (first) context if none match" 'pick-first)
+	   (const :tag "Don't change the context when none match" nil)
+  :safe 'symbolp
+  :group 'mu4e))
+
+
 ;; crypto
 (defgroup mu4e-crypto nil
   "Crypto-related settings."

mu4e/mu4e.texi

@@ -37,7 +37,7 @@ Documentation License.''
 
 @dircategory Emacs
 @direntry
-* mu4e: (mu4e).        An email client for Emacs.
+* mu4e: (Mu4e).        An email client for GNU/Emacs.
 @end direntry
 
 @contents
@@ -1990,8 +1990,8 @@ also match this extra search pattern. @key{\} takes you back to the previous
 query, so, effectively 'widens' the search. Technically, narrowing the results
 of query @t{x} with expression @t{y} implies doing a search @t{(x) AND y}.
 
-Note, messages that were not in your in your original search results because
+Note that messages that were not in your original search results because
-of @code{mu4e-headers-results-limit}, may show up in the narrowed query.
+of @code{mu4e-headers-results-limit} may show up in the narrowed query.
 
 @subsection Including related messages
 @anchor{Including related messages}
@@ -2256,16 +2256,15 @@ example:
 
 @menu
 * Defining a context::
-* Default context::
+* Context policies::
 * Contexts example::
-* Contexts notes::
 * Some context tricks::
 @end menu
 
 It can be useful to be able to switch between different sets of settings
 in @t{mu4e}; typical examples include the case where you have different
 e-mail accounts for private and work email, each with their own settings
-for e-mail addresses, mailservers etc.
+for folders, e-mail addresses, mailservers etc.
 
 The @code{mu4e-context} system is a @t{mu4e}-specific mechanism to allow
 for that; users can be define different contexts, and either manually
@@ -2307,19 +2306,34 @@ an alist of variable settings for this account.
 @t{mu4e} uses a variable @code{mu4e-contexts}, which is a list of such
 objects.
 
-@node Default context
+@node Context policies
-@section Default context
+@section Context policies
 
-When you have defined contexts and you start @t{mu4e}, it automatically
+When you have defined contexts and you start @t{mu4e} it decides which
-switches to the first context whose @code{match-func} returns
+context to use based on the variable @code{mu4e-context-policy};
-non-nil. If none of them do, it picks the first. So, put your 'default'
+similarly, when you compose a new message, the context is determined
-context as the first in @code{mu4e-contexts}.
+using @code{mu4e-compose-context-policy}.
+
+These policies can be one of the following:
+@itemize
+@item a symbol @t{always-ask}: unconditionally ask the user what context to pick
+@end itemize
+
+The other choices only apply if none of the context matches (i.e., if
+none of the contexts' match-functions returns @code{t}:
+
+@itemize
+@item a symbol @t{ask}: ask the user
+@item a symbol @t{pick-first}: pick the first context
+@item @t{nil}: don't change the context
+@end itemize
 
 @node Contexts example
 @section Example
 
-Let's look at an example; we define two contexts, 'Private' and 'Work'
+Let's explain how contexts work by looking at an example. We define two
-for a fictional user Alice Derleth.
+contexts, 'Private' and 'Work' for a fictional user @emph{Alice
+Derleth}.
 
 Note that in this case, we automatically switch to the first context
 when starting; see the discussion in the previous section.
@@ -2354,16 +2368,13 @@ when starting; see the discussion in the previous section.
 		      "Miskatonic University, Dept. of Occult Sciences\n"))))))
 @end lisp
 
-@node Contexts notes
+A couple of notes about this example:
-@section Context notes
-
-Couple of notes:
 @itemize
 @item You can manually switch the focus use @code{M-x mu4e-context-switch}, by default bound to @kbd{;} in headers, view and main mode.
 The current focus appears in the mode-line.
-@item Normally, @code{M-x mu4e-context-switch} does not call the enter/leave functions if the 'new' context is the same as the old one.
+@item Normally, @code{M-x mu4e-context-switch} does not call the enter or leave functions if the 'new' context is the same as the old one.
-However, with a prefix-argument (@kbd{C-u}), you can force @t{mu4e} to call
+However, with a prefix-argument (@kbd{C-u}), you can force @t{mu4e} to
-those function even in that case.
+invoke those function even in that case.
 @item The function @code{mu4e-context-current} returns the current-context; the current context is also visiable in the mode-line when in
 headers, view or main mode.
 @item You can set any kind of variable; including settings for mail servers etc. However, settings like @code{mu4e-maildir}
@@ -2378,13 +2389,13 @@ context we are entering.
 @node Some context tricks
 @section Some context tricks
 
-
 It is possible to automatically fill @code{mu4e-user-address-list} by
 concatenating the @code{user-mail-address} fields of all contexts:
 
 @lisp
-;; This sets `mu4e-user-mail-address-list' to the concatenation of all `user-mail-address' values
+;; This sets `mu4e-user-mail-address-list' to the concatenation of all
-;; for all contexts. If you have other mail addresses as well, you'll need to add those manually.
+;; `user-mail-address' values for all contexts. If you have other mail
+;; addresses as well, you'll need to add those manually.
 (setq mu4e-user-mail-address-list
       (delq nil
             (mapcar (lambda (context)
@@ -2906,6 +2917,7 @@ two days, you could add this to @code{org-capture-templates}:
 
 If you use the functionality a lot, you may want to define key-bindings
 for that in headers and view mode:
+
 @lisp
 (define-key mu4e-headers-mode-map (kbd "C-c c") 'org-mu4e-store-and-capture)
 (define-key mu4e-view-mode-map    (kbd "C-c c") 'org-mu4e-store-and-capture)