msmtp: add new option to delegate use to msmtpq

Add option `programs.msmtp.offlineSupport` which when enabled delegates
the usage of `msmtp` to `msmtpq` script. This is achieved by an internal
option `msmtpCommand` which should be called when `msmtp` is used by
another module.

Author: octvs

modules/programs/aerc/accounts.nix

@@ -243,7 +243,7 @@ in
           // optPwCmd "outgoing" passwordCommand;
 
         msmtp = cfg: {
-          outgoing = "msmtpq --read-envelope-from --read-recipients";
+          outgoing = "${config.msmtp.msmtpCommand} --read-envelope-from --read-recipients";
         };
 
       };

modules/programs/alot/accounts.nix

@@ -58,7 +58,10 @@ in
 
   config = lib.mkIf config.notmuch.enable {
     alot.sendMailCommand = lib.mkOptionDefault (
-      if config.msmtp.enable then "msmtpq --read-envelope-from --read-recipients" else null
+      if config.msmtp.enable then
+        "${config.msmtp.msmtpCommand} --read-envelope-from --read-recipients"
+      else
+        null
     );
   };
 }

modules/programs/astroid/accounts.nix

@@ -26,7 +26,7 @@
 
   config = lib.mkIf config.notmuch.enable {
     astroid.sendMailCommand = lib.mkIf config.msmtp.enable (
-      lib.mkOptionDefault "msmtpq --read-envelope-from --read-recipients"
+      lib.mkOptionDefault "${config.msmtp.msmtpCommand} --read-envelope-from --read-recipients"
     );
   };
 }

modules/programs/msmtp/default.nix

@@ -52,7 +52,7 @@ in
 {
 
   options = {
-    programs.msmtp = {
+    programs.msmtp = rec {
       enable = lib.mkEnableOption "msmtp";
 
       package = lib.mkPackageOption pkgs "msmtp" { };
@@ -114,6 +114,23 @@ in
           See <https://marlam.de/msmtp/msmtprc.txt> for examples.
         '';
       };
+
+      msmtpCommand = mkOption {
+        type = types.package;
+        internal = true;
+        readOnly = true;
+        default = if offlineSupport then "${pkgs.msmtp}/bin/msmtpq" else "${pkgs.msmtp}/bin/msmtp";
+      };
+
+      offlineSupport = lib.mkOption {
+        type = types.bool;
+        default = true;
+        description = ''
+          Use msmtpq script instead of msmtp. The script allows an offline
+          first workflow by adding all mails to a queue regardless of the
+          network status, and flushing them later.
+        '';
+      };
     };
 
     accounts.email.accounts = mkOption {
@@ -135,7 +152,7 @@ in
           (lib.mkIf (cfg.extraAccounts != "") (lib.mkAfter cfg.extraAccounts))
         ];
 
-        home.sessionVariables = {
+        home.sessionVariables = lib.optionalAttrs cfg.offlineSupport {
           MSMTPQ_Q = "${config.xdg.dataHome}/msmtp/queue";
           MSMTPQ_LOG = "${config.xdg.dataHome}/msmtp/queue.log";
         };

modules/programs/neomutt/accounts.nix

@@ -61,7 +61,11 @@ in
 
     sendMailCommand = mkOption {
       type = types.nullOr types.str;
-      default = if config.msmtp.enable then "msmtpq --read-envelope-from --read-recipients" else null;
+      default =
+        if config.msmtp.enable then
+          "${config.msmtp.msmtpCommand} --read-envelope-from --read-recipients"
+        else
+          null;
       defaultText = lib.literalExpression ''
         if config.msmtp.enable then
           "msmtpq --read-envelope-from --read-recipients"