msmtp: add nonblocking support

pkgs/applications/networking/msmtp/default.nix

@@ -1,11 +1,21 @@
-{ stdenv, lib, fetchurl, autoreconfHook, pkgconfig
+{ stdenv, lib, fetchurl, fetchFromGitHub, autoreconfHook, pkgconfig
 , openssl, netcat-gnu, gnutls, gsasl, libidn, Security
-, systemd ? null }:
+, systemd ? null, eject ? null }:
 
 let
   tester = "n"; # {x| |p|P|n|s}
   journal = if stdenv.isLinux then "y" else "n";
 
+  # preferNonBlock = stdenv.isLinux;
+  preferNonBlock = false;
+
+  nonblock = fetchFromGitHub {
+    owner  = "Stebalien";
+    repo   = "msmtp-queue";
+    rev    = "07032a4e4c8ea0d2364641c959db0c60f52423c7";
+    sha256 = "0g2aph30007spkdwxljrlr2bliivf9nrdis3d3jvjpx8l6k60rr9";
+  };
+
 in stdenv.mkDerivation rec {
   name = "msmtp-${version}";
   version = "1.6.6";
@@ -20,13 +30,17 @@ in stdenv.mkDerivation rec {
   ];
 
   buildInputs = [ openssl gnutls gsasl libidn ]
-    ++ stdenv.lib.optional stdenv.isDarwin Security;
+    ++ lib.optional stdenv.isDarwin Security
+    ++ lib.optionals preferNonBlock [ nonblock eject ];
   nativeBuildInputs = [ autoreconfHook pkgconfig ];
 
+  enableParallelBuilding = true;
+
   configureFlags =
     stdenv.lib.optional stdenv.isDarwin [ "--with-macosx-keyring" ];
 
   postInstall = ''
+    ${lib.optionalString (!preferNonBlock) ''
     substitute scripts/msmtpq/msmtpq $out/bin/msmtpq \
       --replace @msmtp@      $out/bin/msmtp \
       --replace @nc@         ${netcat-gnu}/bin/nc \
@@ -36,6 +50,23 @@ in stdenv.mkDerivation rec {
 
     substitute scripts/msmtpq/msmtp-queue $out/bin/msmtp-queue \
       --replace @msmtpq@ $out/bin/msmtpq
+    ''}
+    ${lib.optionalString preferNonBlock ''
+    mkdir -p $out/lib/systemd/user
+    cp ${nonblock}/msmtp* $out/bin/
+    cp ${nonblock}/systemd/* $out/lib/systemd/user
+    for f in $out/bin/msmtpq* ; do
+      sed $f -i -r \
+        -e 's|^QUEUE_DIR.*|QUEUE_DIR="''${MSMTP_QUEUE:-''${XDG_DATA_HOME:-$HOME/.local/share}/mail.queue}"|' \
+        -e 's|^CONFIG.*|CONFIG="''${XDG_CONFIG_HOME:-$HOME/.config}/msmtprc"|' \
+        -e 's| flock | ${eject}/bin/flock |'
+    done
+    for f in $out/lib/systemd/user/* ; do
+      substituteInPlace $f \
+        --replace /usr/local               $out \
+        --replace .local/share/mail.queue  .cache/msmtp/queue
+    done
+    ''}
 
     chmod +x $out/bin/*
   '';