slack: add MacOS target

pkgs/applications/networking/instant-messengers/slack/default.nix

@@ -8,6 +8,33 @@ let
 
   version = "4.2.0";
 
+  inherit (stdenv.hostPlatform) system;
+
+  throwSystem = throw "Unsupported system: ${system}";
+
+  pname = "slack";
+
+  sha256 = {
+    x86_64-darwin = "0947a98m7yz4hldjvcqnv9s17dpvlsk9sflc1zc99hf500zck0w1";
+    x86_64-linux = "01b2klhky04fijdqcpfafgdqx2c5nh2fpnzvzgvz10hv7h16cinv";
+  }.${system} or throwSystem;
+
+
+  meta = with stdenv.lib; {
+    description = "Desktop client for Slack";
+    homepage = https://slack.com;
+    license = licenses.unfree;
+    maintainers = [ maintainers.mmahut ];
+    platforms = [ "x86_64-darwin" "x86_64-linux" ];
+  };
+
+  linux = stdenv.mkDerivation rec {
+    inherit pname version meta;
+    src = fetchurl {
+      url = "https://downloads.slack-edge.com/linux_releases/slack-desktop-${version}-amd64.deb";
+      inherit sha256;
+    };
+
     rpath = stdenv.lib.makeLibraryPath [
       alsaLib
       at-spi2-atk
@@ -49,21 +76,6 @@ let
       xorg.libXScrnSaver
     ] + ":${stdenv.cc.cc.lib}/lib64";
 
-  src =
-    if stdenv.hostPlatform.system == "x86_64-linux" then
-      fetchurl {
-        url = "https://downloads.slack-edge.com/linux_releases/slack-desktop-${version}-amd64.deb";
-        sha256 = "01b2klhky04fijdqcpfafgdqx2c5nh2fpnzvzgvz10hv7h16cinv";
-      }
-    else
-      throw "Slack is not supported on ${stdenv.hostPlatform.system}";
-
-in stdenv.mkDerivation {
-  pname = "slack";
-  inherit version;
-
-  inherit src;
-
     buildInputs = [
       gtk3  # needed for GSETTINGS_SCHEMAS_PATH
     ];
@@ -116,12 +128,26 @@ in stdenv.mkDerivation {
       EOF
       asar pack $out/lib/slack/resources/app.asar.unpacked $out/lib/slack/resources/app.asar
     '';
-
-  meta = with stdenv.lib; {
-    description = "Desktop client for Slack";
-    homepage = https://slack.com;
-    license = licenses.unfree;
-    maintainers = [ maintainers.mmahut ];
-    platforms = [ "x86_64-linux" ];
   };
-}
+
+  darwin = stdenv.mkDerivation {
+    inherit pname version meta;
+
+    phases = [ "installPhase" ];
+
+    src = fetchurl {
+      url = "https://downloads.slack-edge.com/mac_releases/Slack-${version}-macOS.dmg";
+      inherit sha256;
+    };
+
+    installPhase = ''
+      /usr/bin/hdiutil mount -nobrowse -mountpoint slack-mnt $src
+      mkdir -p $out/Applications
+      cp -r ./slack-mnt/Slack.app $out/Applications
+      /usr/bin/hdiutil unmount slack-mnt
+      defaults write com.tinyspeck.slackmacgap SlackNoAutoUpdates -bool YES
+    '';
+  };
+in if stdenv.isDarwin
+  then darwin
+  else linux