Application 'linking' done right (#1396)

modules/system/applications.nix

@@ -1,18 +1,60 @@
-{ config, lib, pkgs, ... }:
-
-with lib;
-
-let
-
-  cfg = config.system;
-
-in
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
 
 {
-  options = {
-  };
-
   config = {
+    system.checks.text = lib.mkAfter ''
+      ensureAppManagement() {
+        for appBundle in /Applications/Nix\ Apps/*.app; do
+          if [[ -d "$appBundle" ]]; then
+            if ! touch "$appBundle/.DS_Store" &> /dev/null; then
+              return 1
+            fi
+          fi
+        done
+
+        return 0
+      }
+
+      if ! ensureAppManagement; then
+        if [[ "$(launchctl managername)" != Aqua ]]; then
+          # It is possible to grant the App Management permission to `sshd-keygen-wrapper`, however
+          # there are many pitfalls like requiring the primary user to grant the permission and to
+          # be logged in when `darwin-rebuild` is run over SSH and it will still fail sometimes...
+          printf >&2 '\e[1;31merror: permission denied when trying to update apps over SSH, aborting activation\e[0m\n'
+          printf >&2 'Apps could not be updated as `darwin-rebuild` requires Full Disk Access to work over SSH.\n'
+          printf >&2 'You can either:\n'
+          printf >&2 '\n'
+          printf >&2 '  grant Full Disk Access to all programs run over SSH\n'
+          printf >&2 '\n'
+          printf >&2 'or\n'
+          printf >&2 '\n'
+          printf >&2 '  run `darwin-rebuild` in a graphical session.\n'
+          printf >&2 '\n'
+          printf >&2 'The option "Allow full disk access for remote users" can be found by\n'
+          printf >&2 'navigating to System Settings > General > Sharing > Remote Login\n'
+          printf >&2 'and then pressing on the i icon next to the switch.\n'
+          exit 1
+        else
+          # The TCC service required to modify notarised app bundles is `kTCCServiceSystemPolicyAppBundles`
+          # and we can reset it to ensure the user gets another prompt
+          tccutil reset SystemPolicyAppBundles > /dev/null
+
+          if ! ensureAppManagement; then
+            printf >&2 '\e[1;31merror: permission denied when trying to update apps, aborting activation\e[0m\n'
+            printf >&2 '`darwin-rebuild` requires permission to update your apps, please accept the notification\n'
+            printf >&2 'and grant the permission for your terminal emulator in System Settings.\n'
+            printf >&2 '\n'
+            printf >&2 'If you did not get a notification, you can navigate to System Settings > Privacy & Security > App Management.\n'
+            exit 1
+          fi
+        fi
+      fi
+    '';
 
     system.build.applications = pkgs.buildEnv {
       name = "system-applications";
@@ -40,13 +82,33 @@ in
         fi
       ''}
 
-      if [ ! -e '/Applications/Nix Apps' ] \
-         || ourLink '/Applications/Nix Apps'; then
-        ln -sfn ${cfg.build.applications}/Applications '/Applications/Nix Apps'
-      else
-        echo "warning: /Applications/Nix Apps is not owned by nix-darwin, skipping App linking..." >&2
-      fi
-    '';
+      targetFolder='/Applications/Nix Apps'
 
+      # Clean up old style symlink to nix store
+      if [ -e "$targetFolder" ] && ourLink "$targetFolder"; then
+        rm "$targetFolder"
+      fi
+
+      mkdir -p "$targetFolder"
+
+      rsyncFlags=(
+        # mtime is standardized in the nix store, which would leave only file size to distinguish files.
+        # Thus we need checksums, despite the speed penalty.
+        --checksum
+        # Converts all symlinks pointing outside of the copied tree (thus unsafe) into real files and directories.
+        # This neatly converts all the symlinks pointing to application bundles in the nix store into
+        # real directories, without breaking any relative symlinks inside of application bundles.
+        # This is good enough, because the make-symlinks-relative.sh setup hook converts all $out internal
+        # symlinks to relative ones.
+        --copy-unsafe-links
+        --archive
+        --delete
+        --chmod=-w
+        --no-group
+        --no-owner
+      )
+
+      ${lib.getExe pkgs.rsync} "''${rsyncFlags[@]}" ${config.system.build.applications}/Applications/ "$targetFolder"
+    '';
   };
 }