Check destination before eager loading sub-configs

lib/kamal/configuration.rb

@@ -58,6 +58,8 @@ def initialize(raw_config, destination: nil, version: nil, validate: true)
 
     validate! raw_config, example: validation_yml.symbolize_keys, context: "", with: Kamal::Configuration::Validator::Configuration
 
+    ensure_destination_if_required
+
     @secrets = Kamal::Secrets.new(destination: destination, secrets_path: secrets_path)
 
     # Eager load config to validate it, these are first as they have dependencies later on
@@ -77,7 +79,6 @@ def initialize(raw_config, destination: nil, version: nil, validate: true)
     @ssh = Ssh.new(config: self)
     @sshkit = Sshkit.new(config: self)
 
-    ensure_destination_if_required
     ensure_required_keys_present
     ensure_valid_kamal_version
     ensure_retain_containers_valid

test/configuration_test.rb

@@ -287,6 +287,20 @@ class ConfigurationTest < ActiveSupport::TestCase
     end
   end
 
+  test "destination check precedes sub-config validation" do
+    # A destination-only key (builder.arch) lives only in the destination file, so
+    # the base config is incomplete. The missing-destination guard must run before
+    # the sub-configs validate themselves, otherwise "Builder arch not set" masks
+    # the real cause.
+    @deploy.delete(:builder)
+    @deploy[:require_destination] = true
+
+    error = assert_raises(ArgumentError) do
+      Kamal::Configuration.new(@deploy)
+    end
+    assert_equal "You must specify a destination", error.message
+  end
+
   test "to_h" do
     expected_config = \
       { roles: [ "web" ],