From 26dcd7542354989c09817b4744bdcc5e2e02f5b8 Mon Sep 17 00:00:00 2001
From: Donal McBreen <donal@basecamp.com>
Date: Mon, 11 Sep 2023 15:16:28 +0100
Subject: [PATCH] Add a require_destination setting

If you always want to use a destination, and have a base deploy.yml file
that doesn't specify any hosts, then if you forget to specific the
destination you will get a cryptic error.

Add a "require_destination" setting you can use to avoid this.
---
 lib/kamal/configuration.rb                      | 17 ++++++++++++++---
 test/configuration_test.rb                      | 12 ++++++++++++
 .../fixtures/deploy_for_required_dest.world.yml |  5 +++++
 test/fixtures/deploy_for_required_dest.yml      |  7 +++++++
 4 files changed, 38 insertions(+), 3 deletions(-)
 create mode 100644 test/fixtures/deploy_for_required_dest.world.yml
 create mode 100644 test/fixtures/deploy_for_required_dest.yml

diff --git a/lib/kamal/configuration.rb b/lib/kamal/configuration.rb
index af6e46c5..a77b10ef 100644
--- a/lib/kamal/configuration.rb
+++ b/lib/kamal/configuration.rb
@@ -9,8 +9,7 @@ class Kamal::Configuration
   delegate :service, :image, :servers, :env, :labels, :registry, :stop_wait_time, :hooks_path, to: :raw_config, allow_nil: true
   delegate :argumentize, :optionize, to: Kamal::Utils
 
-  attr_accessor :destination
-  attr_accessor :raw_config
+  attr_reader :destination, :raw_config
 
   class << self
     def create_from(config_file:, destination: nil, version: nil)
@@ -120,6 +119,10 @@ class Kamal::Configuration
     "#{service}-#{version}"
   end
 
+  def require_destination?
+    raw_config.require_destination
+  end
+
 
   def volume_args
     if raw_config.volumes.present?
@@ -161,7 +164,7 @@ class Kamal::Configuration
   end
 
   def valid?
-    ensure_required_keys_present && ensure_valid_kamal_version
+    ensure_destination_if_required && ensure_required_keys_present && ensure_valid_kamal_version
   end
 
 
@@ -243,6 +246,14 @@ class Kamal::Configuration
       true
     end
 
+    def ensure_destination_if_required
+      if require_destination? && destination.nil?
+        raise ArgumentError, "You must specify a destination"
+      end
+
+      true
+    end
+
 
     def role_names
       raw_config.servers.is_a?(Array) ? [ "web" ] : raw_config.servers.keys.sort
diff --git a/test/configuration_test.rb b/test/configuration_test.rb
index f21fdc8d..ca8e7f85 100644
--- a/test/configuration_test.rb
+++ b/test/configuration_test.rb
@@ -210,6 +210,18 @@ class ConfigurationTest < ActiveSupport::TestCase
     end
   end
 
+  test "destination required" do
+    dest_config_file = Pathname.new(File.expand_path("fixtures/deploy_for_required_dest.yml", __dir__))
+
+    assert_raises(ArgumentError) do
+      config = Kamal::Configuration.create_from config_file: dest_config_file
+    end
+
+    assert_nothing_raised do
+      config = Kamal::Configuration.create_from config_file: dest_config_file, destination: "world"
+    end
+  end
+
   test "to_h" do
     expected_config = \
       { :roles=>["web"],
diff --git a/test/fixtures/deploy_for_required_dest.world.yml b/test/fixtures/deploy_for_required_dest.world.yml
new file mode 100644
index 00000000..764dd236
--- /dev/null
+++ b/test/fixtures/deploy_for_required_dest.world.yml
@@ -0,0 +1,5 @@
+servers:
+  - 1.1.1.1
+  - 1.1.1.2
+env:
+  REDIS_URL: redis://x/y
diff --git a/test/fixtures/deploy_for_required_dest.yml b/test/fixtures/deploy_for_required_dest.yml
new file mode 100644
index 00000000..28438363
--- /dev/null
+++ b/test/fixtures/deploy_for_required_dest.yml
@@ -0,0 +1,7 @@
+service: app
+image: dhh/app
+registry:
+  server: registry.digitalocean.com
+  username: <%= "my-user" %>
+  password: <%= "my-password" %>
+require_destination: true