Add pack option to the builder options for cloud native buildpacks

lib/kamal/commands/base.rb

@@ -77,6 +77,10 @@ def docker(*args)
         args.compact.unshift :docker
       end
 
+      def pack(*args)
+        args.compact.unshift :pack
+      end
+
       def git(*args, path: nil)
         [ :git, *([ "-C", path ] if path), *args.compact ]
       end

lib/kamal/commands/builder.rb

@@ -2,7 +2,7 @@
 
 class Kamal::Commands::Builder < Kamal::Commands::Base
   delegate :create, :remove, :push, :clean, :pull, :info, :inspect_builder, :validate_image, :first_mirror, to: :target
-  delegate :local?, :remote?, to: "config.builder"
+  delegate :local?, :remote?, :pack?, to: "config.builder"
 
   include Clone
 
@@ -17,6 +17,8 @@ def target
       else
         remote
       end
+    elsif pack?
+      pack
     else
       local
     end
@@ -34,6 +36,9 @@ def hybrid
     @hybrid ||= Kamal::Commands::Builder::Hybrid.new(config)
   end
 
+  def pack
+    @pack ||= Kamal::Commands::Builder::Pack.new(config)
+  end
 
   def ensure_local_dependencies_installed
     if name.native?

lib/kamal/commands/builder/base.rb

@@ -6,6 +6,7 @@ class BuilderError < StandardError; end
   delegate :argumentize, to: Kamal::Utils
   delegate \
     :args, :secrets, :dockerfile, :target, :arches, :local_arches, :remote_arches, :remote,
+    :pack?, :pack_builder, :pack_buildpacks,
     :cache_from, :cache_to, :ssh, :driver, :docker_driver?,
     to: :builder_config
 
@@ -33,7 +34,7 @@ def info
   end
 
   def inspect_builder
-    docker :buildx, :inspect, builder_name unless docker_driver?
+    docker :buildx, :inspect, builder_name unless docker_driver? || pack?
   end
 
   def build_options

lib/kamal/commands/builder/pack.rb

@@ -0,0 +1,26 @@
+class Kamal::Commands::Builder::Pack < Kamal::Commands::Builder::Base
+  def push
+    combine \
+      pack(:build,
+        config.repository,
+        "--platform", platform,
+        "--builder", pack_builder,
+        buildpacks,
+        "-t", config.absolute_image,
+        "-t", config.latest_image,
+        "--env", "BP_IMAGE_LABELS=service=#{config.service}",
+        secrets.map { |secret| [ "--env", Kamal::Utils.sensitive(ENV[secret]) ] },
+        "--path", build_context),
+      docker(:push, config.absolute_image),
+      docker(:push, config.latest_image)
+  end
+
+  private
+    def platform
+      "linux/#{local_arches.first}"
+    end
+
+    def buildpacks
+      (pack_buildpacks << "paketo-buildpacks/image-labels").map { |buildpack| [ "--buildpack", buildpack ] }
+    end
+end

lib/kamal/configuration/builder.rb

@@ -57,6 +57,10 @@ def cached?
     !!builder_config["cache"]
   end
 
+  def pack?
+    !!builder_config["pack"]
+  end
+
   def args
     builder_config["args"] || {}
   end
@@ -81,6 +85,14 @@ def driver
     builder_config.fetch("driver", "docker-container")
   end
 
+  def pack_builder
+    builder_config["pack"]["builder"] if pack?
+  end
+
+  def pack_buildpacks
+    builder_config["pack"]["buildpacks"] if pack?
+  end
+
   def local_disabled?
     builder_config["local"] == false
   end

lib/kamal/configuration/docs/builder.yml

@@ -35,6 +35,15 @@ builder:
   # Defaults to true
   local: true
 
+  # Buildpack configuration
+  #
+  # The build configuration for using pack to build a Cloud Native Buildpack image.
+  pack:
+    builder: heroku/builder:24
+    buildpacks:
+    - heroku/ruby
+    - heroku/procfile
+
   # Builder cache
   #
   # The type must be either 'gha' or 'registry'

test/commands/builder_test.rb

@@ -61,6 +61,14 @@ class CommandsBuilderTest < ActiveSupport::TestCase
       builder.push.join(" ")
   end
 
+  test "target pack when pack is set" do
+    builder = new_builder_command(image: "dhh/app", builder: { "arch" => "amd64", "pack" => { "builder" => "heroku/builder:24", "buildpacks" => [ "heroku/ruby", "heroku/procfile" ] } })
+    assert_equal "pack", builder.name
+    assert_equal \
+      "pack build dhh/app --platform linux/amd64 --builder heroku/builder:24 --buildpack heroku/ruby --buildpack heroku/procfile --buildpack paketo-buildpacks/image-labels -t dhh/app:123 -t dhh/app:latest --env BP_IMAGE_LABELS=service=app --path . && docker push dhh/app:123 && docker push dhh/app:latest",
+      builder.push.join(" ")
+  end
+
   test "build args" do
     builder = new_builder_command(builder: { "args" => { "a" => 1, "b" => 2 } })
     assert_equal \

test/configuration/builder_test.rb

@@ -16,6 +16,23 @@ class ConfigurationBuilderTest < ActiveSupport::TestCase
     assert_equal false, config.builder.remote?
   end
 
+  test "pack?" do
+    assert_not config.builder.pack?
+  end
+
+  test "pack? with pack builder" do
+    @deploy[:builder] = { "arch" => "arm64", "pack" => { "builder" => "heroku/builder:24" } }
+
+    assert config.builder.pack?
+  end
+
+  test "pack details" do
+    @deploy[:builder] = { "arch" => "amd64", "pack" => { "builder" => "heroku/builder:24", "buildpacks" => [ "heroku/ruby", "heroku/procfile" ] } }
+
+    assert_equal "heroku/builder:24", config.builder.pack_builder
+    assert_equal [ "heroku/ruby", "heroku/procfile" ], config.builder.pack_buildpacks
+  end
+
   test "remote" do
     assert_nil config.builder.remote
   end