Check for docker locally before registry login

We were checking before `kamal build push`, but not `kamal registry login`.
Since `kamal registry login` is called first by a deploy we don't
get the nice error message.

lib/kamal/cli.rb

@@ -2,6 +2,7 @@ module Kamal::Cli
   class BootError < StandardError; end
   class HookError < StandardError; end
   class LockError < StandardError; end
+  class DependencyError < StandardError; end
 end
 
 # SSHKit uses instance eval, so we need a global const for ergonomics

lib/kamal/cli/base.rb

@@ -195,5 +195,19 @@ module Kamal::Cli
         ENV.clear
         ENV.update(current_env)
       end
+
+      def ensure_docker_installed
+        run_locally do
+          begin
+            execute *KAMAL.builder.ensure_docker_installed
+          rescue SSHKit::Command::Failed => e
+            error = e.message =~ /command not found/ ?
+              "Docker is not installed locally" :
+              "Docker buildx plugin is not installed locally"
+
+            raise DependencyError, error
+          end
+        end
+      end
   end
 end

lib/kamal/cli/build.rb

@@ -13,7 +13,7 @@ class Kamal::Cli::Build < Kamal::Cli::Base
   def push
     cli = self
 
-    verify_local_dependencies
+    ensure_docker_installed
     run_hook "pre-build"
 
     uncommitted_changes = Kamal::Git.uncommitted_changes
@@ -109,20 +109,6 @@ class Kamal::Cli::Build < Kamal::Cli::Base
   end
 
   private
-    def verify_local_dependencies
-      run_locally do
-        begin
-          execute *KAMAL.builder.ensure_local_dependencies_installed
-        rescue SSHKit::Command::Failed => e
-          build_error = e.message =~ /command not found/ ?
-            "Docker is not installed locally" :
-            "Docker buildx plugin is not installed locally"
-
-          raise BuildError, build_error
-        end
-      end
-    end
-
     def connect_to_remote_host(remote_host)
       remote_uri = URI.parse(remote_host)
       if remote_uri.scheme == "ssh"

lib/kamal/cli/registry.rb

@@ -3,6 +3,8 @@ class Kamal::Cli::Registry < Kamal::Cli::Base
   option :skip_local, aliases: "-L", type: :boolean, default: false, desc: "Skip local login"
   option :skip_remote, aliases: "-R", type: :boolean, default: false, desc: "Skip remote login"
   def login
+    ensure_docker_installed
+
     run_locally    { execute *KAMAL.registry.login } unless options[:skip_local]
     on(KAMAL.hosts) { execute *KAMAL.registry.login } unless options[:skip_remote]
   end

lib/kamal/commands/base.rb

@@ -34,6 +34,12 @@ module Kamal::Commands
       [ :rm, path ]
     end
 
+    def ensure_docker_installed
+      combine \
+        ensure_local_docker_installed,
+        ensure_local_buildx_installed
+    end
+
     private
       def combine(*commands, by: "&&")
         commands
@@ -104,5 +110,13 @@ module Kamal::Commands
           " -i #{key}"
         end
       end
+
+      def ensure_local_docker_installed
+        docker "--version"
+      end
+
+      def ensure_local_buildx_installed
+        docker :buildx, "version"
+      end
   end
 end

lib/kamal/commands/builder.rb

@@ -33,24 +33,4 @@ class Kamal::Commands::Builder < Kamal::Commands::Base
   def hybrid
     @hybrid ||= Kamal::Commands::Builder::Hybrid.new(config)
   end
-
-
-  def ensure_local_dependencies_installed
-    if name.native?
-      ensure_local_docker_installed
-    else
-      combine \
-        ensure_local_docker_installed,
-        ensure_local_buildx_installed
-    end
-  end
-
-  private
-    def ensure_local_docker_installed
-      docker "--version"
-    end
-
-    def ensure_local_buildx_installed
-      docker :buildx, "version"
-    end
 end

test/cli/build_test.rb

@@ -155,7 +155,7 @@ class CliBuildTest < CliTestCase
       .raises(SSHKit::Command::Failed.new("no buildx"))
 
     Kamal::Commands::Builder.any_instance.stubs(:native_and_local?).returns(false)
-    assert_raises(Kamal::Cli::Build::BuildError) { run_command("push") }
+    assert_raises(Kamal::Cli::DependencyError) { run_command("push") }
   end
 
   test "push pre-build hook failure" do

test/cli/registry_test.rb

@@ -43,6 +43,16 @@ class CliRegistryTest < CliTestCase
     end
   end
 
+  test "login with no docker" do
+    stub_setup
+    SSHKit::Backend::Abstract.any_instance.stubs(:execute)
+      .with(:docker, "--version", "&&", :docker, :buildx, "version")
+      .raises(SSHKit::Command::Failed.new("command not found"))
+
+    assert_raises(Kamal::Cli::DependencyError) { run_command("login") }
+  end
+
+
   private
     def run_command(*command)
       stdouted { Kamal::Cli::Registry.start([ *command, "-c", "test/fixtures/deploy_with_accessories.yml" ]) }