From 79baa598fa99afc80cf0dea8317122b1fea1dcfb Mon Sep 17 00:00:00 2001
From: Matthew Kent <matthew@37signals.com>
Date: Fri, 24 Nov 2023 15:35:36 -0800
Subject: [PATCH 1/2] Make an effort to match the primary_role from a list of
 specific roles.

This is less surprising than picking the first role and first host.
---
 lib/kamal/commander.rb | 3 ++-
 test/commander_test.rb | 9 +++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/lib/kamal/commander.rb b/lib/kamal/commander.rb
index 35939fe7d..ded958eb8 100644
--- a/lib/kamal/commander.rb
+++ b/lib/kamal/commander.rb
@@ -36,7 +36,8 @@ def specific_hosts=(hosts)
   end
 
   def primary_host
-    specific_hosts&.first || specific_roles&.first&.primary_host || config.primary_host
+    # Given a list of specific roles, make an effort to match up with the primary_role
+    specific_hosts&.first || specific_roles&.detect { |role| role.name == config.primary_role }&.primary_host || specific_roles&.first&.primary_host || config.primary_host
   end
 
   def primary_role
diff --git a/test/commander_test.rb b/test/commander_test.rb
index 06cc5bbb1..d98026685 100644
--- a/test/commander_test.rb
+++ b/test/commander_test.rb
@@ -100,6 +100,15 @@ class CommanderTest < ActiveSupport::TestCase
     assert_equal({ in: :groups, limit: 1, wait: 2 }, @kamal.boot_strategy)
   end
 
+  test "try to match the primary role from a list of specific roles" do
+    configure_with(:deploy_primary_web_role_override)
+
+    @kamal.specific_roles = [ "web_*" ]
+    assert_equal [ "web_chicago", "web_tokyo" ], @kamal.roles.map(&:name)
+    assert_equal "web_tokyo", @kamal.primary_role
+    assert_equal "1.1.1.3", @kamal.primary_host
+  end
+
   private
     def configure_with(variant)
       @kamal = Kamal::Commander.new.tap do |kamal|

From 63babecba745460543d129fc94bedebe7f8e40a4 Mon Sep 17 00:00:00 2001
From: Matthew Kent <matthew@37signals.com>
Date: Fri, 24 Nov 2023 21:18:06 -0800
Subject: [PATCH 2/2] Raise an error when either the filtered hosts or roles
 are empty.

Keeps us confusingly running things on the primary_host when nothing
matches.
---
 lib/kamal/commander.rb | 20 ++++++++++++++++++--
 test/commander_test.rb | 17 +++++++++++++----
 2 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/lib/kamal/commander.rb b/lib/kamal/commander.rb
index ded958eb8..0a4f4b927 100644
--- a/lib/kamal/commander.rb
+++ b/lib/kamal/commander.rb
@@ -28,11 +28,27 @@ def specific_primary!
   end
 
   def specific_roles=(role_names)
-    @specific_roles = Kamal::Utils.filter_specific_items(role_names, config.roles) if role_names.present?
+    if role_names.present?
+      @specific_roles = Kamal::Utils.filter_specific_items(role_names, config.roles)
+
+      if @specific_roles.empty?
+        raise ArgumentError, "No --roles match for #{role_names.join(',')}"
+      end
+
+      @specific_roles
+    end
   end
 
   def specific_hosts=(hosts)
-    @specific_hosts = Kamal::Utils.filter_specific_items(hosts, config.all_hosts) if hosts.present?
+    if hosts.present?
+      @specific_hosts = Kamal::Utils.filter_specific_items(hosts, config.all_hosts)
+
+      if @specific_hosts.empty?
+        raise ArgumentError, "No --hosts match for #{hosts.join(',')}"
+      end
+
+      @specific_hosts
+    end
   end
 
   def primary_host
diff --git a/test/commander_test.rb b/test/commander_test.rb
index d98026685..4e848a4b1 100644
--- a/test/commander_test.rb
+++ b/test/commander_test.rb
@@ -24,8 +24,10 @@ class CommanderTest < ActiveSupport::TestCase
     @kamal.specific_hosts = [ "*" ]
     assert_equal [ "1.1.1.1", "1.1.1.2", "1.1.1.3", "1.1.1.4" ], @kamal.hosts
 
-    @kamal.specific_hosts = [ "*miss" ]
-    assert_equal [], @kamal.hosts
+    exception = assert_raises(ArgumentError) do
+      @kamal.specific_hosts = [ "*miss" ]
+    end
+    assert_match /hosts match for \*miss/, exception.message
   end
 
   test "filtering hosts by filtering roles" do
@@ -33,6 +35,11 @@ class CommanderTest < ActiveSupport::TestCase
 
     @kamal.specific_roles = [ "web" ]
     assert_equal [ "1.1.1.1", "1.1.1.2" ], @kamal.hosts
+
+    exception = assert_raises(ArgumentError) do
+      @kamal.specific_roles = [ "*miss" ]
+    end
+    assert_match /roles match for \*miss/, exception.message
   end
 
   test "filtering roles" do
@@ -50,8 +57,10 @@ class CommanderTest < ActiveSupport::TestCase
     @kamal.specific_roles = [ "*" ]
     assert_equal [ "web", "workers" ], @kamal.roles.map(&:name)
 
-    @kamal.specific_roles = [ "*miss" ]
-    assert_equal [], @kamal.roles.map(&:name)
+    exception = assert_raises(ArgumentError) do
+      @kamal.specific_roles = [ "*miss" ]
+    end
+    assert_match /roles match for \*miss/, exception.message
   end
 
   test "filtering roles by filtering hosts" do