Add bundler-cache feature in dev container.

Addresses the issue of caching bundler dependencies in a Dev Container setup, which can significantly speed up container startup times by avoiding the need to reinstall gems on every new container creation.

Author: viktorianer

railties/lib/rails/generators/rails/devcontainer/templates/devcontainer/compose.yaml.tt

@@ -8,6 +8,7 @@ services:
 
     volumes:
     - ../../<%= app_folder %>:/workspaces/<%= app_folder %>:cached
+    - bundle-cache:/home/vscode/.local/share
 
     # Overrides default command so things don't shut down after the process ends.
     command: sleep infinity
@@ -39,8 +40,10 @@ services:
 
 <%- end -%>
   <%= devcontainer_db_service_yaml(indentation: 4) %>
-<%- if !volumes.empty? -%>
+
 volumes:
+  bundle-cache:
+<%- if !volumes.empty? -%>
 <%- volumes.each do |volume| -%>
   <%= volume %>:
 <%- end -%>

railties/test/generators/app_generator_test.rb

@@ -1576,7 +1576,7 @@ def test_devcontainer
           "context" => "..",
           "dockerfile" => ".devcontainer/Dockerfile"
         },
-        "volumes" => ["../../tmp:/workspaces/tmp:cached"],
+        "volumes" => ["../../tmp:/workspaces/tmp:cached", "bundle-cache:/home/vscode/.local/share"],
         "command" => "sleep infinity",
         "depends_on" => ["selenium"]
       }
@@ -1629,7 +1629,7 @@ def test_devcontainer_no_redis_skipping_solid_action_cable_and_active_job
     assert_compose_file do |compose_config|
       assert_not_includes compose_config["services"]["rails-app"]["depends_on"], "redis"
       assert_nil compose_config["services"]["redis"]
-      assert_nil compose_config["volumes"]
+      assert_includes compose_config["volumes"].keys, "bundle-cache"
     end
 
     assert_devcontainer_json_file do |content|

railties/test/generators/devcontainer_generator_test.rb

@@ -75,6 +75,19 @@ def test_app_folder_option
         end
       end
 
+      def test_app_volumes
+        run_generator
+
+        assert_compose_file do |compose|
+          expected_volumes = ["../../rails_app:/workspaces/rails_app:cached", "bundle-cache:/home/vscode/.local/share"]
+          actual_volumes = compose["services"]["rails-app"]["volumes"]
+          expected_volumes.each do |volume|
+            assert_includes actual_volumes, volume
+          end
+          assert_equal ["bundle-cache", "redis-data"], compose["volumes"].keys
+        end
+      end
+
       def test_database_default_sqlite3
         run_generator
 
@@ -100,7 +113,7 @@ def test_database_mariadb_mysql
             },
           }
           assert_equal expected_mariadb_config, compose["services"]["mariadb"]
-          assert_includes compose["volumes"].keys, "mariadb-data"
+          assert_equal ["bundle-cache", "redis-data", "mariadb-data"], compose["volumes"].keys
           assert_includes compose["services"]["rails-app"]["depends_on"], "mariadb"
         end
 
@@ -127,7 +140,7 @@ def test_database_mariadb_trilogy
             },
           }
           assert_equal expected_mariadb_config, compose["services"]["mariadb"]
-          assert_includes compose["volumes"].keys, "mariadb-data"
+          assert_equal ["bundle-cache", "redis-data", "mariadb-data"], compose["volumes"].keys
           assert_includes compose["services"]["rails-app"]["depends_on"], "mariadb"
         end
 
@@ -154,7 +167,7 @@ def test_database_mysql
             "networks" => ["default"],
           }
           assert_equal expected_mysql_config, compose["services"]["mysql"]
-          assert_includes compose["volumes"].keys, "mysql-data"
+          assert_equal ["bundle-cache", "redis-data", "mysql-data"], compose["volumes"].keys
           assert_includes compose["services"]["rails-app"]["depends_on"], "mysql"
         end
 
@@ -188,7 +201,7 @@ def test_database_postgresql
             }
           }
           assert_equal expected_postgres_config, compose["services"]["postgres"]
-          assert_includes compose["volumes"].keys, "postgres-data"
+          assert_equal ["bundle-cache", "redis-data", "postgres-data"], compose["volumes"].keys
           assert_includes compose["services"]["rails-app"]["depends_on"], "postgres"
         end
 
@@ -216,7 +229,7 @@ def test_database_trilogy
             "networks" => ["default"],
           }
           assert_equal expected_mysql_config, compose["services"]["mysql"]
-          assert_includes compose["volumes"].keys, "mysql-data"
+          assert_equal ["bundle-cache", "redis-data", "mysql-data"], compose["volumes"].keys
           assert_includes compose["services"]["rails-app"]["depends_on"], "mysql"
         end
 
@@ -275,7 +288,7 @@ def test_redis_option_default
             "volumes" => ["redis-data:/data"]
           }
           assert_equal expected_redis_config, compose["services"]["redis"]
-          assert_equal ["redis-data"], compose["volumes"].keys
+          assert_equal ["bundle-cache", "redis-data"], compose["volumes"].keys
         end
 
         assert_devcontainer_json_file do |devcontainer_json|
@@ -291,7 +304,7 @@ def test_redis_option_skip
         assert_compose_file do |compose|
           assert_not_includes compose["services"]["rails-app"]["depends_on"], "redis"
           assert_nil compose["services"]["redis"]
-          assert_nil compose["volumes"]
+          assert_equal ["bundle-cache"], compose["volumes"].keys
         end
 
         assert_devcontainer_json_file do |devcontainer_json|
@@ -380,7 +393,7 @@ def test_common_config_with_folder(folder_name)
                 "context" => "..",
                 "dockerfile" => ".devcontainer/Dockerfile"
               },
-              "volumes" => ["../../#{folder_name}:/workspaces/#{folder_name}:cached"],
+              "volumes" => ["../../#{folder_name}:/workspaces/#{folder_name}:cached", "bundle-cache:/home/vscode/.local/share"],
               "command" => "sleep infinity"
             }
             actual_independent_config = compose["services"]["rails-app"].except("depends_on")