Modules section for dip

README.md

@@ -238,6 +238,92 @@ services:
 
 The container will run using the same user ID as your host machine.
 
+### Modules
+
+Modules are defined as array in `modules` section of dip.yml, modules are stored in `.dip` subdirectory of dip.yml directory.
+
+The main purpose of modules is to improve maintainability for a group of projects.
+Imagine having multiple gems which are managed with dip, each of them has the same commands, so to change one command in dip you need to update all gems individualy.
+
+With `modules` you can define a group of modules for dip.
+
+For example having setup as this:
+
+```yml
+# ./dip.yml
+modules:
+ - sasts
+ - rails
+
+...
+```
+
+```yml
+# ./.dip/sasts.yml
+interaction:
+  brakeman:
+    description: Check brakeman sast
+    command: docker run ...
+```
+
+```yml
+# ./.dip/rails.yml
+interaction:
+  annotate:
+    description: Run annotate command
+    service: backend
+    command: bundle exec annotate
+```
+
+Will be expanded to:
+
+```yml
+# resultant configuration
+interaction:
+  brakeman:
+    description: Check brakeman sast
+    command: docker run ...
+  annotate:
+    description: Run annotate command
+    service: backend
+    command: bundle exec annotate
+```
+
+Imagine `.dip` to be a submodule so it can be managed only in one place.
+
+If you want to override module command, you can redefine it in dip.yml
+
+```yml
+# ./dip.yml
+modules:
+ - sasts
+
+interaction:
+  brakeman:
+    description: Check brakeman sast
+    command: docker run another-image ...
+```
+
+```yml
+# ./.dip/sasts.yml
+interaction:
+  brakeman:
+    description: Check brakeman sast
+    command: docker run some-image ...
+```
+
+Will be expanded to:
+
+```yml
+# resultant configuration
+interaction:
+  brakeman:
+    description: Check brakeman sast
+    command: docker run another-image ...
+```
+
+Nested modules are not supported.
+
 ### dip run
 
 Run commands defined within the `interaction` section of dip.yml

lib/dip/config.rb

@@ -43,6 +43,10 @@ def exist?
         file_path&.exist?
       end
 
+      def modules_dir
+        file_path.dirname / ".dip"
+      end
+
       private
 
       attr_reader :override
@@ -90,6 +94,10 @@ def file_path
       finder.file_path
     end
 
+    def module_file(filename)
+      finder.modules_dir / "#{filename}.yml"
+    end
+
     def exist?
       finder.exist?
     end
@@ -125,10 +133,28 @@ def config
                                     "Please upgrade your dip!"
       end
 
+      base_config = {}
+
+      if (modules = config[:modules])
+        raise Dip::Error, "Modules should be specified as array" unless modules.is_a?(Array)
+
+        modules.each do |m|
+          file = module_file(m)
+          raise Dip::Error, "Could not find module `#{m}`" unless file.exist?
+
+          module_config = self.class.load_yaml(file)
+          raise Dip::Error, "Nested modules are not supported" if module_config[:modules]
+
+          base_config.deep_merge!(module_config)
+        end
+      end
+
+      base_config.deep_merge!(config)
+
       override_finder = ConfigFinder.new(work_dir, override: true)
-      config.deep_merge!(self.class.load_yaml(override_finder.file_path)) if override_finder.exist?
+      base_config.deep_merge!(self.class.load_yaml(override_finder.file_path)) if override_finder.exist?
 
-      @config = CONFIG_DEFAULTS.merge(config)
+      @config = CONFIG_DEFAULTS.merge(base_config)
     end
 
     def config_missing_error(config_key)

spec/fixtures/modules/.dip/first.yml

@@ -0,0 +1,3 @@
+interaction:
+  test_app:
+    service: test_backend

spec/fixtures/modules/.dip/last.yml

@@ -0,0 +1,3 @@
+interaction:
+  test_app:
+    service: test_frontend

spec/fixtures/modules/.dip/test.yml

@@ -0,0 +1,3 @@
+interaction:
+  app:
+    service: backend

spec/fixtures/modules/dip.yml

@@ -0,0 +1,17 @@
+version: '2'
+
+modules:
+  - first
+  - last
+  - test
+
+environment:
+  FOO: bar
+
+compose:
+  files:
+    - docker-compose.yml
+
+interaction:
+  app1:
+    service: frontend

spec/fixtures/unknown_module/dip.yml

@@ -0,0 +1,4 @@
+version: '2'
+
+modules:
+  - unknown

spec/lib/dip/config_spec.rb

@@ -53,6 +53,30 @@
     end
   end
 
+  context "when config has modules", :env do
+    let(:env) { {"DIP_FILE" => fixture_path("modules", "dip.yml")} }
+
+    it "expands modules to main config" do
+      expect(subject.interaction[:app][:service]).to eq "backend"
+    end
+
+    it "merges modules to main config" do
+      expect(subject.interaction[:app1][:service]).to eq "frontend"
+    end
+
+    it "overrides first defined module with the last one" do
+      expect(subject.interaction[:test_app][:service]).to eq "test_frontend"
+    end
+  end
+
+  context "when config has unknown module", :env do
+    let(:env) { {"DIP_FILE" => fixture_path("unknown_module", "dip.yml")} }
+
+    it "raises and error" do
+      expect { subject.interaction }.to raise_error(Dip::Error, /Could not find module/)
+    end
+  end
+
   context "when config located two levels higher and overridden at one level higher", :env do
     subject { described_class.new(fixture_path("cascade", "sub_a", "sub_b")) }