Avoid multiple mount pollution

CHANGELOG.md

@@ -21,6 +21,7 @@
 * [#2605](https://github.com/ruby-grape/grape/pull/2605): Add Rack 3.2 support with new gemfile and CI integration - [@ericproulx](https://github.com/ericproulx).
 * [#2607](https://github.com/ruby-grape/grape/pull/2607): Remove namespace_stackable and namespace_inheritable from public API - [@ericproulx](https://github.com/ericproulx).
 * Your contribution here.
+* [#2612](https://github.com/ruby-grape/grape/pull/2612): Avoid multiple mount pollution - [@alexanderadam](https://github.com/alexanderadam).
 
 #### Fixes
 

lib/grape/api.rb

@@ -22,14 +22,13 @@ class << self
       attr_accessor :base_instance, :instances
 
       delegate_missing_to :base_instance
-      def_delegators :base_instance, :new, :configuration
 
       # This is the interface point between Rack and Grape; it accepts a request
       # from Rack and ultimately returns an array of three values: the status,
       # the headers, and the body. See [the rack specification]
-      # (http://www.rubydoc.info/github/rack/rack/master/file/SPEC) for more.
+      # (https://github.com/rack/rack/blob/main/SPEC.rdoc) for more.
       # NOTE: This will only be called on an API directly mounted on RACK
-      def_delegators :instance_for_rack, :call, :compile!
+      def_delegators :base_instance, :new, :configuration, :call, :compile!
 
       # When inherited, will create a list of all instances (times the API was mounted)
       # It will listen to the setup required to mount that endpoint, and replicate it on any new instance
@@ -95,14 +94,6 @@ def replay_setup_on(instance)
         end
       end
 
-      def instance_for_rack
-        if never_mounted?
-          base_instance
-        else
-          mounted_instances.first
-        end
-      end
-
       # Adds a new stage to the set up require to get a Grape::API up and running
       def add_setup(step)
         @setup << step

spec/grape/api_spec.rb

@@ -1055,28 +1055,6 @@ def to_txt
     end
   end
 
-  # NOTE: this method is required to preserve the ability of pre-mounting
-  # the root API into a namespace, it may be deprecated in the future.
-  describe 'instance_for_rack' do
-    context 'when the app was not mounted' do
-      it 'returns the base_instance' do
-        expect(app.__send__(:instance_for_rack)).to eq app.base_instance
-      end
-    end
-
-    context 'when the app was mounted' do
-      it 'returns the first mounted instance' do
-        mounted_app = app
-        Class.new(described_class) do
-          namespace 'new_namespace' do
-            mount mounted_app
-          end
-        end
-        expect(app.__send__(:instance_for_rack)).to eq app.__send__(:mounted_instances).first
-      end
-    end
-  end
-
   describe 'filters' do
     it 'adds a before filter' do
       subject.before { @foo = 'first'  }

spec/grape/integration/rack_spec.rb

@@ -71,4 +71,48 @@
       expect(last_response).to be_successful
     end
   end
+
+  # https://github.com/ruby-grape/grape/issues/2576
+  describe 'when an api is mounted' do
+    let(:api) do
+      Class.new(Grape::API) do
+        format :json
+        version 'v1', using: :path
+
+        resource :system do
+          get :ping do
+            { message: 'pong' }
+          end
+        end
+      end
+    end
+
+    let(:parent_api) do
+      api_to_mount = api
+      Class.new(Grape::API) do
+        format :json
+        namespace '/api' do
+          mount api_to_mount
+        end
+      end
+    end
+
+    it 'is not polluted with the parent namespace' do
+      env = Rack::MockRequest.env_for('/v1/api/system/ping', method: 'GET')
+      response = Rack::MockResponse[*parent_api.call(env)]
+
+      expect(response.status).to eq(200)
+      parsed_body = JSON.parse(response.body)
+      expect(parsed_body['message']).to eq('pong')
+    end
+
+    it 'can call the api' do
+      env = Rack::MockRequest.env_for('/v1/system/ping', method: 'GET')
+      response = Rack::MockResponse[*api.call(env)]
+
+      expect(response.status).to eq(200)
+      parsed_body = JSON.parse(response.body)
+      expect(parsed_body['message']).to eq('pong')
+    end
+  end
 end