Addresses memory issues related to new multi-instance approach (#1836)

Author: myxoh

CHANGELOG.md

@@ -9,6 +9,7 @@
 #### Fixes
 
 * Your contribution here.
+* [#1836](https://github.com/ruby-grape/grape/pull/1836): Fix: memory leak not releasing `call` method calls from setup - [@myxoh](https://github.com/myxoh).
 * [#1830](https://github.com/ruby-grape/grape/pull/1830), [#1829](https://github.com/ruby-grape/grape/issues/1829): Restores `self` sanity - [@myxoh](https://github.com/myxoh).
 
 ### 1.2.1 (2018/11/28)

lib/grape/api.rb

@@ -6,7 +6,7 @@ module Grape
   # should subclass this class in order to build an API.
   class API
     # Class methods that we want to call on the API rather than on the API object
-    NON_OVERRIDABLE = Class.new.methods.freeze
+    NON_OVERRIDABLE = Class.new.methods.freeze + %i[call call!]
 
     class << self
       attr_accessor :base_instance, :instances
@@ -42,6 +42,15 @@ def override_all_methods!
         end
       end
 
+      # 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.
+      # NOTE: This will only be called on an API directly mounted on RACK
+      def call(*args, &block)
+        base_instance.call(*args, &block)
+      end
+
       # Allows an API to itself be inheritable:
       def make_inheritable(api)
         # When a child API inherits from a parent API.

spec/grape/api_spec.rb

@@ -220,6 +220,15 @@ def app
     end
   end
 
+  describe '.call' do
+    context 'it does not add to the app setup' do
+      it 'calls the app' do
+        expect(subject).not_to receive(:add_setup)
+        subject.call({})
+      end
+    end
+  end
+
   describe '.route_param' do
     it 'adds a parameterized route segment namespace' do
       subject.namespace :users do