Call super in API.inherited

`API.make_inheritable` was overriding `.inherited` hook on given
instance itself. But it was not calling `super` which is required to
bubble up inheritance chain.

This commit removes `.make_inheritable` and calls `super` instead.

Fixes PR with reproducible spec #2179.

Author: yogeshjain999

CHANGELOG.md

@@ -8,6 +8,7 @@
 
 * [#2176](https://github.com/ruby-grape/grape/pull/2176): Fix: OPTIONS fails if matching all routes - [@myxoh](https://github.com/myxoh).
 * [#2177](https://github.com/ruby-grape/grape/pull/2177): Fix: `default` validator fails if preceded by `as` validator - [@Catsuko](https://github.com/Catsuko).
+* [#2180](https://github.com/ruby-grape/grape/pull/2180): Call `super` in `API.inherited` - [@yogeshjain999](https://github.com/yogeshjain999).
 * Your contribution here.
 ### 1.5.3 (2021/03/07)
 

lib/grape/api.rb

@@ -20,10 +20,11 @@ def new(*args, &block)
 
       # 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
-      def inherited(api, base_instance_parent = Grape::API::Instance)
-        api.initial_setup(base_instance_parent)
+      def inherited(api)
+        super
+
+        api.initial_setup(Grape::API == self ? Grape::API::Instance : @base_instance)
         api.override_all_methods!
-        make_inheritable(api)
       end
 
       # Initialize the instance variables on the remountable class, and the base_instance
@@ -68,15 +69,6 @@ def call(*args, &block)
         instance_for_rack.call(*args, &block)
       end
 
-      # Allows an API to itself be inheritable:
-      def make_inheritable(api)
-        # When a child API inherits from a parent API.
-        def api.inherited(child_api)
-          # The instances of the child API inherit from the instances of the parent API
-          Grape::API.inherited(child_api, base_instance)
-        end
-      end
-
       # Alleviates problems with autoloading by tring to search for the constant
       def const_missing(*args)
         if base_instance.const_defined?(*args)

spec/grape/api_spec.rb

@@ -4081,6 +4081,49 @@ def before
     end
   end
 
+  describe '.inherited' do
+    context 'overriding within class' do
+      let(:root_api) do
+        Class.new(Grape::API) do
+          @bar = 'Hello, world'
+
+          def self.inherited(child_api)
+            super
+            child_api.instance_variable_set(:@foo, @bar.dup)
+          end
+        end
+      end
+
+      let(:child_api) { Class.new(root_api) }
+
+      it 'allows overriding the hook' do
+        expect(child_api.instance_variable_get(:@foo)).to eq('Hello, world')
+      end
+    end
+
+    context 'overriding via composition' do
+      module Inherited
+        def inherited(api)
+          super
+          api.instance_variable_set(:@foo, @bar.dup)
+        end
+      end
+
+      let(:root_api) do
+        Class.new(Grape::API) do
+          @bar = 'Hello, world'
+          extend Inherited
+        end
+      end
+
+      let(:child_api) { Class.new(root_api) }
+
+      it 'allows overriding the hook' do
+        expect(child_api.instance_variable_get(:@foo)).to eq('Hello, world')
+      end
+    end
+  end
+
   describe 'const_missing' do
     subject(:grape_api) { Class.new(Grape::API) }
     let(:mounted) do