Helper method to access controller context in middleware

CHANGELOG.md

@@ -3,6 +3,7 @@
 #### Features
 
 * Your contribution here.
+* [#1918](https://github.com/ruby-grape/grape/pull/1918): Helper methods to access controller context from middleware - [@NikolayRys](https://github.com/NikolayRys).
 * [#1915](https://github.com/ruby-grape/grape/pull/1915): Micro optimizations in allocating hashes and arrays - [@dnesteryuk](https://github.com/dnesteryuk).
 * [#1904](https://github.com/ruby-grape/grape/pull/1904): Allows Grape to load files on startup rather than on the first call - [@myxoh](https://github.com/myxoh).
 * [#1907](https://github.com/ruby-grape/grape/pull/1907): Adds outside configuration to Grape with `configure` - [@unleashy](https://github.com/unleashy).

README.md

@@ -2497,6 +2497,17 @@ class Twitter::API < Grape::API
 end
 ```
 
+Inside the `rescue_from` block, the environment of the original controller method(`.self` receiver) is accessible through the `#context` method.
+
+```ruby
+class Twitter::API < Grape::API
+  rescue_from :all do |e|
+    user_id = context.params[:user_id]
+    error!("error for #{user_id}")
+  end
+end
+```
+
 #### Rescuing exceptions inside namespaces
 
 You could put `rescue_from` clauses inside a namespace and they will take precedence over ones
@@ -3121,6 +3132,8 @@ end
 
 Use [Doorkeeper](https://github.com/doorkeeper-gem/doorkeeper), [warden-oauth2](https://github.com/opperator/warden-oauth2) or [rack-oauth2](https://github.com/nov/rack-oauth2) for OAuth2 support.
 
+You can access the controller params, headers, and helpers through the context with the `#context` method inside any auth middleware inherited from `Grape::Middlware::Auth::Base`.
+
 ## Describing and Inspecting an API
 
 Grape routes can be reflected at runtime. This can notably be useful for generating documentation.
@@ -3433,6 +3446,8 @@ class API < Grape::API
 end
 ```
 
+You can access the controller params, headers, and helpers through the context with the `#context` method inside any middleware inherited from `Grape::Middlware::Base`.
+
 ### Rails Middleware
 
 Note that when you're using Grape mounted on Rails you don't have to use Rails middleware because it's already included into your middleware stack.

lib/grape.rb

@@ -111,6 +111,7 @@ module Middleware
       autoload :Error
       autoload :Globals
       autoload :Stack
+      autoload :Helpers
     end
 
     module Auth

lib/grape/middleware/auth/base.rb

@@ -4,17 +4,15 @@ module Grape
   module Middleware
     module Auth
       class Base
+        include Helpers
+
         attr_accessor :options, :app, :env
 
         def initialize(app, **options)
           @app = app
           @options = options
         end
 
-        def context
-          env[Grape::Env::API_ENDPOINT]
-        end
-
         def call(env)
           dup._call(env)
         end

lib/grape/middleware/base.rb

@@ -3,6 +3,8 @@
 module Grape
   module Middleware
     class Base
+      include Helpers
+
       attr_reader :app, :env, :options
       TEXT_HTML = 'text/html'.freeze
 

lib/grape/middleware/helpers.rb

@@ -0,0 +1,10 @@
+module Grape
+  module Middleware
+    # Common methods for all types of Grape middleware
+    module Helpers
+      def context
+        env[Grape::Env::API_ENDPOINT]
+      end
+    end
+  end
+end

spec/grape/middleware/base_spec.rb

@@ -114,6 +114,14 @@
     end
   end
 
+  describe '#context' do
+    subject { Grape::Middleware::Base.new(blank_app) }
+    it 'allows access to response context' do
+      subject.call(Grape::Env::API_ENDPOINT => { header: 'some header' })
+      expect(subject.context).to eq(header: 'some header')
+    end
+  end
+
   context 'options' do
     it 'persists options passed at initialization' do
       expect(Grape::Middleware::Base.new(blank_app, abc: true).options[:abc]).to be true