Fix #1759, Grape integration, adds serialization_context

- improves improves serialization_context to take options and not depend
on a `request` object.
- adds descriptive error on missing serialization_context.
- Document overriding `CollectionSerializer#paginated?`.

test/active_model_serializers/serialization_context_test_isolated.rb

@@ -5,13 +5,19 @@ require 'minitest/mock'
 class SerializationContextTest < ActiveSupport::TestCase
   include ActiveSupport::Testing::Isolation
 
-  def create_request
-    request = Minitest::Mock.new
-    request.expect(:original_url, 'original_url')
-    request.expect(:query_parameters, 'query_parameters')
-  end
-
   class WithRails < SerializationContextTest
+    def create_request
+      request = ActionDispatch::Request.new({})
+      def request.original_url
+        'http://example.com/articles?page=2'
+      end
+
+      def request.query_parameters
+        { 'page' => 2 }
+      end
+      request
+    end
+
     setup do
       require 'rails'
       require 'active_model_serializers'
@@ -20,8 +26,8 @@ class SerializationContextTest < ActiveSupport::TestCase
     end
 
     test 'create context with request url and query parameters' do
-      assert_equal @context.request_url, 'original_url'
-      assert_equal @context.query_parameters, 'query_parameters'
+      assert_equal @context.request_url, 'http://example.com/articles'
+      assert_equal @context.query_parameters, 'page' => 2
     end
 
     test 'url_helpers is set up for Rails url_helpers' do
@@ -36,14 +42,21 @@ class SerializationContextTest < ActiveSupport::TestCase
   end
 
   class WithoutRails < SerializationContextTest
+    def create_request
+      {
+        request_url: 'http://example.com/articles',
+        query_parameters: { 'page' => 2 }
+      }
+    end
+
     setup do
       require 'active_model_serializers/serialization_context'
       @context = ActiveModelSerializers::SerializationContext.new(create_request)
     end
 
     test 'create context with request url and query parameters' do
-      assert_equal @context.request_url, 'original_url'
-      assert_equal @context.query_parameters, 'query_parameters'
+      assert_equal @context.request_url, 'http://example.com/articles'
+      assert_equal @context.query_parameters, 'page' => 2
     end
 
     test 'url_helpers is a module when Rails is not present' do

test/adapter/json_api/pagination_links_test.rb

@@ -161,6 +161,17 @@ module ActiveModelSerializers
 
           assert_equal expected_response_without_pagination_links, adapter.serializable_hash
         end
+
+        def test_raises_descriptive_error_when_serialization_context_unset
+          render_options = { adapter: :json_api }
+          adapter = serializable(using_kaminari, render_options)
+          exception = assert_raises do
+            adapter.as_json
+          end
+          exception_class = ActiveModelSerializers::Adapter::JsonApi::PaginationLinks::MissingSerializationContextError
+          assert_equal exception_class, exception.class
+          assert_match(/CollectionSerializer#paginated\?/, exception.message)
+        end
       end
     end
   end