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?`.

lib/active_model_serializers/adapter/json_api/pagination_links.rb

@@ -2,6 +2,7 @@ module ActiveModelSerializers
   module Adapter
     class JsonApi < Base
       class PaginationLinks
+        MissingSerializationContextError = Class.new(KeyError)
         FIRST_PAGE = 1
 
         attr_reader :collection, :context
@@ -9,7 +10,13 @@ module ActiveModelSerializers
         def initialize(collection, adapter_options)
           @collection = collection
           @adapter_options = adapter_options
-          @context = adapter_options.fetch(:serialization_context)
+          @context = adapter_options.fetch(:serialization_context) do
+            fail MissingSerializationContextError, <<-EOF.freeze
+ JsonApi::PaginationLinks requires a ActiveModelSerializers::SerializationContext.
+ Please pass a ':serialization_context' option or
+ override CollectionSerializer#paginated? to return 'false'.
+             EOF
+          end
         end
 
         def as_json

lib/active_model_serializers/serialization_context.rb

@@ -1,3 +1,4 @@
+require 'active_support/core_ext/array/extract_options'
 module ActiveModelSerializers
   class SerializationContext
     class << self
@@ -22,9 +23,15 @@ module ActiveModelSerializers
 
     attr_reader :request_url, :query_parameters, :key_transform
 
-    def initialize(request, options = {})
-      @request_url = request.original_url[/\A[^?]+/]
-      @query_parameters = request.query_parameters
+    def initialize(*args)
+      options = args.extract_options!
+      if args.size == 1
+        request = args.pop
+        options[:request_url] = request.original_url[/\A[^?]+/]
+        options[:query_parameters] = request.query_parameters
+      end
+      @request_url = options.delete(:request_url)
+      @query_parameters = options.delete(:query_parameters)
       @url_helpers = options.delete(:url_helpers) || self.class.url_helpers
       @default_url_options = options.delete(:default_url_options) || self.class.default_url_options
     end

lib/grape/helpers/active_model_serializers.rb

@@ -1,4 +1,7 @@
 # Helpers can be included in your Grape endpoint as: helpers Grape::Helpers::ActiveModelSerializers
+
+require 'active_model_serializers/serialization_context'
+
 module Grape
   module Helpers
     module ActiveModelSerializers
@@ -8,6 +11,12 @@ module Grape
       #
       # Example: To include pagination meta data: render(posts, meta: { page: posts.page, total_pages: posts.total_pages })
       def render(resource, active_model_serializer_options = {})
+        active_model_serializer_options.fetch(:serialization_context) do
+          active_model_serializer_options[:serialization_context] = ::ActiveModelSerializers::SerializationContext.new(
+            original_url: request.url[/\A[^?]+/],
+            query_parameters: request.params
+          )
+        end
         env[:active_model_serializer_options] = active_model_serializer_options
         resource
       end