Allow caller to provide a custom data-mapper

lib/brainstem/presenter_collection.rb

@@ -33,6 +33,7 @@ def initialize
     # @option options [Boolean] :apply_default_filters Determine if Presenter's filter defaults should be applied.  On by default.
     # @option options [Brainstem::Presenter] :primary_presenter The Presenter to use for filters and sorts. If unspecified, the +:model+ or +name+ will be used to find an appropriate Presenter.
     # @option options [paginator] :paginator Optional custom paginator. If unspecified, the default paginator will be used.
+    # @option options [data_mapper] :paginator Optional custom data mapper. If unspecified, the default data mapper will be used.
     # @yield Must return a scope on the model +name+, which will then be presented.
     # @return [Hash] A hash of arrays of hashes. Top-level hash keys are pluralized model names, with values of arrays containing one hash per object that was found by the given given options.
     def presenting(name, options = {}, &block)

lib/brainstem/query_strategies/base_strategy.rb

@@ -83,7 +83,7 @@ def paginator
       end
 
       def data_mapper
-        Brainstem::QueryStrategies::DataMapper.new
+        @data_mapper ||= @options[:data_mapper] || Brainstem::QueryStrategies::DataMapper.new
       end
     end
   end

lib/brainstem/query_strategies/data_mapper.rb

@@ -2,9 +2,20 @@ module Brainstem
   module QueryStrategies
     class DataMapper
       def get_models(ids:, scope:)
-        id_lookup = {}
-        ids.each.with_index { |id, index| id_lookup[id] = index }
-        scope.klass.where(id: ids).sort_by { |model| id_lookup[model.id] }
+        models = _get_models(scope, ids)
+        sort_models(models, ids)
+      end
+
+      private
+
+      def _get_models(scope, ids)
+        scope.klass.where(id: ids)
+      end
+
+      def sort_models(models, ids)
+        model_order = {}
+        ids.each.with_index { |id, index| model_order[id] = index }
+        models.sort_by { |model| model_order[model.id] }
       end
     end
   end

spec/brainstem/query_strategies/data_mapper_spec.rb

@@ -0,0 +1,14 @@
+require "spec_helper"
+
+describe Brainstem::QueryStrategies::DataMapper do
+  describe "#get_models" do
+    it 'gets all models in the ids list sorted by list order, not the scope' do
+      scope = Workspace.order(:id).limit(10)
+      ids = scope.map(&:id).shuffle
+      expect(ids.length).to be > 3
+
+      models = subject.get_models(ids: ids, scope: scope)
+      expect(models.map(&:id)).to eq ids
+    end
+  end
+end

spec/brainstem/query_strategies/filter_and_search_spec.rb

@@ -63,6 +63,17 @@ def run_query
         end
       end
 
+      context 'when options contain a data_mapper' do
+        let(:data_mapper) { Object.new }
+        let(:options) { default_options.merge(data_mapper: data_mapper) }
+
+        it 'uses the provided data_mapper' do
+          mock(data_mapper).get_models(anything) { [] }
+          query_strategy = described_class.new(options)
+          query_strategy.execute(Workspace.unscoped)
+        end
+      end
+
       context 'with limit and offset params' do
         let(:limit) { 2 }
         let(:offset) { 4 }

spec/brainstem/query_strategies/filter_or_search_spec.rb

@@ -55,6 +55,16 @@
           subject.execute(Workspace.unscoped)
         end
       end
+
+      context 'when options contain a data_mapper' do
+        let(:data_mapper) { Object.new }
+        let(:options) { default_options.merge(data_mapper: data_mapper) }
+
+        it 'uses the provided data_mapper' do
+          mock(data_mapper).get_models(anything) { [] }
+          subject.execute(Workspace.unscoped)
+        end
+      end
     end
   end
 end