Add support for custom indices

lib/shoulda/matchers/active_record/have_db_index_matcher.rb

@@ -72,8 +72,9 @@ def have_db_index(columns)
       # @private
       class HaveDbIndexMatcher
         def initialize(columns)
-          @columns = normalize_columns_to_array(columns)
-          @options = {}
+          @columns        = normalize_columns_to_array(columns)
+          @joined_columns = normalize_columns_to_string(columns)
+          @options        = {}
         end
 
         def unique(unique = true)
@@ -124,7 +125,10 @@ def correct_unique?
         end
 
         def matched_index
-          indexes.detect { |each| each.columns == @columns }
+          indexes.detect do |each|
+            each.columns == @columns ||
+              normalize_columns_to_string(each.columns) == @joined_columns
+          end
         end
 
         def model_class
@@ -154,6 +158,10 @@ def index_type
         def normalize_columns_to_array(columns)
           Array.wrap(columns).map(&:to_s)
         end
+
+        def normalize_columns_to_string(columns)
+          Array.wrap(columns).compact.map(&:to_s).join(', ')
+        end
       end
     end
   end

spec/unit/shoulda/matchers/active_record/have_db_index_matcher_spec.rb

@@ -24,6 +24,16 @@
   end
 
   context 'have_db_index on multiple columns' do
+    it 'accepts an existing index regardless of order' do
+      db_connection = create_table 'geocodings' do |table|
+        table.integer :geocodable_id
+        table.string  :geocodable_type
+      end
+      db_connection.add_index :geocodings, [:geocodable_type, :geocodable_id]
+      expect(define_model_class('Geocoding').new).
+        to have_db_index([:geocodable_id, :geocodable_type])
+    end
+
     it 'accepts an existing index' do
       db_connection = create_table 'geocodings' do |table|
         table.integer :geocodable_id
@@ -44,6 +54,43 @@
     end
   end
 
+  context 'with a custom sql index' do
+    it 'accepts an existing index' do
+      db_connection = create_table 'geocodings' do |table|
+        table.integer :geocodable_id
+        table.integer :geocodable_value
+      end
+
+      db_connection.execute(
+        <<-SQL
+          CREATE INDEX index_geocodings_on_geocodable_id_and_absolute_value
+            ON geocodings(geocodable_id, abs(geocodable_value));
+        SQL
+      )
+
+      expect(define_model_class('Geocoding').new).
+        to have_db_index(expected_indexed_columns)
+    end
+
+    it 'rejects a nonexistent index' do
+      create_table 'geocodings' do |table|
+        table.integer :geocodable_id
+        table.datetime :geocodable_at
+      end
+
+      expect(define_model_class('Geocoding').new).
+        not_to have_db_index(expected_indexed_columns)
+    end
+
+    def expected_indexed_columns
+      if postgresql?
+        [:geocodable_id, 'abs(geocodable_value)']
+      else
+        [:geocodable_id, nil]
+      end
+    end
+  end
+
   it 'join columns with and when describing multiple columns' do
     expect(have_db_index([:user_id, :post_id]).description).to match(/on columns user_id and post_id/)
   end