Resolve encoding issues with arrays of hstore (bug 11135).

We didn't have enough encoding for the wire protocol to store an array
of hstore types. So, further encode any hstore that is an array member.
Whilst we're here, ensure it's an HashWithIndifferentAccess being
returned, to be consistent with other serialized forms, and add testing
for arrays of hstore.

So now the following migration:

  enable_extension "hstore"
  create_table :servers do |t|
    t.string  :name
    t.hstore  :interfaces, array: true
  end

produces a model that can used like this, to store an array of hashes:

  server = Server.create(name: "server01", interfaces: [
    { name: "bge0", ipv4: "192.0.2.2", state: "up" },
    { name: "de0", state: "disabled", by: "misha" },
    { name: "fe0", state: "up" },
  ])

More at http://inopinatus.org/2013/07/12/using-arrays-of-hstore-with-rails-4/

activerecord/CHANGELOG.md

+*   Perform necessary deeper encoding when hstore is inside an array.
+
+    Fixes #11135.
+
+    *Josh Goodall*, *Genadi Samokovarov*
+
 *   Properly detect if a connection is still active before using it
     in multi-threaded environments.
 

activerecord/lib/active_record/connection_adapters/postgresql/cast.rb

@@ -35,11 +35,11 @@ def string_to_bit(value)
           end
         end
 
-        def hstore_to_string(object)
+        def hstore_to_string(object, array_member = false)
           if Hash === object
-            object.map { |k,v|
-              "#{escape_hstore(k)}=>#{escape_hstore(v)}"
-            }.join ','
+            string = object.map { |k, v| "#{escape_hstore(k)}=>#{escape_hstore(v)}" }.join(',')
+            string = escape_hstore(string) if array_member
+            string
           else
             object
           end
@@ -49,10 +49,10 @@ def string_to_hstore(string)
           if string.nil?
             nil
           elsif String === string
-            Hash[string.scan(HstorePair).map { |k,v|
+            Hash[string.scan(HstorePair).map { |k, v|
               v = v.upcase == 'NULL' ? nil : v.gsub(/\A"(.*)"\Z/m,'\1').gsub(/\\(.)/, '\1')
               k = k.gsub(/\A"(.*)"\Z/m,'\1').gsub(/\\(.)/, '\1')
-              [k,v]
+              [k, v]
             }]
           else
             string

activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb

@@ -121,7 +121,7 @@ def type_cast(value, column, array_member = false)
             end
           when Hash
             case column.sql_type
-            when 'hstore' then PostgreSQLColumn.hstore_to_string(value)
+            when 'hstore' then PostgreSQLColumn.hstore_to_string(value, array_member)
             when 'json' then PostgreSQLColumn.json_to_string(value)
             else super(value, column)
             end

activerecord/test/cases/adapters/postgresql/hstore_test.rb

@@ -24,6 +24,7 @@ def setup
     @connection.transaction do
       @connection.create_table('hstores') do |t|
         t.hstore 'tags', :default => ''
+        t.hstore 'payload', array: true
         t.hstore 'settings'
       end
     end
@@ -182,6 +183,30 @@ def test_select
       assert_equal({'1' => '2'}, x.tags)
     end
 
+    def test_array_cycle
+      assert_array_cycle([{"AA" => "BB", "CC" => "DD"}, {"AA" => nil}])
+    end
+
+    def test_array_strings_with_quotes
+      assert_array_cycle([{'this has' => 'some "s that need to be escaped"'}])
+    end
+
+    def test_array_strings_with_commas
+      assert_array_cycle([{'this,has' => 'many,values'}])
+    end
+
+    def test_array_strings_with_array_delimiters
+      assert_array_cycle(['{' => '}'])
+    end
+
+    def test_array_strings_with_null_strings
+      assert_array_cycle([{'NULL' => 'NULL'}])
+    end
+
+    def test_contains_nils
+      assert_array_cycle([{'NULL' => nil}])
+    end
+
     def test_select_multikey
       @connection.execute "insert into hstores (tags) VALUES ('1=>2,2=>3')"
       x = Hstore.first
@@ -237,6 +262,20 @@ def test_update_all
 
   private
 
+    def assert_array_cycle(array)
+      # test creation
+      x = Hstore.create!(payload: array)
+      x.reload
+      assert_equal(array, x.payload)
+
+      # test updating
+      x = Hstore.create!(payload: [])
+      x.payload = array
+      x.save!
+      x.reload
+      assert_equal(array, x.payload)
+    end
+
     def assert_cycle(hash)
       # test creation
       x = Hstore.create!(:tags => hash)