Add where_object query to PaperTrail::Version.

lib/paper_trail/serializers/json.rb

@@ -12,6 +12,25 @@ def load(string)
       def dump(object)
         ActiveSupport::JSON.encode object
       end
+
+      # Returns a SQL condition to be used to match the given field and value in
+      # the serialized object.
+      def where_object_condition(arel_field, field, value)
+        # Convert to JSON to handle strings and nulls correctly.
+        json_value = value.to_json
+
+        # If the value is a number, we need to ensure that we find the next
+        # character too, which is either `,` or `}`, to ensure that searching
+        # for the value 12 doesn't yield false positives when the value is
+        # 123.
+        if value.is_a? Numeric
+          arel_field.matches("%\"#{field}\":#{json_value},%").
+            or(
+          arel_field.matches("%\"#{field}\":#{json_value}}%"))
+        else
+          arel_field.matches("%\"#{field}\":#{json_value}%")
+        end
+      end
     end
   end
 end

lib/paper_trail/serializers/yaml.rb

@@ -12,6 +12,12 @@ def load(string)
       def dump(object)
         ::YAML.dump object
       end
+
+      # Returns a SQL condition to be used to match the given field and value in
+      # the serialized object.
+      def where_object_condition(arel_field, field, value)
+        arel_field.matches("%\n#{field}: #{value}\n%")
+      end
     end
   end
 end

lib/paper_trail/version_concern.rb

@@ -68,6 +68,20 @@ def timestamp_sort_order(direction = 'asc')
         end
       end
 
+      # Performs an attribute search on the serialized object by invoking the
+      # identically-named method in the serializer being used.
+      def where_object(**args)
+        arel_field = arel_table[:object]
+
+        where_conditions = args.map do |field, value|
+          PaperTrail.serializer.where_object_condition(arel_field, field, value)
+        end.reduce do |condition1, condition2|
+          condition1.and(condition2)
+        end
+
+        where(where_conditions)
+      end
+
       def primary_key_is_int?
         @primary_key_is_int ||= columns_hash[primary_key].type == :integer
       rescue
@@ -190,7 +204,7 @@ def previous
 
     def index
       table = self.class.arel_table unless @index
-      @index ||= 
+      @index ||=
         if self.class.primary_key_is_int?
           sibling_versions.select(table[self.class.primary_key]).order(table[self.class.primary_key].asc).index(self)
         else

test/test_helper.rb

@@ -11,6 +11,7 @@ def using_mysql?
 
 require File.expand_path("../dummy/config/environment.rb",  __FILE__)
 require "rails/test_help"
+require 'minitest/mock'
 require 'shoulda'
 require 'ffaker'
 require 'database_cleaner' if using_mysql?

test/unit/serializers/json_test.rb

@@ -37,4 +37,37 @@ class JSONTest < ActiveSupport::TestCase
     end
   end
 
+  context '`where_object` class method' do
+    context "when value is a string" do
+      should 'construct correct WHERE query' do
+        sql = PaperTrail::Serializers::JSON.where_object_condition(
+          PaperTrail::Version.arel_table[:object], :arg1, "Val 1").
+          to_sql
+
+        assert sql.include?("LIKE '%\"arg1\":\"Val 1\"%'")
+      end
+    end
+
+    context "when value is `null`" do
+      should 'construct correct WHERE query' do
+        sql = PaperTrail::Serializers::JSON.where_object_condition(
+          PaperTrail::Version.arel_table[:object], :arg1, nil).
+          to_sql
+
+        assert sql.include?("LIKE '%\"arg1\":null%'")
+      end
+    end
+
+    context "when value is a number" do
+      should 'construct correct WHERE query' do
+        sql = PaperTrail::Serializers::JSON.where_object_condition(
+          PaperTrail::Version.arel_table[:object], :arg1, -3.5).
+          to_sql
+
+        assert_equal sql,
+          "(\"versions\".\"object\" LIKE '%\"arg1\":-3.5,%' OR "\
+            "\"versions\".\"object\" LIKE '%\"arg1\":-3.5}%')"
+      end
+    end
+  end
 end

test/unit/serializers/yaml_test.rb

@@ -37,4 +37,12 @@ class YamlTest < ActiveSupport::TestCase
     end
   end
 
+  context '`where_object` class method' do
+    should 'construct correct WHERE query' do
+      sql = PaperTrail::Serializers::YAML.where_object_condition(
+        PaperTrail::Version.arel_table[:object], :arg1, "Val 1").
+        to_sql
+      assert sql.include?("LIKE '%\narg1: Val 1\n%'")
+    end
+  end
 end

test/unit/version_test.rb

@@ -98,4 +98,34 @@ class PaperTrail::VersionTest < ActiveSupport::TestCase
       end
     end
   end
+
+  context "PaperTrail::Version.where_object" do
+    should "call `where_object` on the serializer" do
+      # Create some args to fake-query on.
+      args = { a: 1, b: "2", c: false, d: nil }
+      arel_field = PaperTrail::Version.arel_table[:object]
+
+      # Create a dummy value for us to return for each condition that can be
+      # chained together with other conditions with Arel's `and`.
+      chainable_dummy = arel_field.matches("")
+
+      # Mock a serializer to expect to receive `where_object_condition` with the
+      # correct args.
+      serializer = MiniTest::Mock.new
+      serializer.expect :where_object_condition, chainable_dummy, [arel_field, :a, 1]
+      serializer.expect :where_object_condition, chainable_dummy, [arel_field, :b, "2"]
+      serializer.expect :where_object_condition, chainable_dummy, [arel_field, :c, false]
+      serializer.expect :where_object_condition, chainable_dummy, [arel_field, :d, nil]
+
+      # Stub out PaperTrail.serializer to return our mock, and then make the
+      # query call.
+      PaperTrail.stub :serializer, serializer do
+        PaperTrail::Version.where_object(**args)
+      end
+
+      # Verify that our serializer mock received the correct
+      # `where_object_condition` calls.
+      assert serializer.verify
+    end
+  end
 end