Breaking change: Remove custom timestamp feature

A little over four years ago, a feature was added to allow users
to change the name of the `versions.created_at` column. No reason
was given at the time.

#129

There are three reasons why this should not be configurable:

1. The standard column name in rails is `created_at`.
2. The majority of the `versions` table is, and should be, an
   implementation detail of PT.
3. This configuration option added moderate complexity to the
   library, and severe complexity to the test suite.

CHANGELOG.md

@@ -7,7 +7,8 @@ recommendations of [keepachangelog.com](http://keepachangelog.com/).
 
 ### Breaking Changes
 
-- None
+- `timestamp_field=` removed without replacement. It is no longer configurable. The
+  timestamp field in the `versions` table must now be named `created_at`.
 
 ### Deprecated
 

lib/paper_trail.rb

@@ -72,14 +72,12 @@ def enabled_for_model?(model)
 
     # Set the field which records when a version was created.
     # @api public
-    def timestamp_field=(field_name)
-      PaperTrail.config.timestamp_field = field_name
-    end
-
-    # Returns the field which records when a version was created.
-    # @api public
-    def timestamp_field
-      PaperTrail.config.timestamp_field
+    def timestamp_field=(_field_name)
+      raise(
+        "PaperTrail.timestamp_field= has been removed, without replacement. " \
+          "It is no longer configurable. The timestamp field in the versions table " \
+          "must now be named created_at."
+      )
     end
 
     # Sets who is responsible for any changes that occur. You would normally use

lib/paper_trail/cleaner.rb

@@ -52,7 +52,7 @@ def gather_versions(item_id = nil, date = :all)
     # versions.
     # @api private
     def group_versions_by_date(versions)
-      versions.group_by { |v| v.send(PaperTrail.timestamp_field).to_date }
+      versions.group_by { |v| v.created_at.to_date }
     end
   end
 end

lib/paper_trail/config.rb

@@ -6,7 +6,7 @@ module PaperTrail
   # configuration can be found in `paper_trail.rb`, others in `controller.rb`.
   class Config
     include Singleton
-    attr_accessor :timestamp_field, :serializer, :version_limit
+    attr_accessor :serializer, :version_limit
     attr_writer :track_associations
 
     def initialize
@@ -15,7 +15,6 @@ def initialize
       @enabled = true
 
       # Variables which affect all threads, whose access is *not* synchronized.
-      @timestamp_field = :created_at
       @serializer = PaperTrail::Serializers::YAML
     end
 

lib/paper_trail/record_history.rb

@@ -26,7 +26,7 @@ def sequence
         @versions.select(primary_key).order(primary_key.asc)
       else
         @versions.
-          select([timestamp, primary_key]).
+          select([table[:created_at], primary_key]).
           order(@version_class.timestamp_sort_order)
       end
     end
@@ -45,13 +45,5 @@ def primary_key
     def table
       @version_class.arel_table
     end
-
-    # @return - Arel::Attribute - Attribute representing the timestamp column
-    #   of the version table, usually named `created_at` (the rails convention)
-    #   but not always.
-    # @api private
-    def timestamp
-      table[PaperTrail.timestamp_field]
-    end
   end
 end

lib/paper_trail/record_trail.rb

@@ -170,7 +170,7 @@ def record_create
         whodunnit: PaperTrail.whodunnit
       }
       if @record.respond_to?(:updated_at)
-        data[PaperTrail.timestamp_field] = @record.updated_at
+        data[:created_at] = @record.updated_at
       end
       if record_object_changes? && changed_notably?
         data[:object_changes] = recordable_object_changes
@@ -220,7 +220,7 @@ def record_update(force)
           whodunnit: PaperTrail.whodunnit
         }
         if @record.respond_to?(:updated_at)
-          data[PaperTrail.timestamp_field] = @record.updated_at
+          data[:created_at] = @record.updated_at
         end
         if record_object_changes?
           data[:object_changes] = recordable_object_changes
@@ -376,9 +376,7 @@ def version_at(timestamp, reify_options = {})
     # Returns the objects (not Versions) as they were between the given times.
     def versions_between(start_time, end_time)
       versions = send(@record.class.versions_association_name).between(start_time, end_time)
-      versions.collect { |version|
-        version_at(version.send(PaperTrail.timestamp_field))
-      }
+      versions.collect { |version| version_at(version.created_at) }
     end
 
     # Executes the given method or block without creating a new version.

lib/paper_trail/version_concern.rb

@@ -74,8 +74,8 @@ def subsequent(obj, timestamp_arg = false)
           return where(arel_table[primary_key].gt(obj.id)).order(arel_table[primary_key].asc)
         end
 
-        obj = obj.send(PaperTrail.timestamp_field) if obj.is_a?(self)
-        where(arel_table[PaperTrail.timestamp_field].gt(obj)).order(timestamp_sort_order)
+        obj = obj.send(:created_at) if obj.is_a?(self)
+        where(arel_table[:created_at].gt(obj)).order(timestamp_sort_order)
       end
 
       # Returns versions before `obj`.
@@ -90,22 +90,22 @@ def preceding(obj, timestamp_arg = false)
           return where(arel_table[primary_key].lt(obj.id)).order(arel_table[primary_key].desc)
         end
 
-        obj = obj.send(PaperTrail.timestamp_field) if obj.is_a?(self)
-        where(arel_table[PaperTrail.timestamp_field].lt(obj)).
+        obj = obj.send(:created_at) if obj.is_a?(self)
+        where(arel_table[:created_at].lt(obj)).
           order(timestamp_sort_order("desc"))
       end
 
       def between(start_time, end_time)
         where(
-          arel_table[PaperTrail.timestamp_field].gt(start_time).
-          and(arel_table[PaperTrail.timestamp_field].lt(end_time))
+          arel_table[:created_at].gt(start_time).
+          and(arel_table[:created_at].lt(end_time))
         ).order(timestamp_sort_order)
       end
 
       # Defaults to using the primary key as the secondary sort order if
       # possible.
       def timestamp_sort_order(direction = "asc")
-        [arel_table[PaperTrail.timestamp_field].send(direction.downcase)].tap do |array|
+        [arel_table[:created_at].send(direction.downcase)].tap do |array|
           array << arel_table[primary_key].send(direction.downcase) if primary_key_is_int?
         end
       end

test/test_helper.rb

@@ -88,19 +88,6 @@ def assert_changes_equal(expected, actual)
   end
 end
 
-#
-# Helpers
-#
-
-def change_schema
-  ActiveRecord::Migration.verbose = false
-  ActiveRecord::Schema.define do
-    add_column :versions, :custom_created_at, :datetime
-  end
-  ActiveRecord::Migration.verbose = true
-  reset_version_class_column_info!
-end
-
 # Wrap args in a hash to support the ActionController::TestCase and
 # ActionDispatch::Integration HTTP request method switch to keyword args
 # (see https://github.com/rails/rails/blob/master/actionpack/CHANGELOG.md)
@@ -111,17 +98,3 @@ def params_wrapper(args)
     args
   end
 end
-
-def reset_version_class_column_info!
-  PaperTrail::Version.connection.schema_cache.clear!
-  PaperTrail::Version.reset_column_information
-end
-
-def restore_schema
-  ActiveRecord::Migration.verbose = false
-  ActiveRecord::Schema.define do
-    remove_column :versions, :custom_created_at
-  end
-  ActiveRecord::Migration.verbose = true
-  reset_version_class_column_info!
-end

test/unit/cleaner_test.rb

@@ -148,41 +148,4 @@ def populate_db!
       end
     end
   end # clean_versions! method
-
-  context "Custom timestamp field" do
-    setup do
-      change_schema
-      populate_db!
-      # now mess with the timestamps
-      @animals.each do |animal|
-        animal.versions.reverse.each_with_index do |version, index|
-          version.update_attribute(:custom_created_at, Time.now.utc + index.days)
-        end
-      end
-      PaperTrail.timestamp_field = :custom_created_at
-      @animals.map { |a| a.versions.reload } # reload the `versions` association for each animal
-    end
-
-    teardown do
-      PaperTrail.timestamp_field = :created_at
-      restore_schema
-    end
-
-    should "Baseline" do
-      assert_equal 9, PaperTrail::Version.count
-      @animals.each do |animal|
-        assert_equal 3, animal.versions.size
-        animal.versions.each_cons(2) do |a, b|
-          assert_equal a.created_at.to_date, b.created_at.to_date
-          assert_not_equal a.custom_created_at.to_date, b.custom_created_at.to_date
-        end
-      end
-    end
-
-    should "group by `PaperTrail.timestamp_field` when seperating the versions by date to clean" do
-      assert_equal 9, PaperTrail::Version.count
-      PaperTrail.clean_versions!
-      assert_equal 9, PaperTrail::Version.count
-    end
-  end
 end

test/unit/inheritance_column_test.rb

@@ -27,14 +27,12 @@ class InheritanceColumnTest < ActiveSupport::TestCase
 
       # For some reason `@dog.versions` doesn't include the final `destroy` version.
       # Neither do `@dog.versions.scoped` nor `@dog.versions(true)` nor `@dog.versions.reload`.
-      dog_versions = PaperTrail::Version.where(item_id: @dog.id).
-        order(PaperTrail.timestamp_field)
+      dog_versions = PaperTrail::Version.where(item_id: @dog.id).order(:created_at)
       assert_equal 4, dog_versions.count
       assert_nil dog_versions.first.reify
       assert_equal %w(NilClass Dog Dog Dog), dog_versions.map { |v| v.reify.class.name }
 
-      cat_versions = PaperTrail::Version.where(item_id: @cat.id).
-        order(PaperTrail.timestamp_field)
+      cat_versions = PaperTrail::Version.where(item_id: @cat.id).order(:created_at)
       assert_equal 4, cat_versions.count
       assert_nil cat_versions.first.reify
       assert_equal %w(NilClass Cat Cat Cat), cat_versions.map { |v| v.reify.class.name }

test/unit/model_test.rb

@@ -517,16 +517,9 @@ class HasPaperTrailModelTest < ActiveSupport::TestCase
 
     context "after a column is removed from the record's schema" do
       setup do
-        change_schema
-        Widget.connection.schema_cache.clear!
-        Widget.reset_column_information
         @last = @widget.versions.last
       end
 
-      teardown do
-        restore_schema
-      end
-
       should "reify previous version" do
         assert_kind_of Widget, @last.reify
       end

test/unit/version_test.rb

@@ -3,17 +3,10 @@
 module PaperTrail
   class VersionTest < ActiveSupport::TestCase
     setup do
-      change_schema
       @animal = Animal.create
       assert Version.creates.present?
     end
 
-    teardown do
-      restore_schema
-      Animal.connection.schema_cache.clear!
-      Animal.reset_column_information
-    end
-
     context ".creates" do
       should "return only create events" do
         Version.creates.each do |version|