MONGOID-5264 add :present option to localized fields (#5408)

* MONGOID-5264 add :present option to localize

* MONGOID-5264 change present? to localize_present?

* MONGOID-5264 add tests and fix present

* MONGOID-5264 add docs and release notes

* MONGOID-5264 potentially fix tests

* MONGOID-5264 fix docs

* MONGOID-5264 update the docstring

* MONGOID-5264 reset fallbacks after setting

* Update docs/reference/fields.txt

Co-authored-by: Oleg Pudeyev <39304720+p-mongo@users.noreply.github.com>

* MONGOID-5264 answer comments

* Update lib/mongoid/attributes.rb

Co-authored-by: Oleg Pudeyev <39304720+p-mongo@users.noreply.github.com>

Co-authored-by: Oleg Pudeyev <39304720+p-mongo@users.noreply.github.com>

Author: neilshweky

source/reference/fields.txt

@@ -1396,6 +1396,42 @@ You can get and set all the translations at once by using the corresponding ``_t
      { "en" => "Marvelous!", "de" => "Wunderbar!" }
 
 
+.. _present-fields:
+
+Localize ``:present`` Field Option
+----------------------------------
+
+Mongoid supports the ``:present`` option when creating a localized field:
+
+.. code-block:: ruby
+
+   class Product
+     include Mongoid::Document
+     field :description, localize: :present
+   end
+
+This option automatically removes ``blank`` values (i.e. those that return true
+for the ``blank?`` method) from the ``_translations`` hash:
+
+.. code-block:: ruby
+
+   I18n.default_locale = :en
+   product = Product.new
+   product.description = "Marvelous!"
+   I18n.locale = :de
+   product.description = "Fantastisch!"
+
+   product.description_translations
+   # { "en" => "Marvelous!", "de" => "Fantastisch!" }
+
+   product.description = ""
+   product.description_translations
+   # { "en" => "Marvelous!" }
+
+When the empty string is written for the ``:de`` locale, the ``"de"`` key is
+removed from the ``_translations`` hash instead of writing the empty string.
+
+
 Fallbacks
 ---------
 

source/release-notes/mongoid-8.1.txt

@@ -99,3 +99,20 @@ specific version:
 This is helpful for upgrading between versions. See the section on
 :ref:`Version Based Default Configuration <load-defaults>` for more details on
 how to use this feature to make upgrading between Mongoid versions easier.
+
+
+Added ``:present`` option to localized fields
+---------------------------------------------
+
+The ``:present`` option was added to localized fields for removing blank values
+from the ``_translations`` hash:
+
+.. code-block:: ruby
+
+   class Product
+     include Mongoid::Document
+     field :description, localize: :present
+   end
+
+See the section on :ref:`Localize :present Field Option <present-fields>` for
+more details on how these are used.