- Prefer defining field type value as a Symbol rather than a Class. (Symbol is already supported today.)

- Deprecate using field type as a Class.
- Add ability to define custom field types using a mini DSL (Mongoid::Fields.configure)

Author: johnnyshields

docs/reference/fields.txt

@@ -55,34 +55,40 @@ on a person by using the ``field`` macro.
 
    class Person
      include Mongoid::Document
-     field :name, type: String
-     field :date_of_birth, type: Date
-     field :weight, type: Float
+     field :name, type: :string
+     field :date_of_birth, type: :date
+     field :weight, type: :float
    end
 
 Below is a list of valid types for fields.
 
-- ``Array``
-- ``BigDecimal``
-- ``Boolean``
-- ``Date``
-- ``DateTime``
-- ``Float``
-- ``Hash``
-- ``Integer``
-- ``BSON::ObjectId``
-- ``BSON::Binary``
-- ``Range``
-- ``Regexp``
-- ``Set``
-- ``String``
-- ``StringifiedSymbol``
-- ``Symbol``
-- ``Time``
-- ``TimeWithZone``
+- ``:array``
+- ``:big_decimal``
+- ``:boolean``
+- ``:date``
+- ``:date_time``
+- ``:decimal128`` (uses ``BSON::Decimal128``)
+- ``:float``
+- ``:hash``
+- ``:integer``
+- ``:object_id`` (uses ``BSON::ObjectID``)
+- ``:binary`` (uses ``BSON::Binary``)
+- ``:range``
+- ``:regexp``
+- ``:set``
+- ``:string``
+- ``:stringified_symbol`` (see below)
+- ``:symbol``
+- ``:time``
+- ``:time_with_zone``
 
 To define custom field types, refer to :ref:`Custom Field Types <custom-field-types>` below.
 
+As of Mongoid 7.5, ``field :type`` should be specified as a ``Symbol``.
+Specifying as a ``Class`` is deprecated and will be no longer supported in a
+future major version of Mongoid. Unrecognized field type symbols will result
+in an `InvalidFieldType` error when the model class is loaded.
+
 
 .. _omitting-field-type-definition:
 
@@ -117,16 +123,16 @@ Types that are not supported as dynamic attributes since they cannot be cast are
 
 .. _field-type-stringified-symbol:
 
-Field Type: StringifiedSymbol
------------------------------
+Field Type :stringified_symbol
+------------------------------
 
-The ``StringifiedSymbol`` field type is the recommended field type for storing
-values that should be exposed as symbols to Ruby applications. When using the ``Symbol`` field type,
+The ``:stringified_symbol`` field type is the recommended field type for storing
+values that should be exposed as symbols to Ruby applications. When using the ``:symbol`` field type,
 Mongoid defaults to storing values as BSON symbols. For more information on the
 BSON symbol type, see :ref:`here <field-type-symbol>`.
 However, the BSON symbol type is deprecated and is difficult to work with in programming languages
-without native symbol types, so the ``StringifiedSymbol`` type allows the use of symbols
-while ensuring interoperability with other drivers. The ``StringifiedSymbol`` type stores all data
+without native symbol types, so the ``:stringified_symbol`` type allows the use of symbols
+while ensuring interoperability with other drivers. The ``:stringified_symbol`` type stores all data
 on the database as strings, while exposing values to the application as symbols.
 
 An example usage is shown below:
@@ -171,15 +177,15 @@ migration from fields that currently store either strings or BSON symbols in the
 
 .. _field-type-symbol:
 
-Field Type: Symbol
+Field Type :symbol
 ------------------
 
-New applications should use the :ref:`StringifiedSymbol field type <field-type-stringified-symbol>`
-to store Ruby symbols in the database. The ``StringifiedSymbol`` field type
+New applications should use the :ref:`:stringified_symbol field type <field-type-stringified-symbol>`
+to store Ruby symbols in the database. The ``:stringified_symbol`` field type
 provides maximum compatibility with other applications and programming languages
 and has the same behavior in all circumstances.
 
-Mongoid also provides the deprecated ``Symbol`` field type for serializing
+Mongoid also provides the deprecated ``:symbol`` field type for serializing
 Ruby symbols to BSON symbols. Because the BSON specification deprecated the
 BSON symbol type, the `bson` gem will serialize Ruby symbols into BSON strings
 when used on its own. However, in order to maintain backwards compatibility
@@ -202,10 +208,10 @@ snippet in your project:
 
 .. _field-type-hash:
 
-Field Type: Hash
+Field Type :hash
 ----------------
 
-When using a field of type Hash, be wary of adhering to the
+When using a field of type ``:hash``, be wary of adhering to the
 `legal key names for mongoDB <http://docs.mongodb.org/manual/reference/limits/#naming-restrictions>`_,
 or else the values will not store properly.
 
@@ -214,7 +220,7 @@ or else the values will not store properly.
    class Person
      include Mongoid::Document
      field :first_name
-     field :url, type: Hash
+     field :url, type: :hash
 
      # will update the fields properly and save the values
      def set_vals
@@ -234,21 +240,21 @@ or else the values will not store properly.
 
 .. _field-type-time:
 
-Field Type: Time
+Field Type :time
 ----------------
 
-``Time`` fields store values as ``Time`` instances in the :ref:`configured
+``:time`` fields store values as ``Time`` instances in the :ref:`configured
 time zone <time-zones>`.
 
 ``Date`` and ``DateTime`` instances are converted to ``Time`` instances upon
-assignment to a ``Time`` field:
+assignment to a ``:time`` field:
 
 .. code-block:: ruby
 
   class Voter
     include Mongoid::Document
 
-    field :registered_at, type: Time
+    field :registered_at, type: :time
   end
 
   Voter.new(registered_at: Date.today)
@@ -260,10 +266,10 @@ local time, because the application was not configured to use UTC times.
 
 .. _field-type-date:
 
-Field Type: Date
+Field Type :date
 ----------------
 
-Mongoid allows assignment of values of several types to ``Date`` fields:
+Mongoid allows assignment of values of several types to ``:date`` fields:
 
 - ``Date`` - the provided date is stored as is.
 - ``Time``, ``DateTime``, ``ActiveSupport::TimeWithZone`` - the date component
@@ -281,20 +287,20 @@ As a date & time to date conversion is lossy (it discards the time component),
 especially if an application operates with times in different time zones it is
 recommended to explicitly convert ``String``, ``Time`` and ``DateTime``
 objects to ``Date`` objects before assigning the values to fields of type
-``Date``.
+``:date``.
 
 
 .. _field-type-date-time:
 
-Field Type: DateTime
+Field Type :date_time
 ---------------------
 
 MongoDB stores all times as UTC timestamps. When assigning a value to a
-``DateTime`` field, or when querying a ``DateTime`` field, Mongoid
+``:date_time`` field, or when querying a ``:date_time`` field, Mongoid
 converts the passed in value to a UTC ``Time`` before sending it to the
 MongoDB server.
 
-``Time``, ``ActiveSupport::TimeWithZone`` and ``DateTime`` objects embed
+``Time``, ``ActiveSupport::TimeWithZone``, and ``DateTime`` objects embed
 time zone information, and the value persisted is the specified moment in
 time, in UTC. When the value is retrieved, the time zone in which it is
 returned is defined by the :ref:`configured time zone settings <time-zones>`.
@@ -303,7 +309,7 @@ returned is defined by the :ref:`configured time zone settings <time-zones>`.
 
    class Ticket
      include Mongoid::Document
-     field :opened_at, type: DateTime
+     field :opened_at, type: :date_time
    end
 
    Mongoid.use_activesupport_time_zone = true
@@ -333,7 +339,7 @@ doing so, the integers/floats are assumed to be Unix timestamps (in UTC):
     ticket.opened_at
     # => Fri, 14 Dec 2018 16:12:54 +0000
 
-If a string is used as a ``DateTime`` field value, the behavior depends on
+If a ``String`` is used as a ``:date_time`` field value, the behavior depends on
 whether the string includes a time zone. If no time zone is specified,
 the :ref:`default Mongoid time zone <time-zones>` is used:
 
@@ -355,7 +361,7 @@ If a time zone is specified, it is respected:
 
 .. _field-type-regexp:
 
-Field Type: Regexp
+Field Type :regexp
 ------------------
 
 MongoDB supports storing regular expressions in documents, and querying using
@@ -366,7 +372,7 @@ fork of `Oniguruma regular expression engine <https://github.com/kkos/oniguruma>
 The two regular expression implementations generally provide equivalent
 functionality but have several important syntax differences.
 
-When a field is declared to be of type Regexp, Mongoid converts Ruby regular
+When a field is declared to be of type ``:regexp``, Mongoid converts Ruby regular
 expressions to BSON regular expressions and stores the result in MongoDB.
 Retrieving the field from the database produces a ``BSON::Regexp::Raw``
 instance:
@@ -376,7 +382,7 @@ instance:
   class Token
     include Mongoid::Document
 
-    field :pattern, type: Regexp
+    field :pattern, type: :regexp
   end
 
   token = Token.create!(pattern: /hello.world/m)
@@ -747,9 +753,20 @@ can use in our model class as follows:
 
   class Profile
     include Mongoid::Document
-    field :location, type: Point
+    field :location, type: :point
+  end
+
+First, declare the new field type mapping in an initializer:
+
+.. code-block:: ruby
+
+  # in /config/initializers/mongoid_custom_fields.rb
+
+  Mongoid::Fields.configure do
+    type :point, Point
   end
 
+
 Then make a Ruby class to represent the type. This class must define methods
 used for MongoDB serialization and deserialization as follows:
 
@@ -845,8 +862,10 @@ specifiying its handler function as a block:
 
   # in /config/initializers/mongoid_custom_fields.rb
 
-  Mongoid::Fields.option :required do |model, field, value|
-    model.validates_presence_of field if value
+  Mongoid::Fields.configure do
+    option :required do |model, field, value|
+      model.validates_presence_of field if value
+    end
   end
 
 Then, use it your model class:

docs/release-notes/mongoid-7.5.txt

@@ -159,3 +159,40 @@ Mongoid 7.4 output:
 
 Notice that in 7.4 ``attribute_was(:age)`` returns the old attribute value,
 while in 7.5 ``attribute_was(:age)`` returns the new value.
+
+
+Setting Field Type as a Class is Deprecated
+-------------------------------------------
+
+Mongoid has historically supported defining the ``field :type`` option
+as either a Symbol or a Class. As of Mongoid 7.5, using a Class is deprecated
+and Symbol is preferred. Support for ``field :type`` as a Class will be
+removed in a future major version of Mongoid.
+
+.. code-block:: ruby
+
+  class Person
+    include Mongoid::Document
+
+    # Deprecated; will log an warning message.
+    field :first_name, type: String
+
+    # Good
+    field :last_name, type: :string
+  end
+
+
+Support for Defining Custom Field Type Values
+---------------------------------------------
+
+Mongoid 7.5 adds the ability to define custom ``field :type`` Symbol values as follows:
+
+.. code-block:: ruby
+
+  # in /config/initializers/mongoid_custom_fields.rb
+
+  Mongoid::Fields.configure do
+    type :point, Point
+  end
+
+Refer to the :ref:`docs <http://docs.mongodb.org/manual/reference/fields/#custom-field-types>` for details.

lib/config/locales/en.yml

@@ -172,15 +172,33 @@ en:
           resolution: "When defining the field :%{name} on '%{klass}', please provide
             valid options for the field. These are currently: %{valid}. If you
             meant to define a custom field option, please do so first as follows:\n\n
-            \_\_Mongoid::Fields.option :%{option} do |model, field, value|\n
-            \_\_\_\_# Your logic here...\n
+            \_\_Mongoid::Fields.configure do\n
+            \_\_\_\_option :%{option} do |model, field, value|\n
+            \_\_\_\_\_\_# Your logic here...\n
+            \_\_\_\_end\n
             \_\_end\n
             \_\_class %{klass}\n
             \_\_\_\_include Mongoid::Document\n
             \_\_\_\_field :%{name}, %{option}: true\n
             \_\_end\n\n
             Refer to:
             https://docs.mongodb.com/mongoid/current/reference/fields/#custom-field-options"
+        invalid_field_type:
+          message: "Invalid field type :%{type} for field :%{field} on model '%{klass}'."
+          summary: "Model '%{klass}' defines a field :%{field} with an unknown :type value
+            :%{type}. This value is neither present in Mongoid's default type mapping,
+            nor defined in a custom field type mapping."
+          resolution: "Please provide a valid :type value for the field. If you
+            meant to define a custom field type, please do so first as follows:\n\n
+            \_\_Mongoid::Fields.configure do\n
+            \_\_\_\_type :%{type}, YourTypeClass
+            \_\_end\n
+            \_\_class %{klass}\n
+            \_\_\_\_include Mongoid::Document\n
+            \_\_\_\_field :%{field}, type: :%{type}\n
+            \_\_end\n\n
+            Refer to:
+            https://docs.mongodb.com/mongoid/current/reference/fields/#custom-field-types"
         invalid_includes:
           message: "Invalid includes directive: %{klass}.includes(%{args})"
           summary: "Eager loading in Mongoid only supports providing arguments

lib/mongoid/errors.rb

@@ -15,6 +15,7 @@
 require "mongoid/errors/invalid_dependent_strategy"
 require "mongoid/errors/invalid_field"
 require "mongoid/errors/invalid_field_option"
+require "mongoid/errors/invalid_field_type"
 require "mongoid/errors/invalid_find"
 require "mongoid/errors/invalid_includes"
 require "mongoid/errors/invalid_index"

lib/mongoid/errors/invalid_field_type.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+module Mongoid
+  module Errors
+
+    # This error is raised when trying to define a field using a :type option value
+    # that is not present in the field type mapping.
+    class InvalidFieldType < MongoidError
+
+      # Create the new error.
+      #
+      # @example Instantiate the error.
+      #   InvalidFieldType.new('Person', 'first_name', 'stringgy')
+      #
+      # @param [ String ] klass The model class.
+      # @param [ String ] field The field on which the invalid type is used.
+      # @param [ String ] type The value of the field :type option.
+      def initialize(klass, field, type)
+        super(
+          compose_message('invalid_field_type', { klass: klass, field: field, type: type })
+        )
+      end
+    end
+  end
+end