MONGOID-5608 - Allow exists? on relations

docs/release-notes/mongoid-9.0.txt

@@ -370,6 +370,12 @@ Bug Fixes and Improvements
 
 This section will be for smaller bug fixes and improvements:
 
+- The ``exists?`` method on relations now accepts the same arguments
+  as ``Criteria#exists?``.
+  `MONGOID-5608 <https://jira.mongodb.org/browse/MONGOID-5608>`_.
+- Calling ``exists?`` on an embedded relation nil now return ``false``
+  when the relation is not persisted in the database.
+  `MONGOID-5610 <https://jira.mongodb.org/browse/MONGOID-5610>`_.
 - The ``.tally`` method can now take a keyword arg :unwind
   which tallies array values individually (using the ``$unwind`` operator.)
   `MONGOID-5556 <https://jira.mongodb.org/browse/MONGOID-5556>`_.

lib/mongoid/association/embedded/embeds_many/proxy.rb

@@ -16,6 +16,8 @@ class EmbedsMany
         class Proxy < Association::Many
           include Batchable
 
+          def_delegator :criteria, :exists?
+
           # Appends a document or array of documents to the association. Will set
           # the parent and update the index in the process.
           #
@@ -212,21 +214,6 @@ def destroy_all(conditions = {})
             remove_all(conditions, :destroy)
           end
 
-          # Determine if any documents in this association exist in the database.
-          #
-          # @example Are there persisted documents?
-          #   person.posts.exists?
-          #
-          # @param [ Hash | Object | false ] id_or_conditions an _id to
-          #   search for, a hash of conditions, nil or false.
-          #
-          # @return [ true | false ] True is persisted documents exist, false if not.
-          def exists?(id_or_conditions = :none)
-            return _target.any?(&:persisted?) if id_or_conditions == :none
-
-            criteria.exists?(id_or_conditions)
-          end
-
           # Finds a document in this association through several different
           # methods.
           #

lib/mongoid/association/referenced/has_many/proxy.rb

@@ -14,7 +14,7 @@ class HasMany
         class Proxy < Association::Many
           extend Forwardable
 
-          def_delegator :criteria, :count
+          def_delegators :criteria, :count, :exists?
           def_delegators :_target, :first, :in_memory, :last, :reset, :uniq
 
           # Appends a document or array of documents to the association. Will set
@@ -163,26 +163,6 @@ def each(&block)
             end
           end
 
-          # Determine if any documents in this association exist in the database.
-          #
-          # If the association contains documents but all of the documents
-          # exist only in the application, i.e. have not been persisted to the
-          # database, this method returns false.
-          #
-          # This method queries the database on each invocation even if the
-          # association is already loaded into memory.
-          #
-          # @example Are there persisted documents?
-          #   person.posts.exists?
-          #
-          # @param [ Hash | Object | false ] id_or_conditions an _id to
-          #   search for, a hash of conditions, nil or false.
-          #
-          # @return [ true | false ] True is persisted documents exist, false if not.
-          def exists?(id_or_conditions = :none)
-            criteria.exists?(id_or_conditions)
-          end
-
           # Find the matching document on the association, either based on id or
           # conditions.
           #

lib/mongoid/contextual/memory.rb

@@ -116,14 +116,19 @@ def each(&block)
       # @example Do any documents exist for given conditions.
       #   context.exists?(name: "...")
       #
-      # @param [ Hash | Object | false ] id_or_conditions an _id to
-      #   search for, a hash of conditions, nil or false.
+      # @example Always return false.
+      #   context.exists?(false)
+      #
+      # @param [ :none | Hash | BSON::ObjectId | nil | false ] id_or_conditions
+      #   May optionally supply search conditions as a hash or an object id.
+      #   Will always return false when given nil or false. The symbol :none is
+      #   the default when argument is not supplied.
       #
       # @return [ true | false ] If the count is more than zero.
       #   Always false if passed nil or false.
       def exists?(id_or_conditions = :none)
         case id_or_conditions
-        when :none then any?
+        when :none then any?(&:persisted?)
         when nil, false then false
         when Hash then Memory.new(criteria.where(id_or_conditions)).exists?
         else Memory.new(criteria.where(_id: id_or_conditions)).exists?

lib/mongoid/contextual/mongo.rb

@@ -159,11 +159,16 @@ def each(&block)
       # @example Do any documents exist for given conditions.
       #   context.exists?(name: "...")
       #
+      # @example Always return false.
+      #   context.exists?(false)
+      #
       # @note We don't use count here since Mongo does not use counted
       #   b-tree indexes.
       #
-      # @param [ Hash | Object | false ] id_or_conditions an _id to
-      #   search for, a hash of conditions, nil or false.
+      # @param [ :none | Hash | BSON::ObjectId | nil | false ] id_or_conditions
+      #   May optionally supply search conditions as a hash or an object id.
+      #   Will always return false when given nil or false. The symbol :none is
+      #   the default when argument is not supplied.
       #
       # @return [ true | false ] If the count is more than zero.
       #   Always false if passed nil or false.

lib/mongoid/contextual/none.rb

@@ -57,7 +57,7 @@ def each(&block)
         end
       end
 
-      # Do any documents exist for the context.
+      # Do any documents exist for the null context.
       #
       # @example Do any documents exist in the null context.
       #   context.exists?
@@ -68,8 +68,11 @@ def each(&block)
       # @example Do any documents exist for given conditions.
       #   context.exists?(name: "...")
       #
-      # @param [ Hash | Object | false ] _id_or_conditions An _id to
-      #   search for, a hash of conditions, nil or false.
+      # @example Always return false.
+      #   context.exists?(false)
+      #
+      # @param [ :none | Hash | BSON::ObjectId | nil | false ] _id_or_conditions
+      #   Not used in null context.
       #
       # @return [ false ] Always false.
       def exists?(_id_or_conditions = :none)

lib/mongoid/contextual/queryable.rb

@@ -19,7 +19,7 @@ module Queryable
       #
       # @return [ true | false ] If the context is empty.
       def blank?
-        !exists?
+        !any?
       end
       alias_method :empty?, :blank?
     end

lib/mongoid/findable.rb

@@ -107,8 +107,13 @@ def empty?
     # @example Do any documents exist for given conditions.
     #   Person.exists?(name: "...")
     #
-    # @param [ Hash | Object | false ] id_or_conditions an _id to
-    #   search for, a hash of conditions, nil or false.
+    # @example Always return false.
+    #   context.exists?(false)
+    #
+    # @param [ :none | Hash | BSON::ObjectId | nil | false ] id_or_conditions
+    #   May optionally supply search conditions as a hash or an object id.
+    #   Will always return false when given nil or false. The symbol :none is
+    #   the default when argument is not supplied.
     #
     # @return [ true | false ] If any documents exist for the conditions.
     #   Always false if passed nil or false.