Add validator

.gitignore

@@ -6,3 +6,4 @@
 /pkg/
 /spec/reports/
 /tmp/
+Gemfile.lock

lib/validates_associated_with_context.rb

@@ -1,6 +1,4 @@
 # frozen_string_literal: true
 
 require_relative "validates_associated_with_context/version"
-
-module ValidatesAssociatedWithContext
-end
+require_relative "validates_associated_with_context/associated_with_context"

lib/validates_associated_with_context/associated_with_context.rb

@@ -0,0 +1,73 @@
+# frozen_string_literal: true
+
+module ValidatesAssociatedWithContext
+  class AssociatedWithContextValidator < ActiveModel::EachValidator # :nodoc:
+    attr_reader :context, :inherit_context
+
+    def initialize(options)
+      @context = options.delete(:context)
+      @inherit_context = options.delete(:inherit_context)
+
+      super
+    end
+
+    def validate_each(record, attribute, value)
+      validation_context = inherit_context ? record.validation_context : context
+
+      if Array(value).reject { |r| valid_object?(r, validation_context) }.any?
+        record.errors.add(attribute, :invalid, **options.merge(value: value))
+      end
+    end
+
+    private
+      def valid_object?(record, validation_context)
+        (record.respond_to?(:marked_for_destruction?) && record.marked_for_destruction?) || record.valid?(validation_context)
+      end
+  end
+
+  module ClassMethods
+    # Validates whether the associated object or objects are all valid.
+    # Works with any kind of association.
+    #
+    #   class Book < ActiveRecord::Base
+    #     has_many :pages
+    #     belongs_to :library
+    #
+    #     validates_associated_with_context :pages, :library
+    #   end
+    #
+    # WARNING: This validation must not be used on both ends of an association.
+    # Doing so will lead to a circular dependency and cause infinite recursion.
+    #
+    # NOTE: This validation will not fail if the association hasn't been
+    # assigned. If you want to ensure that the association is both present and
+    # guaranteed to be valid, you also need to use
+    # {validates_presence_of}[rdoc-ref:Validations::ClassMethods#validates_presence_of].
+    #
+    # Configuration options:
+    #
+    # * <tt>:context</tt> - The validation context to use.
+    # * <tt>:inherit_context</tt> - When <tt>true</tt>, the validation context
+    #   is passed to the associated model.
+    # * <tt>:message</tt> - A custom error message (default is: "is invalid").
+    # * <tt>:on</tt> - Specifies the contexts where this validation is active.
+    #   Runs in all validation contexts by default +nil+. You can pass a symbol
+    #   or an array of symbols. (e.g. <tt>on: :create</tt> or
+    #   <tt>on: :custom_validation_context</tt> or
+    #   <tt>on: [:create, :custom_validation_context]</tt>)
+    # * <tt>:if</tt> - Specifies a method, proc, or string to call to determine
+    #   if the validation should occur (e.g. <tt>if: :allow_validation</tt>,
+    #   or <tt>if: Proc.new { |user| user.signup_step > 2 }</tt>). The method,
+    #   proc or string should return or evaluate to a +true+ or +false+ value.
+    # * <tt>:unless</tt> - Specifies a method, proc, or string to call to
+    #   determine if the validation should not occur (e.g. <tt>unless: :skip_validation</tt>,
+    #   or <tt>unless: Proc.new { |user| user.signup_step <= 2 }</tt>). The
+    #   method, proc, or string should return or evaluate to a +true+ or +false+
+    #   value.
+    def validates_associated_with_context(*attr_names)
+      validates_with ValidatesAssociatedWithContext::AssociatedWithContextValidator, _merge_attributes(attr_names)
+    end
+  end
+end
+
+ActiveRecord::Validations::ClassMethods.include ValidatesAssociatedWithContext::ClassMethods