Deprecate implicit eager loading. Closes #950.

6 files changed, 19 insertions, 5 deletions

diff --git a/activerecord/lib/active_record/associations/association_scope.rb b/activerecord/lib/active_record/associations/association_scope.rb
index 6f8b76abda..090f690f0d 100644
--- a/activerecord/lib/active_record/associations/association_scope.rb
+++ b/activerecord/lib/active_record/associations/association_scope.rb
@@ -20,7 +20,7 @@ module ActiveRecord
         # It's okay to just apply all these like this. The options will only be present if the
         # association supports that option; this is enforced by the association builder.
         scope = scope.apply_finder_options(options.slice(
-          :readonly, :include, :order, :limit, :joins, :group, :having, :offset, :select))
+          :readonly, :include, :eager_load, :order, :limit, :joins, :group, :having, :offset, :select))
 
         if options[:through] && !options[:include]
           scope = scope.includes(source_options[:include])
diff --git a/activerecord/lib/active_record/associations/builder/association.rb b/activerecord/lib/active_record/associations/builder/association.rb
index d4f59100e8..776f0d0469 100644
--- a/activerecord/lib/active_record/associations/builder/association.rb
+++ b/activerecord/lib/active_record/associations/builder/association.rb
@@ -1,7 +1,7 @@
 module ActiveRecord::Associations::Builder
   class Association #:nodoc:
     class_attribute :valid_options
-    self.valid_options = [:class_name, :foreign_key, :select, :conditions, :include, :extend, :readonly, :validate]
+    self.valid_options = [:class_name, :foreign_key, :select, :conditions, :include, :eager_load, :extend, :readonly, :validate]
 
     # Set by subclasses
     class_attribute :macro
diff --git a/activerecord/lib/active_record/associations/preloader/association.rb b/activerecord/lib/active_record/associations/preloader/association.rb
index 779f8164cc..298decb0f1 100644
--- a/activerecord/lib/active_record/associations/preloader/association.rb
+++ b/activerecord/lib/active_record/associations/preloader/association.rb
@@ -100,6 +100,7 @@ module ActiveRecord
 
           scope = scope.select(preload_options[:select] || options[:select] || table[Arel.star])
           scope = scope.includes(preload_options[:include] || options[:include])
+          scope = scope.eager_load(preload_options[:eager_load] || options[:eager_load])
 
           if options[:as]
             scope = scope.where(
diff --git a/activerecord/lib/active_record/associations/preloader/through_association.rb b/activerecord/lib/active_record/associations/preloader/through_association.rb
index ad6374d09a..97898c53ae 100644
--- a/activerecord/lib/active_record/associations/preloader/through_association.rb
+++ b/activerecord/lib/active_record/associations/preloader/through_association.rb
@@ -53,6 +53,7 @@ module ActiveRecord
           else
             if options[:conditions]
               through_options[:include]    = options[:include] || options[:source]
+              through_options[:eager_load] = options[:eager_load] || options[:source]
               through_options[:conditions] = options[:conditions]
             end
 
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 258c1959a0..bbadca84be 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 require 'active_support/core_ext/object/blank'
+require 'active_support/deprecation'
 
 module ActiveRecord
   # = Active Record Relation
@@ -521,7 +522,18 @@ module ActiveRecord
       # always convert table names to downcase as in Oracle quoted table names are in uppercase
       joined_tables = joined_tables.flatten.compact.map { |t| t.downcase }.uniq
 
-      (tables_in_string(to_sql) - joined_tables).any?
+      referenced_tables = (tables_in_string(to_sql) - joined_tables)
+      if referenced_tables.any?
+        ActiveSupport::Deprecation.warn(
+          "Your query appears to reference tables (#{referenced_tables.join(', ')}) that are not " \
+          "explicitly joined. This implicit joining is deprecated, so you must explicitly " \
+          "reference the tables. For example, instead of Author.includes(:posts).where(\"posts.name = 'foo'\"), " \
+          "you should write Author.eager_load(:posts).where(\"posts.name = 'foo'\")."
+        )
+        true
+      else
+        false
+      end
     end
 
     def tables_in_string(string)
diff --git a/activerecord/lib/active_record/relation/spawn_methods.rb b/activerecord/lib/active_record/relation/spawn_methods.rb
index ba882beca9..a5194beae5 100644
--- a/activerecord/lib/active_record/relation/spawn_methods.rb
+++ b/activerecord/lib/active_record/relation/spawn_methods.rb
@@ -113,7 +113,7 @@ module ActiveRecord
       result
     end
 
-    VALID_FIND_OPTIONS = [ :conditions, :include, :joins, :limit, :offset, :extend,
+    VALID_FIND_OPTIONS = [ :conditions, :include, :joins, :limit, :offset, :extend, :eager_load,
                            :order, :select, :readonly, :group, :having, :from, :lock ]
 
     def apply_finder_options(options)
@@ -124,7 +124,7 @@ module ActiveRecord
       finders = options.dup
       finders.delete_if { |key, value| value.nil? && key != :limit }
 
-      ([:joins, :select, :group, :order, :having, :limit, :offset, :from, :lock, :readonly] & finders.keys).each do |finder|
+      ([:joins, :select, :group, :order, :having, :limit, :offset, :from, :lock, :readonly, :eager_load] & finders.keys).each do |finder|
         relation = relation.send(finder, finders[finder])
       end