Fix misleading errors for has_one through relations

2 files changed, 24 insertions, 4 deletions

diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index 82cb3fed59..a830b0e0e4 100644
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -61,12 +61,18 @@ module ActiveRecord
     end
   end
 
-  class HasManyThroughCantAssociateThroughHasOneOrManyReflection < ActiveRecordError #:nodoc:
+  class ThroughCantAssociateThroughHasOneOrManyReflection < ActiveRecordError #:nodoc:
     def initialize(owner, reflection)
       super("Cannot modify association '#{owner.class.name}##{reflection.name}' because the source reflection class '#{reflection.source_reflection.class_name}' is associated to '#{reflection.through_reflection.class_name}' via :#{reflection.source_reflection.macro}.")
     end
   end
 
+  class HasManyThroughCantAssociateThroughHasOneOrManyReflection < ThroughCantAssociateThroughHasOneOrManyReflection #:nodoc:
+  end
+
+  class HasOneThroughCantAssociateThroughHasOneOrManyReflection < ThroughCantAssociateThroughHasOneOrManyReflection #:nodoc:
+  end
+
   class HasManyThroughCantAssociateNewRecords < ActiveRecordError #:nodoc:
     def initialize(owner, reflection)
       super("Cannot associate new records through '#{owner.class.name}##{reflection.name}' on '#{reflection.source_reflection.class_name rescue nil}##{reflection.source_reflection.name rescue nil}'. Both records must have an id in order to create the has_many :through record associating them.")
@@ -79,12 +85,18 @@ module ActiveRecord
     end
   end
 
-  class HasManyThroughNestedAssociationsAreReadonly < ActiveRecordError #:nodoc:
+  class ThroughNestedAssociationsAreReadonly < ActiveRecordError #:nodoc:
     def initialize(owner, reflection)
       super("Cannot modify association '#{owner.class.name}##{reflection.name}' because it goes through more than one other association.")
     end
   end
 
+  class HasManyThroughNestedAssociationsAreReadonly < ThroughNestedAssociationsAreReadonly #:nodoc:
+  end
+
+  class HasOneThroughNestedAssociationsAreReadonly < ThroughNestedAssociationsAreReadonly #:nodoc:
+  end
+
   class EagerLoadPolymorphicError < ActiveRecordError #:nodoc:
     def initialize(reflection)
       super("Cannot eagerly load the polymorphic association #{reflection.name.inspect}")
diff --git a/activerecord/lib/active_record/associations/through_association.rb b/activerecord/lib/active_record/associations/through_association.rb
index 55ee9f04e0..d0ec3e8015 100644
--- a/activerecord/lib/active_record/associations/through_association.rb
+++ b/activerecord/lib/active_record/associations/through_association.rb
@@ -76,13 +76,21 @@ module ActiveRecord
 
         def ensure_mutable
           unless source_reflection.belongs_to?
-            raise HasManyThroughCantAssociateThroughHasOneOrManyReflection.new(owner, reflection)
+            if reflection.has_one?
+              raise HasOneThroughCantAssociateThroughHasOneOrManyReflection.new(owner, reflection)
+            else
+              raise HasManyThroughCantAssociateThroughHasOneOrManyReflection.new(owner, reflection)
+            end
           end
         end
 
         def ensure_not_nested
           if reflection.nested?
-            raise HasManyThroughNestedAssociationsAreReadonly.new(owner, reflection)
+            if reflection.has_one?
+              raise HasOneThroughNestedAssociationsAreReadonly.new(owner, reflection)
+            else
+              raise HasManyThroughNestedAssociationsAreReadonly.new(owner, reflection)
+            end
           end
         end