Errors can be indexed with nested attributes

`has_many` can now take `index_errors: true` as an
option.  When this is enabled, errors for nested models will be
returned alongside an index, as opposed to just the nested model name.
This option can also be enabled (or disabled) globally through
`ActiveRecord::Base.index_nested_attribute_errors`

E.X.

```ruby
class Guitar < ActiveRecord::Base
  has_many :tuning_pegs
  accepts_nested_attributes_for :tuning_pegs
end

class TuningPeg < ActiveRecord::Base
  belongs_to :guitar
  validates_numericality_of :pitch
end
```

 - Old style
 - `guitar.errors["tuning_pegs.pitch"] = ["is not a number"]`

 - New style (if defined globally, or set in has_many_relationship)
 - `guitar.errors["tuning_pegs[1].pitch"] = ["is not a number"]`

[Michael Probber, Terence Sun]

1 files changed, 9 insertions, 0 deletions

diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index 7b42f8a4a5..3d39f922f3 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -336,6 +336,10 @@ ActiveRecord::Schema.define do
     t.column :key, :string
   end
 
+  create_table :guitar, force: true do |t|
+    t.string :color
+  end
+
   create_table :inept_wizards, force: true do |t|
     t.column :name, :string, null: false
     t.column :city, :string, null: false
@@ -789,6 +793,11 @@ ActiveRecord::Schema.define do
     t.belongs_to :ship
   end
 
+  create_table :tuning_pegs, force: true do |t|
+    t.integer :guitar_id
+    t.float :pitch
+  end
+
   create_table :tyres, force: true do |t|
     t.integer :car_id
   end