Unique constraint ignores transient group in parent/child save

[rmorrise]

Task List

• Steps to reproduce provided
• Example that reproduces the problem uploaded to Github
• Full description of the issue provided (see below)

Steps to Reproduce

1. Clone the example repo:
   https://github.com/rmorrise/grails-unique-child
2. grails run-app
3. POST the following JSON data:
   http://localhost:8080/MasterThing
Content-Type application/json

{
	"details": [
		{
			"itemName": "Foo"
		}
	]
}

4. Repeat the same POST request again.

Expected Behaviour

Both requests should be OK.

Validation of the unique constraint on DetailItem should be scoped to the master object that is being posted.

Actual Behaviour

HTTP error 422:
Property [itemName] of class [class grails.unique.child.DetailItem] with value [Foo] must be unique

The unique constraint is validated globally for the itemName properly only.

Environment Information

• Operating System: Windows 7 x64
• GORM Version: 6.1.10.RELEASE
• Grails Version (if using Grails): 3.3.8
• JDK Version: 1.8.0_121

Example Application

• https://github.com/rmorrise/grails-unique-child