fix for GRAILS-8757 "In unit tests, back reference is not set for one…

…-to-one association"

grails-datastore-core/src/main/groovy/org/grails/datastore/mapping/engine/NativeEntryEntityPersister.java

@@ -823,6 +823,14 @@ else if (association.doesCascade(CascadeType.PERSIST)) {
                                 }
 
                                 if(association.doesCascade(CascadeType.PERSIST)) {
+
+                                    if(association.isBidirectional()) {
+                                        Association inverseSide = association.getInverseSide();
+                                        if(inverseSide != null) {
+                                            EntityAccess inverseAccess = new EntityAccess(inverseSide.getOwner(), associatedObject);
+                                            inverseAccess.setProperty(inverseSide.getName(), obj);
+                                        }
+                                    }
                                     associationPersister.persist(associatedObject);
                                 }
                             }

grails-datastore-gorm-test/src/test/groovy/org/grails/datastore/gorm/HasOneSetInverseSideSpec.groovy

@@ -0,0 +1,58 @@
+package org.grails.datastore.gorm
+
+import grails.persistence.Entity
+import spock.lang.Issue
+import grails.gorm.tests.GormDatastoreSpec
+
+/**
+ */
+class HasOneSetInverseSideSpec extends GormDatastoreSpec{
+
+    @Issue('GRAILS-8757')
+    void "Test that saving a one-to-one automatically sets the inverse side"() {
+        when:"A bidirectional one-to-one is saved"
+            def address = new HouseAddress(street:"Street 001")
+            def house = new House(name:"Some house", address: address)
+
+            house.save(flush:true)
+
+        then:"The inverse side is autmotically set"
+            house.id != null
+            address.house != null        
+
+        when:"The association is queried"
+            session.clear()
+            house = House.get(house.id)
+
+        then:"The data model is valid"
+            house.id != null
+            house.address != null
+            house.address.house != null
+
+
+    }
+
+    @Override
+    List getDomainClasses() {
+        [House, HouseAddress]
+    }
+
+
+}
+
+@Entity
+class House {
+    Long id
+    String name
+
+    HouseAddress address
+    static hasOne = [address: HouseAddress]
+}
+
+@Entity
+class HouseAddress {
+    Long id
+    String street
+
+    House house
+}