fix for GRAILS-8815 "Domain hasMany association using a List is addin…

…g duplicate items when the parent is saved"

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

@@ -888,16 +888,18 @@ else if (association.doesCascade(CascadeType.PERSIST)) {
                                         Object inverseEntity = entityAccess.getProperty(association.getName());
                                         if (inverseEntity != null) {
                                             EntityAccess inverseAccess = createEntityAccess(association.getAssociatedEntity(), inverseEntity);
+                                            Object entity = entityAccess.getEntity();
                                             if (inverse instanceof OneToMany) {
                                                 Collection existingValues = (Collection) inverseAccess.getProperty(inverse.getName());
                                                 if (existingValues == null) {
                                                     existingValues = MappingUtils.createConcreteCollection(inverse.getType());
                                                     inverseAccess.setProperty(inverse.getName(), existingValues);
                                                 }
-                                                existingValues.add(entityAccess.getEntity());
+                                                if(!existingValues.contains(entity))
+                                                    existingValues.add(entity);
                                             }
                                             else if (inverse instanceof ToOne) {
-                                                inverseAccess.setProperty(inverse.getName(), entityAccess.getEntity());
+                                                inverseAccess.setProperty(inverse.getName(), entity);
                                             }
                                         }
                                     }

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

@@ -0,0 +1,64 @@
+package org.grails.datastore.gorm
+
+import spock.lang.Specification
+import spock.lang.Issue
+import grails.persistence.Entity
+import grails.gorm.tests.GormDatastoreSpec
+
+/**
+ */
+class AutoLinkOneToManyAssociationSpec extends GormDatastoreSpec{
+
+    @Issue('GRAILS-8815')
+    void "Test that associations are linked automatically when saving"() {
+        given:"A new domain class with a one-to-many association"
+        def author = new AutoLinkListAuthor(firstName:'foo', lastName: 'bar')
+        when:"The domain is saved"
+        author.save()
+        then:"The association is intially empty"
+        author.id != null
+        author.books == null
+
+        when:"An associated object is added"
+        def book1 = new AutoLinkListBook(title: 'grails', price: 43, published: new Date(), author: author)
+
+        // add the book to the author to complete the other side
+        author.addToBooks(book1)
+        then:"The relationship size is correct"
+        author.books.size() == 1
+
+        when:"The domain is saved"
+        author.save()
+        then:"The relationship size is still correct"
+        author.books.size() == 1
+    }
+
+    @Override
+    List getDomainClasses() {
+        [AutoLinkListAuthor,AutoLinkListBook]
+    }
+
+
+}
+
+@Entity
+class AutoLinkListAuthor {
+    Long id
+    String firstName
+    String lastName
+
+    // Hi, see here!
+    List books
+
+    static hasMany = [books: AutoLinkListBook]
+}
+
+@Entity
+class AutoLinkListBook {
+    Long id
+    String title
+    Date published
+    BigDecimal price
+
+    static belongsTo = [author: AutoLinkListAuthor]
+}