fix(pinia-orm): Uncaught TypeError: parent.$fields()[key] is undefied when inserting nested data with polymorphic relationships

packages/pinia-orm/src/schema/Schema.ts

@@ -113,7 +113,8 @@ export class Schema {
       // If the `key` is not `null`, that means this record is a nested
       // relationship of the parent model. In this case, we'll attach any
       // missing foreign keys to the record first.
-      if (key !== null) { (parent.$fields()[key] as Relation).attach(parentRecord, record) }
+      console.log('schema', parent.$fields(), key, model.$entity(), parent.$entity())
+      if (key !== null) { (parent.$fields()[key] as Relation)?.attach(parentRecord, record) }
 
       // Next, we'll generate any missing primary key fields defined as
       // uid field.

packages/pinia-orm/tests/feature/relations/morph_many_save.spec.ts

@@ -122,4 +122,107 @@ describe('feature/relations/morph_many_save', () => {
       }
     })
   })
+
+  it('can save complicated polymorphs', () => {
+    Model.clearRegistries()
+    class Comment extends Model {
+      static entity = 'comments'
+      static fields () {
+        return {
+          id: this.number(0),
+          url: this.string(''),
+          content_id: this.number(0),
+          content_type: this.string(''),
+          content: this.morphTo([Video, Post], 'content_id', 'content_type'),
+          creator_id: this.string(null),
+          creator: this.belongsTo(Person, 'creator_id')
+        }
+      }
+    }
+
+    class Person extends Model {
+      static entity = 'person'
+      static primaryKey = 'id'
+
+      static fields () {
+        return {
+          id: this.uid(),
+          job: this.attr(''),
+          comments: this.hasMany(Comment, 'creator_id')
+        }
+      }
+    }
+
+    class Video extends Model {
+      static entity = 'videos'
+      static fields () {
+        return {
+          id: this.number(0),
+          link: this.string(''),
+          comments: this.morphMany(Comment, 'content_id', 'content_type')
+        }
+      }
+    }
+    class Post extends Model {
+      static entity = 'posts'
+      static fields () {
+        return {
+          id: this.number(0),
+          title: this.string(''),
+          comments: this.morphMany(Comment, 'content_id', 'content_type')
+        }
+      }
+    }
+    const person = useRepo(Person)
+
+    person.save({
+      id: 'p',
+      job: 'dev',
+      comments: [
+        {
+          id: 1,
+          content_id: 4,
+          content_type: 'posts',
+          content: { id: 4, title: 'a post' },
+          creator_id: 'p'
+        },
+        {
+          id: 2,
+          content_id: 3,
+          content_type: 'videos',
+          content: { id: 3, link: 'test' },
+          creator_id: 'p'
+        }
+      ]
+    })
+
+    assertState({
+      posts: {
+        4: { id: 4, title: 'a post' }
+      },
+      videos: {
+        3: { id: 3, link: 'test' }
+      },
+      comments: {
+        1: {
+          id: 1,
+          url: '',
+          creator_id: 'p',
+          content_id: 4,
+          content_type: 'posts'
+        },
+        2: {
+          id: 2,
+          url: '',
+          creator_id: 'p',
+          content_id: 3,
+          content_type: 'videos'
+        }
+      },
+      person: {
+        p: { id: 'p', job: 'dev' }
+      }
+
+    })
+  })
 })