feat: initialize nullable properties with null value (#7795)

packages/core/utils/src/dml/__tests__/entity-builder.spec.ts

@@ -236,6 +236,12 @@ describe("Entity builder", () => {
       expect(metaData.className).toEqual("User")
       expect(metaData.path).toEqual("User")
 
+      const userInstance = new User()
+      expect(userInstance.username).toEqual(null)
+
+      userInstance.username = "john"
+      expect(userInstance.username).toEqual("john")
+
       expect(metaData.filters).toEqual({
         softDeletable: {
           name: "softDeletable",
@@ -547,6 +553,12 @@ describe("Entity builder", () => {
 
       const metaData = MetadataStorage.getMetadataFromDecorator(User)
 
+      const userInstance = new User()
+      expect(userInstance.role).toEqual(null)
+
+      userInstance.role = "admin"
+      expect(userInstance.role).toEqual("admin")
+
       expect(metaData.className).toEqual("User")
       expect(metaData.path).toEqual("User")
 

packages/core/utils/src/dml/helpers/create-mikro-orm-entity.ts

@@ -158,6 +158,18 @@ export function createMikrORMEntity() {
     MikroORMEntity: EntityConstructor<any>,
     field: PropertyMetadata
   ) {
+    /**
+     * Here we initialize nullable properties with a null value
+     */
+    if (field.nullable) {
+      Object.defineProperty(MikroORMEntity.prototype, field.fieldName, {
+        value: null,
+        configurable: true,
+        enumerable: true,
+        writable: true,
+      })
+    }
+
     if (SPECIAL_PROPERTIES[field.fieldName]) {
       SPECIAL_PROPERTIES[field.fieldName](MikroORMEntity, field)
       return
@@ -188,12 +200,12 @@ export function createMikrORMEntity() {
         ? PrimaryKey({
             columnType: "text",
             type: "string",
-            nullable: field.nullable,
+            nullable: false,
           })
         : Property({
             columnType: "text",
             type: "string",
-            nullable: field.nullable,
+            nullable: false,
           })
 
       IdDecorator(MikroORMEntity.prototype, field.fieldName)
@@ -584,6 +596,7 @@ export function createMikrORMEntity() {
    */
   return function createEntity<T extends DmlEntity<any>>(entity: T): Infer<T> {
     class MikroORMEntity {}
+
     const { name, schema, cascades } = entity.parse()
     const { modelName, tableName } = parseEntityName(name)