Fix: Add '| 0' type union for flags enums without zero value member

Author: diegomvh

projects/angular-odata/schematics/apigen/angular/entity.ts

@@ -28,6 +28,9 @@ export class EntityProperty {
     if (enumType !== undefined) {
       type = enumType.importedName(imports)!;
       type += this.edmType.Collection ? '[]' : '';
+      if (!this.edmType.Collection && enumType.isFlags() && !enumType.hasValue(0)) {
+        type += ' | 0';
+      }
     } else if (entityType !== undefined) {
       type = entityType.importedName(imports)!;
       type += this.edmType.Collection ? '[]' : '';

projects/angular-odata/schematics/apigen/angular/enum.ts

@@ -47,9 +47,12 @@ export class Enum extends Base {
   public members() {
     return this.edmType.Member.map((m) => `${m.Name} = ${m.Value}`);
   }
-  public flags() {
+  public isFlags() {
     return this.edmType.IsFlags;
   }
+  public hasValue(value: number) {
+    return this.edmType.Member.some(m => m.Value === value);
+  }
   public override importTypes(): string[] {
     return [];
   }

projects/angular-odata/schematics/apigen/angular/model.ts

@@ -30,6 +30,9 @@ export class ModelField {
     if (enumType !== undefined) {
       type = enumType.importedName(imports)!;
       type += this.edmType.Collection ? '[]' : '';
+      if (!this.edmType.Collection && enumType.isFlags() && !enumType.hasValue(0)) {
+        type += ' | 0';
+      }
     } else if (entityType !== undefined) {
       if (this.edmType.Collection) {
         const collection = pkg.findCollection(this.edmType.Type);