Use default class property for @optional injected properties

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 
 ### Fixed
+property injection tagged as @optional no longer overrides default values with `undefined`. 
 
 ## [6.0.2]
 

src/resolution/instantiation.ts

@@ -68,7 +68,9 @@ function createInstanceWithInjections<T>(
   args.propertyRequests.forEach((r: interfaces.Request, index: number) => {
     const property = r.target.identifier;
     const injection = args.propertyInjections[index];
-    (instance as Record<string | symbol, unknown>)[property] = injection;
+    if (!r.target.isOptional() || injection !== undefined) {
+      (instance as Record<string | symbol, unknown>)[property] = injection;
+    }
   });
   return instance
 }

test/annotation/optional.test.ts

@@ -107,4 +107,49 @@ describe('@optional', () => {
 
   });
 
+  it("Should allow to set a default value for class property dependencies flagged as optional", () => {
+    @injectable()
+    class Katana {
+      public name: string;
+      public constructor() {
+        this.name = 'Katana';
+      }
+    }
+
+    @injectable()
+    class Shuriken {
+      public name: string;
+      public constructor() {
+        this.name = 'Shuriken';
+      }
+    }
+
+    @injectable()
+    class Ninja {
+      public name: string = "Ninja";
+      @inject("Katana") public katana?: Katana;
+      @inject("Shuriken") @optional() public shuriken: Shuriken = {
+        name: "DefaultShuriken",
+      };
+    }
+
+    const container = new Container();
+
+    container.bind<Katana>('Katana').to(Katana);
+    container.bind<Ninja>('Ninja').to(Ninja);
+
+    let ninja = container.get<Ninja>('Ninja');
+    expect(ninja.name).to.eql('Ninja');
+    expect(ninja.katana?.name).to.eql('Katana');
+    expect(ninja.shuriken.name).to.eql('DefaultShuriken');
+
+    container.bind<Shuriken>('Shuriken').to(Shuriken);
+
+    ninja = container.get<Ninja>('Ninja');
+    expect(ninja.name).to.eql('Ninja');
+    expect(ninja.katana?.name).to.eql('Katana');
+    expect(ninja.shuriken.name).to.eql('Shuriken');
+    }
+  );
+
 });

wiki/optional_dependencies.md

@@ -84,3 +84,13 @@ class Ninja {
     }
 }
 ```
+
+Or using properties injection: 
+```ts
+@injectable()
+class Ninja {
+    public name = "Ninja";
+    @inject("Katana") public katana: Katana;
+    @inject("Shuriken") @optional() public shuriken: Shuriken = { name: "DefaultShuriken" } // Default value!
+}
+```