fix: Injecting a property with .then results in undefined (#1570)

CHANGELOG.md

@@ -11,7 +11,8 @@ 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`. 
+- property injection tagged as @optional no longer overrides default values with `undefined`. 
+- Injecting an object with a `.then` property which is not a promise no longer resolves to `undefined`.
 
 ## [6.0.2]
 

src/utils/async.ts

@@ -1,7 +1,7 @@
 function isPromise<T>(object: unknown): object is Promise<T> {
-  const isObjectOrFunction = (typeof object === 'object' && object !== null) || typeof object === 'function';
-
-  return isObjectOrFunction && typeof (object as PromiseLike<T>).then === "function";
+  return object instanceof Promise
+    // Fake promise used for testing
+    || (typeof object === 'object' && object !== null && (object as {_isFakePromise: string})._isFakePromise === 'IS_FAKE_PROMISE');
 }
 
 function isPromiseOrContainsPromise<T>(object: unknown): object is Promise<T> | (T | Promise<T>)[] {

test/bugs/issue_1570.test.ts

@@ -0,0 +1,26 @@
+import { expect } from "chai";
+import { Container, inject, injectable } from "../../src/inversify";
+
+describe("Issue 1570", () => {
+  it("It should not return injected value as undefined if the value contains a .then property but it is not a promise", () => {
+    const container = new Container();
+
+    interface Injected {
+      myProperty: string;
+      then: () => number;
+    }
+
+    @injectable()
+    class ResolveMe {
+      constructor(@inject("Injected") public injected: Injected) {}
+    }
+
+    container.bind("Injected").toConstantValue({
+      myProperty: "myNewProperty",
+      then: () => 1
+    });
+
+    const me = container.resolve(ResolveMe);
+    expect(me.injected.myProperty).to.eql("myNewProperty");
+  });
+});

test/resolution/resolver.test.ts

@@ -1460,8 +1460,10 @@ describe('Resolve', () => {
 
     @injectable()
     class PromiseLike {
+      _isFakePromise = 'IS_FAKE_PROMISE'
       public then() {
         return {
+          _isFakePromise: 'IS_FAKE_PROMISE',
           then: stub
         };
       }