return false for Construct.isConstruct

Author: mrgrain

packages/aws-cdk-lib/core/lib/private/detached-construct.ts

@@ -2,6 +2,8 @@ import { Construct, IConstruct } from 'constructs';
 import type { ResourceEnvironment } from '../environment';
 import { UnscopedValidationError } from '../errors';
 
+const CONSTRUCT_SYM = Symbol.for('constructs.Construct');
+
 /**
  * Base class for detached constructs that throw UnscopedValidationError
  * when accessing node, env, or with() methods.
@@ -28,6 +30,14 @@ export abstract class DetachedConstruct extends Construct implements IConstruct
     Object.defineProperty(this, 'node', {
       get() { throw new UnscopedValidationError(errorMessage); },
     });
+
+    // Despite extending Construct, DetachedConstruct doesn't work like one.
+    // So we try to not pretend that this is a construct as much as possible.
+    Object.defineProperty(this, CONSTRUCT_SYM, {
+      value: false,
+      enumerable: false,
+      writable: false,
+    });
   }
 
   public get env(): ResourceEnvironment {

packages/aws-cdk-lib/core/test/private/detached-construct.test.ts

@@ -1,3 +1,4 @@
+import { Construct } from 'constructs';
 import { UnscopedValidationError } from '../../lib/errors';
 import { DetachedConstruct } from '../../lib/private/detached-construct';
 
@@ -21,4 +22,10 @@ describe('DetachedConstruct', () => {
     expect(() => construct.env).toThrow(UnscopedValidationError);
     expect(() => construct.env).toThrow('test error message');
   });
+
+  test('returns false for Construct.isConstruct', () => {
+    const construct = new TestDetachedConstruct('test error message');
+
+    expect(Construct.isConstruct(construct)).toBe(false);
+  });
 });