assertSingleton warns, not throws (#455)

packages/util/src/assertSingletonPackage.spec.ts

@@ -7,15 +7,19 @@ import { assertSingletonPackage } from '.';
 describe('assertSingletonPackage', (): void => {
   const NAME = 'assertSingletonPackage';
 
-  it('should not throw the first time', (): void => {
-    expect(
-      (): void => assertSingletonPackage(NAME)
-    ).not.toThrow();
+  it('should not log the first time', (): void => {
+    const spy = jest.spyOn(console, 'warn');
+
+    assertSingletonPackage(NAME);
+    expect(spy).not.toHaveBeenCalled();
+    spy.mockRestore();
   });
 
-  it('should throw the second time', (): void => {
-    expect(
-      (): void => assertSingletonPackage(NAME)
-    ).toThrow(/Multiple versions of assertSingletonPackage detected/);
+  it('should log the second time', (): void => {
+    const spy = jest.spyOn(console, 'warn');
+
+    assertSingletonPackage(NAME);
+    expect(spy).toHaveBeenCalledWith('Multiple versions of assertSingletonPackage detected, ensure that there is only one version in your dependency tree');
+    spy.mockRestore();
   });
 });

packages/util/src/assertSingletonPackage.ts

@@ -3,7 +3,6 @@
 // of the Apache-2.0 license. See the LICENSE file for details.
 
 import isUndefined from './is/undefined';
-import assert from './assert';
 
 interface PjsChecks {
   __polkadotjs: Record<string, boolean>;
@@ -25,7 +24,9 @@ export default function assertSingletonPackage (name: string): void {
     _global.__polkadotjs = {};
   }
 
-  assert(isUndefined(_global.__polkadotjs[name]), `Multiple versions of ${name} detected, ensure that there is only version one in your dependency tree`);
+  if (!isUndefined(_global.__polkadotjs[name])) {
+    console.warn(`Multiple versions of ${name} detected, ensure that there is only one version in your dependency tree`);
+  }
 
   _global.__polkadotjs[name] = true;
 }