Allow detectPackage with a function (#811)

packages/util/src/detectPackage.spec.ts

@@ -7,7 +7,10 @@ describe('assertSingletonPackage', (): void => {
   const PKG = '@polkadot/util';
   const VER1 = '9.8.0-beta.45';
   const VER2 = '9.7.1';
+  const VER3 = '9.6.1';
   const PATH = '/Users/jaco/Projects/polkadot-js/api/node_modules/@polkadot/util';
+  const RES2 = `Multiple instances of @polkadot/util detected, ensure that there is only one package in your dependency tree.\n\t${VER1}\t${PATH}/01\n\t${VER2}        \t${PATH}/02`;
+  const RES3 = `${RES2}\n\t${VER3}        \t${PATH}/03`;
 
   it('should not log the first time', (): void => {
     const spy = jest.spyOn(console, 'warn');
@@ -21,7 +24,15 @@ describe('assertSingletonPackage', (): void => {
     const spy = jest.spyOn(console, 'warn');
 
     detectPackage({ name: PKG, version: VER2 }, `${PATH}/02`);
-    expect(spy).toHaveBeenCalledWith(`Multiple instances of @polkadot/util detected, ensure that there is only one package in your dependency tree.\n\t${VER1}\t${PATH}/01\n\t${VER2}        \t${PATH}/02`);
+    expect(spy).toHaveBeenCalledWith(RES2);
+    spy.mockRestore();
+  });
+
+  it('should allow for function use', (): void => {
+    const spy = jest.spyOn(console, 'warn');
+
+    detectPackage({ name: PKG, version: VER3 }, () => `${PATH}/03`);
+    expect(spy).toHaveBeenCalledWith(RES3);
     spy.mockRestore();
   });
 });

packages/util/src/detectPackage.ts

@@ -1,6 +1,7 @@
 // Copyright 2017-2020 @polkadot/util authors & contributors
 // SPDX-License-Identifier: Apache-2.0
 
+import { isFunction } from './is/function';
 import { isString } from './is/string';
 import { assert } from './assert';
 
@@ -23,6 +24,7 @@ interface PjsChecks extends This {
 
 type PjsGlobal = NodeJS.Global & PjsChecks;
 type PjsWindow = Window & PjsChecks;
+type FnString = () => string | undefined;
 
 function expandPath (path?: string): string {
   return (!path || path.length < 5) ? '<unknown>' : path;
@@ -42,11 +44,24 @@ function flattenVersions (_all: (VersionPath | string)[]): string {
     .join('\n');
 }
 
+/** @internal */
+function getPath (pathOrFn?: FnString | string | false): false | string | undefined {
+  if (isFunction(pathOrFn)) {
+    try {
+      return pathOrFn();
+    } catch (error) {
+      return undefined;
+    }
+  }
+
+  return pathOrFn;
+}
+
 /**
  * @name detectPackage
  * @summary Checks that a specific package is only imported once
  */
-export function detectPackage ({ name, version }: PackageJson, path?: string | false): void {
+export function detectPackage ({ name, version }: PackageJson, pathOrFn?: FnString | string | false): void {
   const _global = typeof window !== 'undefined'
     ? window as PjsWindow
     : global as PjsGlobal;
@@ -57,6 +72,8 @@ export function detectPackage ({ name, version }: PackageJson, path?: string | f
 
   assert(name.startsWith('@polkadot'), `Invalid package descriptor ${name}`);
 
+  const path = getPath(pathOrFn);
+
   _global.__polkadotjs[name] = [...(_global.__polkadotjs[name] || []), { path: path || '', version }];
 
   if (_global.__polkadotjs[name].length !== 1) {