fix: Deal with absence truth-test function

References mblarsen/vue-browser-acl#8

index.js

@@ -1,7 +1,10 @@
 
 export const GlobalRule = 'GLOBAL_RULE'
 
-const isNameless = fn => typeof fn === 'function' && fn.name === ''
+const assumeGlobal = sub =>
+  typeof sub === 'boolean' ||
+  typeof sub === 'undefined' ||
+  (typeof sub === 'function' && sub.name === '')
 
 /**
  * Simple ACL library for the browser inspired by Laravel's guards and policies.
@@ -48,8 +51,8 @@ export default class Acl {
    * @returns {Acl}
    */
   rule(verbs, subject, test = true) {
-    if (isNameless(subject)) {
-      test = subject
+    if (assumeGlobal(subject)) {
+      test = typeof subject === 'undefined' ? true : subject
       subject = GlobalRule
     }
     const subjectName = this.subjectMapper(subject)

test/Acl.test.js

@@ -1,4 +1,4 @@
-import Acl from '../index.js'
+import Acl, {GlobalRule} from '../index.js'
 
 class User {}
 class Apple {}
@@ -21,6 +21,12 @@ describe('The basics', () => {
     acl.rule('purgeInactive', user => user.isAdmin)
     expect(acl.can({isAdmin: true}, 'purgeInactive')).toBe(true)
     expect(acl.can({isAdmin: false}, 'purgeInactive')).toBe(false)
+    acl.rule('contact')
+    expect(acl.can({}, 'contact')).toBe(true)
+    acl.rule('contact', false)
+    expect(acl.can({}, 'contact')).toBe(false)
+    acl.rule('pillage', false)
+    expect(acl.can({}, 'pillage')).toBe(false)
   })
 
   test('Cannot eat apples (no rule)', () => {