Merge pull request #2305 from MetaMask/nodeify

nodeify - allow callback to be optional

app/scripts/lib/nodeify.js

@@ -1,10 +1,18 @@
 const promiseToCallback = require('promise-to-callback')
+const noop = function(){}
 
 module.exports = function nodeify (fn, context) {
   return function(){
     const args = [].slice.call(arguments)
-    const callback = args.pop()
-    if (typeof callback !== 'function') throw new Error('callback is not a function')
+    const lastArg = args[args.length - 1]
+    const lastArgIsCallback = typeof lastArg === 'function'
+    let callback
+    if (lastArgIsCallback) {
+      callback = lastArg
+      args.pop()
+    } else {
+      callback = noop
+    }
     promiseToCallback(fn.apply(context, args))(callback)
   }
 }

test/unit/nodeify-test.js

@@ -18,14 +18,13 @@ describe('nodeify', function () {
     })
   })
 
-  it('should throw if the last argument is not a function', function (done) {
+  it('should allow the last argument to not be a function', function (done) {
     const nodified = nodeify(obj.promiseFunc, obj)
     try {
       nodified('baz')
-      done(new Error('should have thrown if the last argument is not a function'))
-    } catch (err) {
-      assert.equal(err.message, 'callback is not a function')
       done()
+    } catch (err) {
+      done(new Error('should not have thrown if the last argument is not a function'))
     }
   })
 })