Allow fn passed to Async.fromNode to be partially applied

Author: JamieDixon

src/Async/Async.spec.js

@@ -225,6 +225,21 @@ test('Async fromNode resolution', t => {
   Async.fromNode(resCPS)(val).fork(rej(val), res(val))
 })
 
+test('Async fromNode partially applied', t => {
+  t.plan(2)
+
+  const val = 'super fun'
+
+  const rejCPS = (x, y, cf) => cf(x, y)
+  const resCPS = (x, y, cf) => cf(null, x, y)
+
+  const rej = y => x => t.equal(x, y, 'rejects an erred CPS')
+  const res = y => x => t.equal(x, y, 'resolves a good CPS')
+
+  Async.fromNode(rejCPS)(val)(val).fork(rej(val), res(val))
+  Async.fromNode(resCPS)(val)(val).fork(rej(val), res(val))
+})
+
 test('Async all', t => {
   const all = bindFunc(Async.all)
 

src/Async/index.js

@@ -48,14 +48,22 @@ function fromNode(fn, ctx) {
     throw new TypeError('Async.fromNode: CPS function required')
   }
 
-  return (...args) =>
-    Async((reject, resolve) => {
+  const _fn = curry(fn)
+
+  return (...args) => {
+
+    if (args.length < _fn.length - 1) {
+      return fromNode(_fn(...args), ctx)
+    }
+
+    return Async((reject, resolve) => {
       fn.apply(ctx,
         args.concat(
           (err, data) => err ? reject(err) : resolve(data)
         )
       )
     })
+  }
 }
 
 function fromPromise(fn) {