Pipeline util tests, clean & fix

no issue

- added comments to pipeline util, inc where it came from
- added tests for pipeline util
- tests uncovered a bug with promises for args, which has been fixed

core/server/utils/pipeline.js

@@ -1,9 +1,17 @@
+/**
+ * # Pipeline Utility
+ *
+ * Based on pipeline.js from when.js:
+ * https://github.com/cujojs/when/blob/3.7.4/pipeline.js
+ */
 var Promise = require('bluebird');
 
 function pipeline(tasks /* initial arguments */) {
     var args = Array.prototype.slice.call(arguments, 1),
 
         runTask = function (task, args) {
+            // Self-optimizing function to run first task with multiple
+            // args using apply, but subsequent tasks via direct invocation
             runTask = function (task, arg) {
                 return task(arg);
             };
@@ -11,11 +19,13 @@ function pipeline(tasks /* initial arguments */) {
             return task.apply(null, args);
         };
 
-    return Promise.all(tasks).reduce(function (arg, task) {
-        return Promise.resolve(runTask(task, arg)).then(function (result) {
-            return result;
-        });
-    }, args);
+    // Resolve any promises for the arguments passed in first
+    return Promise.all(args).then(function (args) {
+        // Iterate through the tasks passing args from one into the next
+        return Promise.reduce(tasks, function (arg, task) {
+            return runTask(task, arg);
+        }, args);
+    });
 }
 
 module.exports = pipeline;

core/test/unit/utils_pipeline_spec.js

@@ -0,0 +1,129 @@
+/*globals describe, afterEach, it*/
+/*jshint expr:true*/
+var should  = require('should'),
+    sinon   = require('sinon'),
+    Promise = require('bluebird'),
+
+// Stuff we are testing
+    pipeline = require('../../server/utils/pipeline'),
+
+    sandbox = sinon.sandbox.create();
+
+// To stop jshint complaining
+should.equal(true, true);
+
+// These tests are based on the tests in https://github.com/cujojs/when/blob/3.7.4/test/pipeline-test.js
+function createTask(y) {
+    return function (x) {
+        return x + y;
+    };
+}
+
+describe('Pipeline', function () {
+    afterEach(function () {
+        sandbox.restore();
+    });
+
+    it('should execute tasks in order', function (done) {
+        return pipeline([createTask('b'), createTask('c'), createTask('d')], 'a').then(
+            function (result) {
+                result.should.eql('abcd');
+                done();
+            }
+        );
+    });
+
+    it('should resolve to initial args when no tasks supplied', function (done) {
+        return pipeline([], 'a', 'b').then(
+            function (result) {
+                result.should.eql(['a', 'b']);
+                done();
+            }
+        );
+    });
+
+    it('should resolve to empty array when no tasks and no args supplied', function (done) {
+        return pipeline([]).then(
+            function (result) {
+                result.should.eql([]);
+                done();
+            }
+        );
+    });
+
+    it('should pass args to initial task', function (done) {
+        var expected = [1, 2, 3],
+            tasks = [sandbox.spy()];
+
+        return pipeline(tasks, 1, 2, 3).then(
+            function () {
+                tasks[0].calledOnce.should.be.true;
+                tasks[0].firstCall.args.should.eql(expected);
+
+                done();
+            }
+        );
+    });
+
+    it('should allow initial args to be promises', function (done) {
+        var expected = [1, 2, 3],
+            tasks = [sandbox.spy()],
+            Resolver = Promise.resolve;
+
+        return pipeline(tasks, new Resolver(1), new Resolver(2), new Resolver(3)).then(
+            function () {
+                tasks[0].calledOnce.should.be.true;
+                tasks[0].firstCall.args.should.eql(expected);
+
+                done();
+            }
+        );
+    });
+
+    it('should allow tasks to be promises', function (done) {
+        var expected = [1, 2, 3],
+            tasks = [
+                sandbox.stub().returns(new Promise.resolve(4)),
+                sandbox.stub().returns(new Promise.resolve(5)),
+                sandbox.stub().returns(new Promise.resolve(6))
+            ];
+
+        return pipeline(tasks, 1, 2, 3).then(
+            function (result) {
+                result.should.eql(6);
+                tasks[0].calledOnce.should.be.true;
+                tasks[0].firstCall.args.should.eql(expected);
+                tasks[1].calledOnce.should.be.true;
+                tasks[1].firstCall.calledWith(4).should.be.true;
+                tasks[2].calledOnce.should.be.true;
+                tasks[2].firstCall.calledWith(5).should.be.true;
+
+                done();
+            }
+        );
+    });
+
+    it('should allow tasks and args to be promises', function (done) {
+        var expected = [1, 2, 3],
+            tasks = [
+                sandbox.stub().returns(new Promise.resolve(4)),
+                sandbox.stub().returns(new Promise.resolve(5)),
+                sandbox.stub().returns(new Promise.resolve(6))
+            ],
+            Resolver = Promise.resolve;
+
+        return pipeline(tasks, new Resolver(1), new Resolver(2), new Resolver(3)).then(
+            function (result) {
+                result.should.eql(6);
+                tasks[0].calledOnce.should.be.true;
+                tasks[0].firstCall.args.should.eql(expected);
+                tasks[1].calledOnce.should.be.true;
+                tasks[1].firstCall.calledWith(4).should.be.true;
+                tasks[2].calledOnce.should.be.true;
+                tasks[2].firstCall.calledWith(5).should.be.true;
+
+                done();
+            }
+        );
+    });
+});