Ensure arguments are passed down to trigger (#381)

When we switched our `drop` implementation away from lodash, we accidentally stopped passing things like `step` and `previous` down to subsequent trigger calls. This fixes the `drop` call by ensuring `arguments` is now an array.

Fixes #371

babel.config.js

@@ -28,6 +28,7 @@ module.exports = function(api) {
           ]
         ],
         plugins: [
+          'rewire-exports',
           'transform-es2015-modules-commonjs'
         ]
       }

package.json

@@ -53,17 +53,18 @@
     "tippy.js": "^4.3.0"
   },
   "devDependencies": {
-    "@babel/core": "^7.4.4",
+    "@babel/core": "^7.4.5",
     "@babel/plugin-transform-object-assign": "^7.2.0",
-    "@babel/preset-env": "^7.4.4",
+    "@babel/preset-env": "^7.4.5",
     "autoprefixer": "^9.5.1",
     "babel-core": "^7.0.0-bridge.0",
     "babel-jest": "^24.7.1",
+    "babel-plugin-rewire-exports": "^1.1.0",
     "babel-plugin-transform-es2015-modules-commonjs": "^6.26.2",
     "chai": "^4.2.0",
     "codeclimate-test-reporter": "^0.5.1",
     "cssnano": "^4.1.10",
-    "cypress": "^3.2.0",
+    "cypress": "^3.3.1",
     "del": "^4.1.1",
     "esdoc": "^1.1.0",
     "esdoc-ecmascript-proposal-plugin": "^1.0.0",
@@ -87,7 +88,7 @@
     "rollup-plugin-commonjs": "^9.3.4",
     "rollup-plugin-css-only": "^1.0.0",
     "rollup-plugin-eslint": "^6.0.0",
-    "rollup-plugin-filesize": "^6.0.1",
+    "rollup-plugin-filesize": "^6.1.0",
     "rollup-plugin-license": "^0.8.1",
     "rollup-plugin-multi-entry": "^2.1.0",
     "rollup-plugin-node-resolve": "^5.0.0",
@@ -96,7 +97,7 @@
     "rollup-plugin-terser": "^5.0.0",
     "rollup-plugin-visualizer": "^1.1.1",
     "sinon": "^7.3.2",
-    "start-server-and-test": "^1.9.0",
+    "start-server-and-test": "^1.9.1",
     "stylelint": "^10.0.1",
     "stylelint-config-ship-shape": "^0.5.2"
   },

src/js/evented.js

@@ -36,7 +36,7 @@ export class Evented {
 
   trigger(event) {
     if (!isUndefined(this.bindings) && this.bindings[event]) {
-      const args = drop(arguments);
+      const args = drop(Array.prototype.slice.call(arguments));
 
       this.bindings[event].forEach((binding, index) => {
         const { ctx, handler, once } = binding;

test/unit/tour.spec.js

@@ -5,6 +5,7 @@ import { Step } from '../../src/js/step.js';
 import tippy from 'tippy.js';
 import { defaults as tooltipDefaults } from '../../src/js/utils/tooltip-defaults';
 import { spy } from 'sinon';
+import { drop, rewire$drop, restore } from '../../src/js/utils/general';
 
 // since importing non UMD, needs assignment
 window.Shepherd = Shepherd;
@@ -379,6 +380,14 @@ describe('Tour | Top-Level Class', function() {
     });
 
     describe('.show()', function() {
+      let dropSpy;
+
+      beforeEach(() => {
+        rewire$drop(dropSpy = spy(drop));
+      });
+
+      afterEach(restore);
+
       it('show short-circuits if next is not found', function() {
         let showFired = false;
         instance.start();
@@ -399,6 +408,15 @@ describe('Tour | Top-Level Class', function() {
         shouldShowStep = true;
         instance.next();
         expect(instance.getCurrentStep().id, 'step shown because `showOn` returns true').toBe('skipped-step');
+
+        // This spy checks that, when we call `trigger` with `show`, that we pass `arguments` down.
+        const dropArguments = dropSpy.args[2][0];
+        const dropReturnValue = dropSpy.returnValues[2][0];
+        expect(dropArguments[0]).toBe('show');
+        expect(dropArguments[1].previous).toBe(null);
+        expect(dropArguments[1].step.id).toBe('test');
+        expect(dropReturnValue.previous).toBe(null);
+        expect(dropReturnValue.step.id).toBe('test');
       });
 
       it(`sets the instance on \`Shepherd.activeTour\` if it's not already set`, function() {