feat(errors): propogate thrown errors by configuring error handler (#154)

* Propogate thrown errors by configuring error handler and attaching in mount function resolves #147

* set errorHandler to be a default export and set Vue.config.errorHandler = errorHandler in mount

* Add test for create-local-vue error handler being defined and configure that in create local vue

Author: Austio

src/create-local-vue.js

@@ -2,6 +2,7 @@
 
 import Vue from 'vue'
 import cloneDeep from 'lodash/cloneDeep'
+import errorHandler from './lib/error-handler'
 
 function createLocalVue (): Component {
   const instance = Vue.extend()
@@ -19,6 +20,8 @@ function createLocalVue (): Component {
   // config is not enumerable
   instance.config = cloneDeep(Vue.config)
 
+  instance.config.errorHandler = errorHandler
+
   // option merge strategies need to be exposed by reference
   // so that merge strats registered by plguins can work properly
   instance.config.optionMergeStrategies = Vue.config.optionMergeStrategies

src/lib/error-handler.js

@@ -0,0 +1,19 @@
+function errorMessage (msg, info) {
+  if (info) {
+    return `${msg} : additional info ${info}`
+  }
+
+  return msg
+}
+
+export default function errorHandler (err, _vm, info) {
+  if ((typeof err === 'object') && err.message) {
+    if (info) {
+      err.message = errorMessage(err.message, info)
+    }
+
+    throw err
+  }
+
+  throw new Error(errorMessage(err, info))
+}

src/mount.js

@@ -7,8 +7,10 @@ import createInstance from './lib/create-instance'
 import cloneDeep from 'lodash/cloneDeep'
 import createElement from './lib/create-element'
 import './lib/matches-polyfill'
+import errorHandler from './lib/error-handler'
 
 Vue.config.productionTip = false
+Vue.config.errorHandler = errorHandler
 
 export default function mount (component: Component, options: Options = {}): VueWrapper {
   const componentToMount = options.clone === false ? component : cloneDeep(component.extend ? component.options : component)

test/unit/specs/create-local-vue.spec.js

@@ -112,4 +112,10 @@ describe('createLocalVue', () => {
     const localVue = createLocalVue()
     localVue.use(Vuetify)
   })
+
+  it('has an errorHandler', () => {
+    const localVue = createLocalVue()
+
+    expect(localVue.config.errorHandler).to.be.an('function')
+  })
 })

test/unit/specs/lib/error-handler.spec.js

@@ -0,0 +1,31 @@
+import errorHandler from '../../../../src/lib/error-handler'
+
+describe('errorHandler', () => {
+  const errorString = 'errorString'
+  const info = 'additional info provided by vue'
+  const errorObject = new Error(errorString)
+
+  it('when error object: rethrows error', () => {
+    expect(() => errorHandler(errorObject)).to.throw().with.property('message', errorString)
+  })
+
+  it('when error object: rethrown error contains vue info when provided', () => {
+    expect(() => errorHandler(errorObject, {}, info)).to.throw().that.satisfies(function (err) {
+      const errorMessage = err.message
+
+      return errorMessage.includes(errorString) && errorMessage.includes(info)
+    })
+  })
+
+  it('when error string: throws error with string', () => {
+    expect(() => errorHandler(errorString)).to.throw().with.property('message', errorString)
+  })
+
+  it('throws error with string and appends info when provided', () => {
+    expect(() => errorHandler(errorString, {}, info)).to.throw().that.satisfies(function (err) {
+      const errorMessage = err.message
+
+      return errorMessage.includes(errorString) && errorMessage.includes(info)
+    })
+  })
+})

test/unit/specs/mount.spec.js

@@ -85,4 +85,13 @@ describe('mount', () => {
     expect(wrapper.vm).to.be.an('object')
     expect(wrapper.html()).to.equal(`<div>foo</div>`)
   })
+
+  it('throws an error when the component fails to mount', () => {
+    expect(() => mount({
+      template: '<div></div>',
+      mounted: function () {
+        throw (new Error('Error'))
+      }
+    })).to.throw()
+  })
 })

test/unit/specs/shallow.spec.js

@@ -74,4 +74,13 @@ describe('shallow', () => {
     shallow(ComponentWithNestedChildren)
     expect(info.called).to.equal(false)
   })
+
+  it('throws an error when the component fails to mount', () => {
+    expect(() => shallow({
+      template: '<div></div>',
+      mounted: function () {
+        throw (new Error('Error'))
+      }
+    })).to.throw()
+  })
 })