bug: Setting [mode]=" 'not ios or md' " causes './undefined.entry.js' Error

Bug Report

Ionic version:

[x] 5.0.0-beta.1

Current behavior:

Set an invalid value for any [mode] flag. The following error occurs.

core-9d3f3c18.js:63 Error: Cannot find module './undefined.entry.js'
    at .*\.entry\.js$ include: \.entry\.js$ exclude: \.system\.entry\.js$ namespace object:385
    at ZoneDelegate.invoke (zone-evergreen.js:359)
    at Zone.run (zone-evergreen.js:124)
    at zone-evergreen.js:855
    at ZoneDelegate.invokeTask (zone-evergreen.js:391)
    at Zone.runTask (zone-evergreen.js:168)
    at drainMicroTaskQueue (zone-evergreen.js:559)
consoleError @ core-9d3f3c18.js:63
invoke @ zone-evergreen.js:359
run @ zone-evergreen.js:124
(anonymous) @ zone-evergreen.js:855
invokeTask @ zone-evergreen.js:391
runTask @ zone-evergreen.js:168
drainMicroTaskQueue @ zone-evergreen.js:559
Promise.then (async)
scheduleMicroTask @ zone-evergreen.js:542
scheduleTask @ zone-evergreen.js:381
onScheduleTask @ zone-evergreen.js:272
scheduleTask @ zone-evergreen.js:372
scheduleTask @ zone-evergreen.js:211
scheduleMicroTask @ zone-evergreen.js:231
scheduleResolveOrReject @ zone-evergreen.js:845
resolvePromise @ zone-evergreen.js:791
(anonymous) @ zone-evergreen.js:707
webpackJsonpCallback @ bootstrap:25
(anonymous) @ tab1-tab1-module.js:13


zone-evergreen.js:651 Unhandled Promise rejection: Cannot read property 'isProxied' of undefined ; Zone: <root> ; Task: Promise.then ; Value: TypeError: Cannot read property 'isProxied' of undefined
    at initializeComponent (core-9d3f3c18.js:1737) TypeError: Cannot read property 'isProxied' of undefined
    at initializeComponent (http://localhost:8101/vendor.js:105947:24)

Expected behavior:

An error should be displayed that tells the user where to find the issue in question. Right now it is virtually impossible to track this down unless you know what you are doing. I only found it by deleting code until the error went away, then adding it back, and so on, until I was able to pinpoint the problem.

Steps to reproduce:

1. ionic start myApp tabs
2. Edit tab1.page.html and add mode=foo to any ion-item component.
3. Reload page… kapow.

Related code:

      <ion-item href="https://ionicframework.com/docs/" mode=foo>
        <ion-icon slot="start" color="medium" name="book"></ion-icon>
        <ion-label>Ionic Documentation</ion-label>
      </ion-item>

Other information:

Ionic info:

Ionic:

   Ionic CLI                     : 5.4.10 (/usr/local/lib/node_modules/ionic)
   Ionic Framework               : @ionic/angular 5.0.0-beta.1
   @angular-devkit/build-angular : 0.801.3
   @angular-devkit/schematics    : 8.1.3
   @angular/cli                  : 8.1.3
   @ionic/angular-toolkit        : 2.1.1

Utility:

   cordova-res : not installed
   native-run  : not installed

System:

   NodeJS : v12.13.0 (/usr/local/lib/node_modules/node/bin/node)
   npm    : 6.13.1
   OS     : macOS Catalina

[liamdebeasi]

Thanks for the issue. This has been resolved via https://github.com/ionic-team/ionic/pull/20828 and will be available in an upcoming release of Ionic Framework.

[lincolnthree]

Yep. These are the little typo/random issues that add up to cause developer fatigue.

Submitted both as a reference to other folks who happen upon the same issue, and also so it can hopefully be addressed to avoid the confusion/stack/error searching entirely for future users. Thanks for taking a look / considering.