ngClass and conditions #17274

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Current behavior

When using ngClass Directive with 2 conditions, it seems that similar class used in both are removed when the first condition is true.

Consider the following code to display standard Bootstrap alert if the server is online or offline.

<div [ngClass]="{'alert alert-danger': serverStatus!='online','alert alert-success': serverStatus==='online'}">

Expected behavior

Expected result is

<div class="alert alert-danger">Server is not online</div>
or
<div class="alert alert-success">Server is online</div>

Result is

<div class="alert-danger">Server is not online</div> -- Missing class 'alert'
or
<div class="alert alert-success">Server is online</div> -- OK

Minimal reproduction of the problem with instructions

Pushing the test as far as i can, every similar class existing on both condition are "removed" when the first condition is true.

Just for the sake of demonstration.

<div [ngClass]="{'alert alert-success': serverStatus!='online','alert alert-success': serverStatus==='online'}">

Result is

<div >Server is not online</div> -- no class at all
or
<div class="alert alert-success>Server is online</div> -- OK

Please tell us about your environment:
MacOSX

• Angular version: 4.0.X

• Browser: [all]

• Language: [TypeScript ]

Thank you for your review.

Arnaud