title: You should not have pug tags with multiple attributes
body: <h1>Pug mixin with computed CSS class name</h1>
  
  <p>My pug mixin <code>tweet</code> normally just generates this HTML:</p>
  
  <pre><code>&lt;div class='col-md-3'&gt;&lt;/div&gt;
  </code></pre>
  
  <p>I pass <code>tweet</code> the parameter <code>index</code>, which is a zero-based positive number. When <code>index</code> equals <code>tweetData.index</code> (defined elsewhere) I want the generated <code>div</code> to glow, like this:</p>
  
  <pre><code>&lt;div class='blueGlow col-md-3'&gt;&lt;/div&gt;
  </code></pre>
  
  <p>This is my attempt:</p>
  
  <pre><code>mixin tweet(index)
      div.collapse(class= tweetData.index === index ? "blueGlow" : undefined).col-md-3(data-index=index)
  </code></pre>
  
  <p>The error message is: <code>You should not have pug tags with multiple attributes.</code></p>