title: Visual Studio warning: Undeclared mixin in .less file
body: <p>I am using VS 2017. I have bought a CSS template, which is structured as below (I believe it is quite typical):</p>
  
  <p>All the mixins are declared in a file called mixins.less</p>
  
  <p><strong>mixins.less</strong></p>
  
  <pre><code>.transition-delay(@delay: 0) {
    -moz-transition-delay: @delay;
    -webkit-transition-delay: @delay;
    -o-transition-delay: @delay;
    transition-delay: @delay;
  }
  // more mixins
  </code></pre>
  
  <p>and then I have several style files which use these mixins (e.g. header.less &amp; product.less)</p>
  
  <p><strong>header.less</strong></p>
  
  <pre><code>h2 {
    .transition-delay(1s);
  }
  // more css
  </code></pre>
  
  <p><strong>product.less</strong></p>
  
  <pre><code>div.someClass {
    .transition-delay(1s);
  }
  // more css
  </code></pre>
  
  <p>Finally I have style.less, where everything comes together:</p>
  
  <p><strong>style.less</strong></p>
  
  <pre><code>@import "mixins.less";
  @import "header.less";
  @import "product.less";
  </code></pre>
  
  <p>when I compile style.less, everything gets complied into style.css and style.css is added to my web project.</p>
  
  <p>This works fine, the only problem is when compiling the project, Visual Studio gives a lot of warnings:</p>
  
  <blockquote>
    <p>Undeclared mixin</p>
  </blockquote>
  
  <p>This is because I am using <code>.transition-delay</code> in header.less. VS warning is valid, as I have not declared the mixin in header.less... but then I don't need to compile header.less, the only file that I need to compile is style.less.</p>
  
  <p>Is there anyway to tell VS to ignore header.less and product.less and not give me any mixin warnings?</p>