fix: urls.primaryName functionality regression (via #5097)

* add tests

* compute index before triggering URL load

* bonus: improve urls topbar label

src/plugins/topbar/topbar.jsx

@@ -74,7 +74,7 @@ export default class Topbar extends React.Component {
     const urls = configs.urls || []
 
     if(urls && urls.length) {
-      this.loadSpec(urls[this.state.selectedIndex].url)
+      var targetIndex = this.state.selectedIndex
       let primaryName = configs["urls.primaryName"]
       if(primaryName)
       {
@@ -82,9 +82,12 @@ export default class Topbar extends React.Component {
           if(spec.name === primaryName)
             {
               this.setState({selectedIndex: i})
+              targetIndex = i
             }
         })
       }
+
+      this.loadSpec(urls[targetIndex].url)
     }
   }
 
@@ -116,7 +119,7 @@ export default class Topbar extends React.Component {
       })
 
       control.push(
-        <label className="select-label" htmlFor="select"><span>Select a spec</span>
+        <label className="select-label" htmlFor="select"><span>Select a definition</span>
           <select id="select" disabled={isLoading} onChange={ this.onUrlSelect } value={urls[this.state.selectedIndex].url}>
             {rows}
           </select>

src/style/_topbar.scss

@@ -54,6 +54,7 @@
             width: 100%;
             max-width: 600px;
             margin: 0;
+            color: #f0f0f0;
             span
             {
                 font-size: 16px;