Consistent return value from target-manager.getTargets

It should always return a Promise.

Fixes #420

lib/target-manager.js

@@ -159,8 +159,9 @@ class TargetManager extends EventEmitter {
     const activeTarget = this.getActiveTarget(path);
     activeTarget && this.targetsView.setActiveTarget(activeTarget.name);
 
-    const targetNames = this.getTargets(path).map(t => t.name);
-    this.targetsView && this.targetsView.setItems(targetNames);
+    this.getTargets(path)
+      .then(targets => targets.map(t => t.name))
+      .then(targetNames => this.targetsView && this.targetsView.setItems(targetNames));
   }
 
   selectActiveTarget() {
@@ -198,13 +199,13 @@ class TargetManager extends EventEmitter {
   getTargets(path) {
     const pathTarget = this.pathTargets.find(pt => pt.path === path);
     if (!pathTarget) {
-      return [];
+      return Promise.resolve([]);
     }
 
     if (pathTarget.targets.length === 0) {
       return this.refreshTargets([ pathTarget.path ]).then(() => pathTarget.targets);
     }
-    return pathTarget.targets;
+    return Promise.resolve(pathTarget.targets);
   }
 
   getActiveTarget(path) {