Strip restricted and incomplete handles from the "Mentions" tab on Maniphest tasks

Summary:
Ref T8345. See T8345#201048 for discussion.

This rule (don't show mentions of or from restricted objects) is more consistent with how we render mentions in the timeline and I think generally a better behavior.

Test Plan:
  - Mentioned a task on a public task and a private task.
  - Privileged user (foreground) sees both.
  - Public user (background) sees only the public mention.

{F1929485}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T8345

Differential Revision: https://secure.phabricator.com/D16900

src/applications/maniphest/controller/ManiphestTaskDetailController.php

@@ -510,15 +510,23 @@ final class ManiphestTaskDetailController extends ManiphestController {
     }
 
     $viewer = $this->getViewer();
+    $in_handles = $viewer->loadHandles($in_phids);
+    $out_handles = $viewer->loadHandles($out_phids);
+
+    $in_handles = $this->getCompleteHandles($in_handles);
+    $out_handles = $this->getCompleteHandles($out_handles);
+
+    if (!count($in_handles) && !count($out_handles)) {
+      return null;
+    }
+
     $view = new PHUIPropertyListView();
 
-    if ($in_phids) {
-      $in_handles = $viewer->loadHandles($in_phids);
+    if (count($in_handles)) {
       $view->addProperty(pht('Mentioned In'), $in_handles->renderList());
     }
 
-    if ($out_phids) {
-      $out_handles = $viewer->loadHandles($out_phids);
+    if (count($out_handles)) {
       $view->addProperty(pht('Mentioned Here'), $out_handles->renderList());
     }
 
@@ -528,4 +536,18 @@ final class ManiphestTaskDetailController extends ManiphestController {
       ->appendChild($view);
   }
 
+  private function getCompleteHandles(PhabricatorHandleList $handles) {
+    $phids = array();
+
+    foreach ($handles as $phid => $handle) {
+      if (!$handle->isComplete()) {
+        continue;
+      }
+      $phids[] = $phid;
+    }
+
+    return $handles->newSublist($phids);
+  }
+
+
 }

src/applications/phid/handle/pool/PhabricatorHandleList.php

@@ -74,6 +74,24 @@ final class PhabricatorHandleList
   }
 
 
+  /**
+   * Create a new list with a subset of the PHIDs in this list.
+   */
+  public function newSublist(array $phids) {
+    foreach ($phids as $phid) {
+      if (!isset($this[$phid])) {
+        throw new Exception(
+          pht(
+            'Trying to create a new sublist of an existsing handle list, '.
+            'but PHID "%s" does not appear in the parent list.',
+            $phid));
+      }
+    }
+
+    return $this->handlePool->newHandleList($phids);
+  }
+
+
 /* -(  Rendering  )---------------------------------------------------------- */