Provide task closed date via Conduit API, data export pipeline, and in list UI

Summary:
Depends on D19037. Ref T4434. Adds closed date to `maniphest.search` and "Export Data".

When a task has been closed, show the closed date with a checkmark in the UI instead of the modified date.

Test Plan:
  - Exported data to CSV, saw close information.
  - Saw close information in `/maniphest/`.
  - Queried for close information via `maniphest.search`.

Maniphest Tasks: T4434

Differential Revision: https://secure.phabricator.com/D19038

src/applications/maniphest/query/ManiphestTaskSearchEngine.php

@@ -456,6 +456,15 @@ final class ManiphestTaskSearchEngine
       id(new PhabricatorStringExportField())
         ->setKey('statusName')
         ->setLabel(pht('Status Name')),
+      id(new PhabricatorEpochExportField())
+        ->setKey('dateClosed')
+        ->setLabel(pht('Date Closed')),
+      id(new PhabricatorPHIDExportField())
+        ->setKey('closerPHID')
+        ->setLabel(pht('Closer PHID')),
+      id(new PhabricatorStringExportField())
+        ->setKey('closer')
+        ->setLabel(pht('Closer')),
       id(new PhabricatorStringExportField())
         ->setKey('priority')
         ->setLabel(pht('Priority')),
@@ -492,6 +501,7 @@ final class ManiphestTaskSearchEngine
     foreach ($tasks as $task) {
       $phids[] = $task->getAuthorPHID();
       $phids[] = $task->getOwnerPHID();
+      $phids[] = $task->getCloserPHID();
     }
     $handles = $viewer->loadHandles($phids);
 
@@ -512,6 +522,13 @@ final class ManiphestTaskSearchEngine
         $owner_name = null;
       }
 
+      $closer_phid = $task->getCloserPHID();
+      if ($closer_phid) {
+        $closer_name = $handles[$closer_phid]->getName();
+      } else {
+        $closer_name = null;
+      }
+
       $status_value = $task->getStatus();
       $status_name = ManiphestTaskStatus::getTaskStatusName($status_value);
 
@@ -534,6 +551,9 @@ final class ManiphestTaskSearchEngine
         'title' => $task->getTitle(),
         'uri' => PhabricatorEnv::getProductionURI($task->getURI()),
         'description' => $task->getDescription(),
+        'dateClosed' => $task->getClosedEpoch(),
+        'closerPHID' => $closer_phid,
+        'closer' => $closer_name,
       );
     }
 

src/applications/maniphest/storage/ManiphestTask.php

@@ -513,6 +513,16 @@ final class ManiphestTask extends ManiphestDAO
         ->setKey('subtype')
         ->setType('string')
         ->setDescription(pht('Subtype of the task.')),
+      id(new PhabricatorConduitSearchFieldSpecification())
+        ->setKey('closerPHID')
+        ->setType('phid?')
+        ->setDescription(
+          pht('User who closed the task, if the task is closed.')),
+      id(new PhabricatorConduitSearchFieldSpecification())
+        ->setKey('dateClosed')
+        ->setType('int?')
+        ->setDescription(
+          pht('Epoch timestamp when the task was closed.')),
     );
   }
 
@@ -532,6 +542,11 @@ final class ManiphestTask extends ManiphestDAO
       'color' => ManiphestTaskPriority::getTaskPriorityColor($priority_value),
     );
 
+    $closed_epoch = $this->getClosedEpoch();
+    if ($closed_epoch !== null) {
+      $closed_epoch = (int)$closed_epoch;
+    }
+
     return array(
       'name' => $this->getTitle(),
       'description' => array(
@@ -543,6 +558,8 @@ final class ManiphestTask extends ManiphestDAO
       'priority' => $priority_info,
       'points' => $this->getPoints(),
       'subtype' => $this->getSubtype(),
+      'closerPHID' => $this->getCloserPHID(),
+      'dateClosed' => $closed_epoch,
     );
   }
 

src/applications/maniphest/view/ManiphestTaskListView.php

@@ -86,9 +86,24 @@ final class ManiphestTaskListView extends ManiphestView {
 
       $item->setStatusIcon($icon.' '.$color, $tooltip);
 
-      $item->addIcon(
-        'none',
-        phabricator_datetime($task->getDateModified(), $this->getUser()));
+      if ($task->isClosed()) {
+        $closed_epoch = $task->getClosedEpoch();
+
+        // We don't expect a task to be closed without a closed epoch, but
+        // recover if we find one. This can happen with older objects or with
+        // lipsum test data.
+        if (!$closed_epoch) {
+          $closed_epoch = $task->getDateModified();
+        }
+
+        $item->addIcon(
+          'fa-check-square-o grey',
+          phabricator_datetime($closed_epoch, $this->getUser()));
+      } else {
+        $item->addIcon(
+          'none',
+          phabricator_datetime($task->getDateModified(), $this->getUser()));
+      }
 
       if ($this->showSubpriorityControls) {
         $item->setGrippable(true);