When a task graph has too much stuff, only show adjacent nodes (direct parents/children)

Summary:
Ref T4788. This gives us a new level of graceful degradation, so now we show:

  - Zero through 100 connected tasks: whole graph.
  - More than 100 connnected tasks, but fewer than 100 direct parents/subtasks: just parents and subtasks, with "..." to hint that the graph is cut off.
  - More than 100 parents and children: just the "sorry, too much stuff" error message.

Test Plan: {F1740882}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T4788

Differential Revision: https://secure.phabricator.com/D16344

src/applications/maniphest/controller/ManiphestTaskDetailController.php

@@ -94,27 +94,40 @@ final class ManiphestTaskDetailController extends ManiphestController {
       ->setLimit($graph_limit)
       ->loadGraph();
     if (!$task_graph->isEmpty()) {
-      if ($task_graph->isOverLimit()) {
+      $parent_type = ManiphestTaskDependedOnByTaskEdgeType::EDGECONST;
+      $subtask_type = ManiphestTaskDependsOnTaskEdgeType::EDGECONST;
+      $parent_map = $task_graph->getEdges($parent_type);
+      $subtask_map = $task_graph->getEdges($subtask_type);
+      $parent_list = idx($parent_map, $task->getPHID(), array());
+      $subtask_list = idx($subtask_map, $task->getPHID(), array());
+      $has_parents = (bool)$parent_list;
+      $has_subtasks = (bool)$subtask_list;
+
+      $search_text = pht('Search...');
+
+      // First, get a count of direct parent tasks and subtasks. If there
+      // are too many of these, we just don't draw anything. You can use
+      // the search button to browse tasks with the search UI instead.
+      $direct_count = count($parent_list) + count($subtask_list);
+
+      if ($direct_count > $graph_limit) {
         $message = pht(
-          'Task graph too large to display (this task is connected to '.
-          'more than %s other tasks).',
-          $graph_limit);
+          'Task graph too large to display (this task is directly connected '.
+          'to more than %s other tasks). Use %s to explore connected tasks.',
+          $graph_limit,
+          phutil_tag('strong', array(), $search_text));
         $message = phutil_tag('em', array(), $message);
         $graph_table = id(new PHUIPropertyListView())
           ->addTextContent($message);
       } else {
+        // If there aren't too many direct tasks, but there are too many total
+        // tasks, we'll only render directly connected tasks.
+        if ($task_graph->isOverLimit()) {
+          $task_graph->setRenderOnlyAdjacentNodes(true);
+        }
         $graph_table = $task_graph->newGraphTable();
       }
 
-      $parent_type = ManiphestTaskDependedOnByTaskEdgeType::EDGECONST;
-      $subtask_type = ManiphestTaskDependsOnTaskEdgeType::EDGECONST;
-
-      $parent_map = $task_graph->getEdges($parent_type);
-      $subtask_map = $task_graph->getEdges($subtask_type);
-
-      $has_parents = (bool)idx($parent_map, $task->getPHID());
-      $has_subtasks = (bool)idx($subtask_map, $task->getPHID());
-
       $parents_uri = urisprintf(
         '/?subtaskIDs=%d#R',
         $task->getID());
@@ -143,7 +156,7 @@ final class ManiphestTaskDetailController extends ManiphestController {
       $graph_menu = id(new PHUIButtonView())
         ->setTag('a')
         ->setIcon('fa-search')
-        ->setText(pht('Search...'))
+        ->setText($search_text)
         ->setDropdownMenu($dropdown_menu);
 
       $graph_header = id(new PHUIHeaderView())

src/infrastructure/graph/ManiphestTaskGraph.php

@@ -148,4 +148,16 @@ final class ManiphestTaskGraph
 
     return $this->seedMaps[$type];
   }
+
+  protected function newEllipsisRow() {
+    return array(
+      null,
+      null,
+      null,
+      null,
+      pht("\xC2\xB7 \xC2\xB7 \xC2\xB7"),
+    );
+  }
+
+
 }

src/infrastructure/graph/PhabricatorObjectGraph.php

@@ -10,6 +10,7 @@ abstract class PhabricatorObjectGraph
   private $objects;
   private $loadEntireGraph = false;
   private $limit;
+  private $adjacent;
 
   public function setViewer(PhabricatorUser $viewer) {
     $this->viewer = $viewer;
@@ -33,6 +34,15 @@ abstract class PhabricatorObjectGraph
     return $this->limit;
   }
 
+  final public function setRenderOnlyAdjacentNodes($adjacent) {
+    $this->adjacent = $adjacent;
+    return $this;
+  }
+
+  final public function getRenderOnlyAdjacentNodes() {
+    return $this->adjacent;
+  }
+
   abstract protected function getEdgeTypes();
   abstract protected function getParentEdgeType();
   abstract protected function newQuery();
@@ -40,6 +50,12 @@ abstract class PhabricatorObjectGraph
   abstract protected function newTable(AphrontTableView $table);
   abstract protected function isClosed($object);
 
+  protected function newEllipsisRow() {
+    return array(
+      '...',
+    );
+  }
+
   final public function setSeedPHID($phid) {
     $this->seedPHID = $phid;
     $this->edgeReach[$phid] = array_fill_keys($this->getEdgeTypes(), true);
@@ -139,6 +155,32 @@ abstract class PhabricatorObjectGraph
 
     $ancestry = $this->getEdges($this->getParentEdgeType());
 
+    $only_adjacent = $this->getRenderOnlyAdjacentNodes();
+    if ($only_adjacent) {
+      $adjacent = array(
+        $this->getSeedPHID() => $this->getSeedPHID(),
+      );
+
+      foreach ($this->getEdgeTypes() as $edge_type) {
+        $map = $this->getEdges($edge_type);
+        $direct = idx($map, $this->getSeedPHID(), array());
+        $adjacent += array_fuse($direct);
+      }
+
+      foreach ($ancestry as $key => $list) {
+        if (!isset($adjacent[$key])) {
+          unset($ancestry[$key]);
+          continue;
+        }
+
+        foreach ($list as $list_key => $item) {
+          if (!isset($adjacent[$item])) {
+            unset($ancestry[$key][$list_key]);
+          }
+        }
+      }
+    }
+
     $objects = $this->newQuery()
       ->setViewer($viewer)
       ->withPHIDs(array_keys($ancestry))
@@ -157,6 +199,12 @@ abstract class PhabricatorObjectGraph
     $ii = 0;
     $rows = array();
     $rowc = array();
+
+    if ($only_adjacent) {
+      $rows[] = $this->newEllipsisRow();
+      $rowc[] = 'more';
+    }
+
     foreach ($ancestry as $phid => $ignored) {
       $object = idx($objects, $phid);
       $rows[] = $this->newTableRow($phid, $object, $traces[$ii++]);
@@ -181,6 +229,11 @@ abstract class PhabricatorObjectGraph
       $rowc[] = $classes;
     }
 
+    if ($only_adjacent) {
+      $rows[] = $this->newEllipsisRow();
+      $rowc[] = 'more';
+    }
+
     $table = id(new AphrontTableView($rows))
       ->setClassName('object-graph-table')
       ->setRowClasses($rowc);