Provide URI/API support for querying subtasks/parents of a particular task

Summary:
Ref T8126. Ref T4788. This adds a way to query by parent or subtask.

I plan to link to this from the task graph (e.g., {nav View > Search Subtasks} or similar, in a dropdown on the "Task Graph" element) as a way to let us bail out if tasks have 300 subtasks and send the user to a big query result list. That'll give us more flexibility to tailor the UI for reasonable numbers of tasks.

There's no UI for this unless you specify a query yourself, so the only ways to get to it are:

  - Manually put `?parentIDs=...` into the URI.
  - Use the API.
  - Future link from task graphs.

It doesn't seem too useful to me on its own, outside of the context of links from tasks.

Test Plan:
  - Manually put `?parentIDs=...` and `?subtaskIDs=...` into Maniphest query UI, got expected results.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T4788, T8126

Differential Revision: https://secure.phabricator.com/D16341

src/applications/maniphest/query/ManiphestTaskQuery.php

@@ -22,6 +22,8 @@ final class ManiphestTaskQuery extends PhabricatorCursorPagedPolicyAwareQuery {
   private $bridgedObjectPHIDs;
   private $hasOpenParents;
   private $hasOpenSubtasks;
+  private $parentTaskIDs;
+  private $subtaskIDs;
 
   private $fullTextSearch   = '';
 
@@ -161,6 +163,16 @@ final class ManiphestTaskQuery extends PhabricatorCursorPagedPolicyAwareQuery {
     return $this;
   }
 
+  public function withParentTaskIDs(array $ids) {
+    $this->parentTaskIDs = $ids;
+    return $this;
+  }
+
+  public function withSubtaskIDs(array $ids) {
+    $this->subtaskIDs = $ids;
+    return $this;
+  }
+
   public function withDateCreatedBefore($date_created_before) {
     $this->dateCreatedBefore = $date_created_before;
     return $this;
@@ -512,10 +524,11 @@ final class ManiphestTaskQuery extends PhabricatorCursorPagedPolicyAwareQuery {
     $edge_table = PhabricatorEdgeConfig::TABLE_NAME_EDGE;
     $task_table = $this->newResultObject()->getTableName();
 
+    $parent_type = ManiphestTaskDependedOnByTaskEdgeType::EDGECONST;
+    $subtask_type = ManiphestTaskDependsOnTaskEdgeType::EDGECONST;
+
     $joins = array();
     if ($this->hasOpenParents !== null) {
-      $parent_type = ManiphestTaskDependedOnByTaskEdgeType::EDGECONST;
-
       if ($this->hasOpenParents) {
         $join_type = 'JOIN';
       } else {
@@ -539,8 +552,6 @@ final class ManiphestTaskQuery extends PhabricatorCursorPagedPolicyAwareQuery {
     }
 
     if ($this->hasOpenSubtasks !== null) {
-      $subtask_type = ManiphestTaskDependsOnTaskEdgeType::EDGECONST;
-
       if ($this->hasOpenSubtasks) {
         $join_type = 'JOIN';
       } else {
@@ -602,6 +613,36 @@ final class ManiphestTaskQuery extends PhabricatorCursorPagedPolicyAwareQuery {
         break;
     }
 
+    if ($this->parentTaskIDs !== null) {
+      $joins[] = qsprintf(
+        $conn,
+        'JOIN %T e_has_parent
+          ON e_has_parent.src = task.phid
+          AND e_has_parent.type = %d
+         JOIN %T has_parent
+           ON e_has_parent.dst = has_parent.phid
+           AND has_parent.id IN (%Ld)',
+        $edge_table,
+        $parent_type,
+        $task_table,
+        $this->parentTaskIDs);
+    }
+
+    if ($this->subtaskIDs !== null) {
+      $joins[] = qsprintf(
+        $conn,
+        'JOIN %T e_has_subtask
+          ON e_has_subtask.src = task.phid
+          AND e_has_subtask.type = %d
+         JOIN %T has_subtask
+           ON e_has_subtask.dst = has_subtask.phid
+           AND has_subtask.id IN (%Ld)',
+        $edge_table,
+        $subtask_type,
+        $task_table,
+        $this->subtaskIDs);
+    }
+
     $joins[] = parent::buildJoinClauseParts($conn);
 
     return $joins;
@@ -611,6 +652,8 @@ final class ManiphestTaskQuery extends PhabricatorCursorPagedPolicyAwareQuery {
     $joined_multiple_rows =
       ($this->hasOpenParents !== null) ||
       ($this->hasOpenSubtasks !== null) ||
+      ($this->parentTaskIDs !== null) ||
+      ($this->subtaskIDs !== null) ||
       $this->shouldGroupQueryResultRows();
 
     $joined_project_name = ($this->groupBy == self::GROUP_PROJECT);

src/applications/maniphest/query/ManiphestTaskSearchEngine.php

@@ -92,6 +92,14 @@ final class ManiphestTaskSearchEngine
           pht('(Show All)'),
           pht('Show Only Tasks With Open Subtasks'),
           pht('Show Only Tasks Without Open Subtasks')),
+      id(new PhabricatorIDsSearchField())
+        ->setLabel(pht('Parent IDs'))
+        ->setKey('parentIDs')
+        ->setAliases(array('parentID')),
+      id(new PhabricatorIDsSearchField())
+        ->setLabel(pht('Subtask IDs'))
+        ->setKey('subtaskIDs')
+        ->setAliases(array('subtaskID')),
       id(new PhabricatorSearchSelectField())
         ->setLabel(pht('Group By'))
         ->setKey('group')
@@ -125,6 +133,8 @@ final class ManiphestTaskSearchEngine
       'fulltext',
       'hasParents',
       'hasSubtasks',
+      'parentIDs',
+      'subtaskIDs',
       'group',
       'order',
       'ids',
@@ -196,6 +206,14 @@ final class ManiphestTaskSearchEngine
       $query->withFullTextSearch($map['fulltext']);
     }
 
+    if ($map['parentIDs']) {
+      $query->withParentTaskIDs($map['parentIDs']);
+    }
+
+    if ($map['subtaskIDs']) {
+      $query->withSubtaskIDs($map['subtaskIDs']);
+    }
+
     $group = idx($map, 'group');
     $group = idx($this->getGroupValues(), $group);
     if ($group) {