Support PhabricatorSpacesInterface in ApplicationSearch UI

Summary: Ref T8441. Does what it says, provided other conditions (like using the new SearchField stuff) are fulfilled.

Test Plan:
{F473836}

{F473837}

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T8441

Differential Revision: https://secure.phabricator.com/D13171

src/applications/spaces/phid/PhabricatorSpacesNamespacePHIDType.php

@@ -9,6 +9,10 @@ final class PhabricatorSpacesNamespacePHIDType
     return pht('Space');
   }
 
+  public function getPHIDTypeApplicationClass() {
+    return 'PhabricatorSpacesApplication';
+  }
+
   public function newObject() {
     return new PhabricatorSpacesNamespace();
   }

src/applications/spaces/query/PhabricatorSpacesNamespaceQuery.php

@@ -86,6 +86,10 @@ final class PhabricatorSpacesNamespaceQuery
       ));
   }
 
+  public static function getSpacesExist() {
+    return (bool)self::getAllSpaces();
+  }
+
   public static function getAllSpaces() {
     $cache = PhabricatorCaches::getRequestCache();
     $cache_key = self::KEY_ALL;

src/applications/spaces/typeahead/PhabricatorSpacesNamespaceDatasource.php

@@ -0,0 +1,32 @@
+<?php
+
+final class PhabricatorSpacesNamespaceDatasource
+  extends PhabricatorTypeaheadDatasource {
+
+  public function getBrowseTitle() {
+    return pht('Browse Spaces');
+  }
+
+  public function getPlaceholderText() {
+    return pht('Type a space name...');
+  }
+
+  public function getDatasourceApplicationClass() {
+    return 'PhabricatorSpacesApplication';
+  }
+
+  public function loadResults() {
+    $query = id(new PhabricatorSpacesNamespaceQuery());
+
+    $spaces = $this->executeQuery($query);
+    $results = array();
+    foreach ($spaces as $space) {
+      $results[] = id(new PhabricatorTypeaheadResult())
+        ->setName($space->getNamespaceName())
+        ->setPHID($space->getPHID());
+    }
+
+    return $this->filterResultsAgainstTokens($results);
+  }
+
+}