Improve some Spaces behaviors

Summary:
Ref T8449. Try out some more subtle behaviors:

  - Make the "Space" control part of the policy control, so the UI shows "Visible To: [Space][Policy]". I think this helps make the role of spaces more clear. It also makes them easier to implement.
  - Don't show the default space in headers: instead, show nothing.
  - If the user has access to only one space, pretend spaces don't exist (no edit controls, no header stuff).

This might be confusing, but I think most of the time it will all align fairly well with user expectation.

Test Plan:
  - Viewed a list of pastes (saw Space with non-default space, no space with default space, no space with user in only one space).
  - Viewed a paste (saw Space with non-default space, saw no space with default space, saw no space with user in only one space).
  - Edited spaces on objects (control as privileged user, no control as locked user).
  - Created a new paste in a space (got space select as privileged user, no select as locked user).

Reviewers: chad, btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T8449

Differential Revision: https://secure.phabricator.com/D13229

src/applications/spaces/query/PhabricatorSpacesNamespaceQuery.php

@@ -90,6 +90,17 @@ final class PhabricatorSpacesNamespaceQuery
     return (bool)self::getAllSpaces();
   }
 
+  public static function getViewerSpacesExist(PhabricatorUser $viewer) {
+    if (!self::getSpacesExist()) {
+      return false;
+    }
+
+    // If the viewer has access to only one space, pretend spaces simply don't
+    // exist.
+    $spaces = self::getViewerSpaces($viewer);
+    return (count($spaces) > 1);
+  }
+
   public static function getAllSpaces() {
     $cache = PhabricatorCaches::getRequestCache();
     $cache_key = self::KEY_ALL;

src/applications/spaces/view/PHUISpacesNamespaceContextView.php

@@ -21,7 +21,20 @@ final class PHUISpacesNamespaceContextView extends AphrontView {
       return null;
     }
 
+    // If the viewer can't see spaces, pretend they don't exist.
     $viewer = $this->getUser();
+    if (!PhabricatorSpacesNamespaceQuery::getViewerSpacesExist($viewer)) {
+      return null;
+    }
+
+    // If this is the default space, don't show a space label.
+    $default = PhabricatorSpacesNamespaceQuery::getDefaultSpace();
+    if ($default) {
+      if ($default->getPHID() == $space_phid) {
+        return null;
+      }
+    }
+
     return phutil_tag(
       'span',
       array(

src/applications/spaces/view/PhabricatorSpacesControl.php

@@ -1,49 +0,0 @@
-<?php
-
-final class PhabricatorSpacesControl extends AphrontFormControl {
-
-  private $object;
-
-  protected function shouldRender() {
-    // Render this control only if some Spaces exist.
-    return PhabricatorSpacesNamespaceQuery::getAllSpaces();
-  }
-
-  public function setObject(PhabricatorSpacesInterface $object) {
-    $this->object = $object;
-    return $this;
-  }
-
-  protected function getCustomControlClass() {
-    return '';
-  }
-
-  protected function getOptions() {
-    $viewer = $this->getUser();
-    $viewer_spaces = PhabricatorSpacesNamespaceQuery::getViewerSpaces($viewer);
-
-    $map = mpull($viewer_spaces, 'getNamespaceName', 'getPHID');
-    asort($map);
-
-    return $map;
-  }
-
-  protected function renderInput() {
-    $viewer = $this->getUser();
-
-    $this->setLabel(pht('Space'));
-
-    $value = $this->getValue();
-    if ($value === null) {
-      $value = $viewer->getDefaultSpacePHID();
-    }
-
-    return AphrontFormSelectControl::renderSelectTag(
-      $value,
-      $this->getOptions(),
-      array(
-        'name' => $this->getName(),
-      ));
-  }
-
-}