Add information dialogs to adding project members if unsupported

Summary: If you try to join or add members to a parent project, we currently return 404. This instead adds an informational dialog. Fixes T11055

Test Plan: Click on Join Project and Add Members while on a Parent Project or Milestone.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T11055

Differential Revision: https://secure.phabricator.com/D16000

src/applications/project/controller/PhabricatorProjectMembersAddController.php

@@ -21,12 +21,17 @@ final class PhabricatorProjectMembersAddController
     }
 
     $this->setProject($project);
+    $done_uri = "/project/members/{$id}/";
 
     if (!$project->supportsEditMembers()) {
-      return new Aphront404Response();
+      $copy = pht('Parent projects and milestones do not support adding '.
-    }
+        'members. You can add members directly to any non-parent subproject.');
 
-    $done_uri = "/project/members/{$id}/";
+      return $this->newDialog()
+        ->setTitle(pht('Unsupported Project'))
+        ->appendParagraph($copy)
+        ->addCancelButton($done_uri);
+    }
 
     if ($request->isFormPost()) {
       $member_phids = $request->getArr('memberPHIDs');

src/applications/project/controller/PhabricatorProjectUpdateController.php

@@ -32,12 +32,18 @@ final class PhabricatorProjectUpdateController
       return new Aphront404Response();
     }
 
-    if (!$project->supportsEditMembers()) {
-      return new Aphront404Response();
-    }
-
     $done_uri = "/project/members/{$id}/";
 
+    if (!$project->supportsEditMembers()) {
+      $copy = pht('Parent projects and milestones do not support adding '.
+        'members. You can add members directly to any non-parent subproject.');
+
+      return $this->newDialog()
+        ->setTitle(pht('Unsupported Project'))
+        ->appendParagraph($copy)
+        ->addCancelButton($done_uri);
+    }
+
     if ($request->isFormPost()) {
       $edge_action = null;
       switch ($action) {