Simplify some logic in project controllers

Summary: Ref T10010. Several controlers currently have similar logic for handling tags and slugs, loading projects, and canonicalizing URIs. Clean it up a bit.

Test Plan:
  - Visited profile, boards, feed.
  - Visited by ID and by tag.
  - Visited by non-normal tag (redircted).
  - Visited by alternate tag (redirected).
  - Visited non-policy project by non-normal tag (redirected into policy error).

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10010

Differential Revision: https://secure.phabricator.com/D14890

src/applications/project/controller/PhabricatorProjectController.php

@@ -13,6 +13,72 @@ abstract class PhabricatorProjectController extends PhabricatorController {
     return $this->project;
   }
 
+  protected function loadProject() {
+    $viewer = $this->getViewer();
+    $request = $this->getRequest();
+
+    $id = $request->getURIData('id');
+    $slug = $request->getURIData('slug');
+
+    if ($slug) {
+      $normal_slug = PhabricatorSlug::normalizeProjectSlug($slug);
+      $is_abnormal = ($slug !== $normal_slug);
+      $normal_uri = "/tag/{$normal_slug}/";
+    } else {
+      $is_abnormal = false;
+    }
+
+    $query = id(new PhabricatorProjectQuery())
+      ->setViewer($viewer)
+      ->needMembers(true)
+      ->needWatchers(true)
+      ->needImages(true)
+      ->needSlugs(true);
+
+    if ($slug) {
+      $query->withSlugs(array($slug));
+    } else {
+      $query->withIDs(array($id));
+    }
+
+    $policy_exception = null;
+    try {
+      $project = $query->executeOne();
+    } catch (PhabricatorPolicyException $ex) {
+      $policy_exception = $ex;
+      $project = null;
+    }
+
+    if (!$project) {
+      // This project legitimately does not exist, so just 404 the user.
+      if (!$policy_exception) {
+        return new Aphront404Response();
+      }
+
+      // Here, the project exists but the user can't see it. If they are
+      // using a non-canonical slug to view the project, redirect to the
+      // canonical slug. If they're already using the canonical slug, rethrow
+      // the exception to give them the policy error.
+      if ($is_abnormal) {
+        return id(new AphrontRedirectResponse())->setURI($normal_uri);
+      } else {
+        throw $policy_exception;
+      }
+    }
+
+    // The user can view the project, but is using a noncanonical slug.
+    // Redirect to the canonical slug.
+    $primary_slug = $project->getPrimarySlug();
+    if ($slug && ($slug !== $primary_slug)) {
+      $primary_uri = "/tag/{$primary_slug}/";
+      return id(new AphrontRedirectResponse())->setURI($primary_uri);
+    }
+
+    $this->setProject($project);
+
+    return null;
+  }
+
   public function buildApplicationMenu() {
     return $this->buildSideNavView(true)->getMenu();
   }