Simplify "builtin file" management and recover from races

Summary:
Fixes T11307. Fixes T8124. Currently, builtin files are tracked by using a special transform with an invalid source ID.

Just use a dedicated column instead. The transform thing is too clever/weird/hacky and exposes us to issues with the "file" and "transform" tables getting out of sync (possibly the issue in T11307?) and with race conditions.

Test Plan:
  - Loaded profile "edit picture" page, saw builtins.
  - Deleted all builtin files, put 3 second sleep in the storage engine write, loaded profile page in two windows.
    - Before patch: one of them failed with a race.
    - After patch: both of them loaded.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T8124, T11307

Differential Revision: https://secure.phabricator.com/D16271

resources/sql/autopatches/20160711.files.01.builtin.sql

@@ -0,0 +1,2 @@
+ALTER TABLE {$NAMESPACE}_file.file
+  ADD builtinKey VARCHAR(64) COLLATE {$COLLATE_TEXT};

resources/sql/autopatches/20160711.files.02.builtinkey.sql

@@ -0,0 +1,2 @@
+ALTER TABLE {$NAMESPACE}_file.file
+  ADD UNIQUE KEY `key_builtin` (builtinKey);

src/applications/files/query/PhabricatorFileQuery.php

@@ -16,6 +16,7 @@ final class PhabricatorFileQuery
   private $names;
   private $isPartial;
   private $needTransforms;
+  private $builtinKeys;
 
   public function withIDs(array $ids) {
     $this->ids = $ids;
@@ -47,6 +48,11 @@ final class PhabricatorFileQuery
     return $this;
   }
 
+  public function withBuiltinKeys(array $keys) {
+    $this->builtinKeys = $keys;
+    return $this;
+  }
+
   /**
    * Select files which are transformations of some other file. For example,
    * you can use this query to find previously generated thumbnails of an image
@@ -384,6 +390,13 @@ final class PhabricatorFileQuery
         (int)$this->isPartial);
     }
 
+    if ($this->builtinKeys !== null) {
+      $where[] = qsprintf(
+        $conn,
+        'builtinKey IN (%Ls)',
+        $this->builtinKeys);
+    }
+
     return $where;
   }
 

src/applications/files/storage/PhabricatorFile.php

@@ -42,6 +42,7 @@ final class PhabricatorFile extends PhabricatorFileDAO
   protected $contentHash;
   protected $metadata = array();
   protected $mailKey;
+  protected $builtinKey;
 
   protected $storageEngine;
   protected $storageFormat;
@@ -94,6 +95,7 @@ final class PhabricatorFile extends PhabricatorFileDAO
         'isExplicitUpload' => 'bool?',
         'mailKey' => 'bytes20',
         'isPartial' => 'bool',
+        'builtinKey' => 'text64?',
       ),
       self::CONFIG_KEY_SCHEMA => array(
         'key_phid' => null,
@@ -116,6 +118,10 @@ final class PhabricatorFile extends PhabricatorFileDAO
         'key_partial' => array(
           'columns' => array('authorPHID', 'isPartial'),
         ),
+        'key_builtin' => array(
+          'columns' => array('builtinKey'),
+          'unique' => true,
+        ),
       ),
     ) + parent::getConfiguration();
   }
@@ -1070,19 +1076,11 @@ final class PhabricatorFile extends PhabricatorFileDAO
   public static function loadBuiltins(PhabricatorUser $user, array $builtins) {
     $builtins = mpull($builtins, null, 'getBuiltinFileKey');
 
-    $specs = array();
-    foreach ($builtins as $key => $buitin) {
-      $specs[] = array(
-        'originalPHID' => PhabricatorPHIDConstants::PHID_VOID,
-        'transform'    => $key,
-      );
-    }
-
     // NOTE: Anyone is allowed to access builtin files.
 
     $files = id(new PhabricatorFileQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
-      ->withTransforms($specs)
+      ->withBuiltinKeys(array_keys($builtins))
       ->execute();
 
     $results = array();
@@ -1109,12 +1107,21 @@ final class PhabricatorFile extends PhabricatorFileDAO
       );
 
       $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
-        $file = self::newFromFileData($data, $params);
-        $xform = id(new PhabricatorTransformedFile())
-          ->setOriginalPHID(PhabricatorPHIDConstants::PHID_VOID)
-          ->setTransform($key)
-          ->setTransformedPHID($file->getPHID())
-          ->save();
+        try {
+          $file = self::newFromFileData($data, $params);
+        } catch (AphrontDuplicateKeyQueryException $ex) {
+          $file = id(new PhabricatorFileQuery())
+            ->setViewer(PhabricatorUser::getOmnipotentUser())
+            ->withBuiltinKeys(array($key))
+            ->executeOne();
+          if (!$file) {
+            throw new Exception(
+              pht(
+                'Collided mid-air when generating builtin file "%s", but '.
+                'then failed to load the object we collided with.',
+                $key));
+          }
+        }
       unset($unguarded);
 
       $file->attachObjectPHIDs(array());
@@ -1289,6 +1296,7 @@ final class PhabricatorFile extends PhabricatorFileDAO
     $builtin = idx($params, 'builtin');
     if ($builtin) {
       $this->setBuiltinName($builtin);
+      $this->setBuiltinKey($builtin);
     }
 
     $profile = idx($params, 'profile');