Use a serialize()-based cache instead of a JSON-based cache for changesets

Summary: These are full of PhutilSafeHTML objects now, which are destroyed by JSON serialization.

Test Plan: Dropped cache, then reloaded pages.

Reviewers: vrana

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D4942

src/applications/differential/parser/DifferentialChangesetParser.php

@@ -63,7 +63,7 @@ final class DifferentialChangesetParser {
     return $this->disableCache;
   }
 
-  const CACHE_VERSION = 10;
+  const CACHE_VERSION = 11;
   const CACHE_MAX_SIZE = 8e6;
 
   const ATTR_GENERATED  = 'attr:generated';
@@ -270,7 +270,13 @@ final class DifferentialChangesetParser {
       return false;
     }
 
-    $data = json_decode($data['cache'], true);
+    if ($data['cache'][0] == '{') {
+      // This is likely an old-style JSON cache which we will not be able to
+      // deserialize.
+      return false;
+    }
+
+    $data = unserialize($data['cache']);
     if (!is_array($data) || !$data) {
       return false;
     }
@@ -340,7 +346,7 @@ final class DifferentialChangesetParser {
           break;
       }
     }
-    $cache = json_encode($cache);
+    $cache = serialize($cache);
 
     // We don't want to waste too much space by a single changeset.
     if (strlen($cache) > self::CACHE_MAX_SIZE) {