phacility/phabricator · error · Exception

Unexpected number of output lines from "git cat-file" when p

Error message

Unexpected number of output lines from "git cat-file" when processing commit ("%s").

What it means

DiffusionLowLevelFilesizeQuery computes the size of every file changed in a Git commit. It maps each changed path to its new blob hash via git diff-tree, then pipes the distinct hashes into 'git cat-file --batch-check=%(objectsize)' and consumes exactly one output line per hash. If cat-file returns fewer lines than hashes submitted, entries remain unconsumed in $check_paths and this exception is thrown for the commit identifier.

Source

Thrown at src/applications/diffusion/query/lowlevel/DiffusionLowLevelFilesizeQuery.php:115

    $future->write(implode("\n", array_keys($check_paths)));

    $size_lines = id(new LinesOfALargeExecFuture($future))
      ->setDelimiter("\n");
    foreach ($size_lines as $line) {
      $object_size = (int)$line;

      $object_hash = head_key($check_paths);
      $path_names = $check_paths[$object_hash];
      unset($check_paths[$object_hash]);

      foreach ($path_names as $path_name) {
        $path_sizes[$path_name] = $object_size;
      }
    }

    if ($check_paths) {
      throw new Exception(
        pht(
          'Unexpected number of output lines from "git cat-file" when '.
          'processing commit ("%s").',
          $identifier));
    }

    return $path_sizes;
  }

}

View on GitHub (pinned to 5720a38cfe)

Solutions

Run 'git fsck' inside the repository's local path as the daemon user to locate missing or corrupt objects
Repair by deleting the local working copy and re-cloning: bin/repository update <callsign> (or trigger re-clone from Diffusion -> Manage)
Verify the daemon user can read every file under the local path; permission holes mimic corruption
Retry after any in-flight git gc finishes; if it persists, the commit's blobs are genuinely absent and only a re-clone fixes it

Defensive patterns

Strategy: try-catch

Validate before calling

// Pre-verify the commit's blobs exist before the size query
$future = $repository->getLocalCommandFuture('cat-file -e %s', $blob_hash);
list(, $err) = $future->resolve();
if ($err) {
  // object missing: skip size rendering for this commit
}

Try / catch

try {
  $sizes = id(new DiffusionLowLevelFilesizeQuery())
    ->setRepository($repository)
    ->withIdentifier($commit_identifier)
    ->executeQuery();
} catch (Exception $ex) {
  $sizes = array(); // sizes are cosmetic: degrade gracefully and log for triage
  phlog($ex);
}

Prevention

Treat file sizes as optional data so a corrupt object never breaks commit rendering
Run git fsck after any storage incident and re-clone damaged repositories
Keep daemon-side gc/prune from racing heavy browsing windows

When it happens

Trigger: Executing DiffusionLowLevelFilesizeQuery (used when rendering changed-file sizes for a commit page) on a commit whose blob objects are missing from the local clone, so cat-file emits no record for them; also when the object store is corrupted or being rewritten by a concurrent gc/repack.

Common situations: Corrupt or partially-pruned local clones after disk problems, interrupted clones, broken alternates, or a git gc racing the query. Typically one specific commit fails while neighbors render fine.

Related errors

AI-assisted analysis of phacility/phabricator@5720a38cfe (2026-08-21). Data as JSON: /api/errors/7ac7a3e926dc440c. Report an issue: GitHub.