From 85c953ebe4a6fef332158fd757d97c5a58682d3a Mon Sep 17 00:00:00 2001
From: epriestley <git@epriestley.com>
Date: Tue, 17 May 2022 16:15:03 -0700
Subject: [PATCH] Fix a PHP 8.1 repository marker issue in Mercurial

Summary:
Ref T13588. "arc-ls-markers" emits a "branch-state" marker so callers can identify which branch is active in the working copy.

This marker doesn't have an associated commit, so trying to generate a display name fails under stricter PHP 8.1 rules when we try to `substr(null, ...)`.

Don't attempt to generate a display name for markers with no commit hash.

Test Plan:
  - Ran `arc branches` under PHP 8.1 in a Mercurial repository.
  - Before: fatal.
  - After: sensible output.

Maniphest Tasks: T13588

Differential Revision: https://secure.phabricator.com/D21825
---
 src/repository/marker/ArcanistRepositoryMarkerQuery.php | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/repository/marker/ArcanistRepositoryMarkerQuery.php b/src/repository/marker/ArcanistRepositoryMarkerQuery.php
index e72ea78f..74e1cdf8 100644
--- a/src/repository/marker/ArcanistRepositoryMarkerQuery.php
+++ b/src/repository/marker/ArcanistRepositoryMarkerQuery.php
@@ -64,8 +64,10 @@ abstract class ArcanistRepositoryMarkerQuery
       $marker->attachWorkingCopyStateRef($state_ref);
 
       $hash = $marker->getCommitHash();
-      $hash = $api->getDisplayHash($hash);
-      $marker->setDisplayHash($hash);
+      if ($hash !== null) {
+        $hash = $api->getDisplayHash($hash);
+        $marker->setDisplayHash($hash);
+      }
     }
 
     $types = $this->markerTypes;