From 614e6756ee8b54b0611613f2fb0d1613384ab860 Mon Sep 17 00:00:00 2001
From: Valerio Bozzolan <nsa+gitspam@succhia.cz>
Date: Mon, 15 Dec 2025 12:31:03 +0100
Subject: [PATCH] Fix PHP 8.1 "strlen(null)" exception when using Diffusion
 'Compare'

Summary:
The method 'getSymbolicCommit()' can return null, and that value is not passed to strlen() anymore.

Closes T16297

Test Plan:
Visit the Diffusion page 'Compare' page without inputs, no warnings anymore from Dark console:

http://phorge.localhost/diffusion/1/compare/

Visit all the Diffusion page 'Compare' page of all your branches, they still work:

http://phorge.localhost/diffusion/1/branches/master/

(e.g. tested with branches 'master', 'devops', 'weblate', 'crashtest')

Compare two real branches like 'master' and 'test' or whatever, from this page, and it still works:

http://phorge.localhost/diffusion/1/compare/

Invert the branches. It still works.

Reviewers: O1 Blessed Committers, aklapper

Reviewed By: O1 Blessed Committers, aklapper

Subscribers: aklapper, tobiaswiese, Matthew, Cigaryno

Maniphest Tasks: T16297

Differential Revision: https://we.phorge.it/D26422
---
 .../diffusion/controller/DiffusionCompareController.php     | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/applications/diffusion/controller/DiffusionCompareController.php b/src/applications/diffusion/controller/DiffusionCompareController.php
index 26d888dfb2..5e18c1db88 100644
--- a/src/applications/diffusion/controller/DiffusionCompareController.php
+++ b/src/applications/diffusion/controller/DiffusionCompareController.php
@@ -27,14 +27,14 @@ final class DiffusionCompareController extends DiffusionController {
         ->addCancelButton($this->getApplicationURI(), pht('Okay'));
     }
 
-    $head_ref = $request->getStr('head');
-    $against_ref = $request->getStr('against');
+    $head_ref = $request->getStr('head', '');
+    $against_ref = $request->getStr('against', '');
 
     $must_prompt = false;
     if (!$request->isFormPost()) {
       if (!strlen($head_ref)) {
         $head_ref = $drequest->getSymbolicCommit();
-        if (!strlen($head_ref)) {
+        if (!phutil_nonempty_string($head_ref)) {
           $head_ref = $drequest->getBranch();
         }
       }
-- 
2.51.2