From 6556185b73ca1c32a76a7a012b3843f0bb11a292 Mon Sep 17 00:00:00 2001
From: Jyrki Gadinger <nilsding@nilsding.org>
Date: Mon, 16 Mar 2026 13:37:15 +0100
Subject: [PATCH] fix(filesystem): deal with win32 long paths when recursively
 removing folders

`std::filesystem::remove` etc. seem to behave the same way as the pure
win32-APIs: sometimes long paths work, sometimes they won't.  In this
case it seems to be able to deal with long UNC-style paths just fine ...

Resolves #9293

Signed-off-by: Jyrki Gadinger <nilsding@nilsding.org>
---
 src/libsync/filesystem.cpp |  8 +++++++-
 test/testfilesystem.cpp    | 22 ++++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/src/libsync/filesystem.cpp b/src/libsync/filesystem.cpp
index 3e65aed6b41fa..e27301c035f1b 100644
--- a/src/libsync/filesystem.cpp
+++ b/src/libsync/filesystem.cpp
@@ -312,7 +312,13 @@ bool FileSystem::removeRecursively(const QString &path,
         auto folderDeleteError = QString{};
 
         try {
-            if (!std::filesystem::remove(std::filesystem::path{fileInfo.filePath().toStdWString()})) {
+#ifdef Q_OS_WIN
+            // std::filesystem::remove does not handle paths greater than MAX_PATH, but it seems to be fine with the prefixed UNC paths ...
+            const auto fspath = std::filesystem::path{FileSystem::longWinPath(fileInfo.filePath()).toStdWString()};
+#else
+            const auto fspath = std::filesystem::path{fileInfo.filePath().toStdWString()};
+#endif
+            if (!std::filesystem::remove(fspath)) {
                 qCWarning(lcFileSystem()) << "File is already deleted" << fileInfo.filePath();
             }
         }
diff --git a/test/testfilesystem.cpp b/test/testfilesystem.cpp
index d3e5dc20b8a08..37abf3784f537 100644
--- a/test/testfilesystem.cpp
+++ b/test/testfilesystem.cpp
@@ -320,6 +320,28 @@ private Q_SLOTS:
         QCOMPARE_EQ(aclSizeAfterReadWrite.AclBytesInUse, aclSizeInitial.AclBytesInUse);
     }
 #endif
+
+    void testRecursiveDeletionLongPaths()
+    {
+        QTemporaryDir tempDir;
+        QDir tempQDir{tempDir.path()};
+
+        const auto makeLongPathSegment = [](const QString &base) -> QString {
+            QString baseSegment = base + " ";
+            return baseSegment + QString("0").repeated(200 - baseSegment.size());
+        };
+
+        tempQDir.mkpath("Folder 1 - short name but long single subfolder/" + makeLongPathSegment("Subfolder without accentued characters - padding"));
+        tempQDir.mkpath(makeLongPathSegment("Folder 2 - directly a very long name"));
+        auto folder3Path = u"Folder 3 - short name but long multiples subfolder"_s;
+        for (auto i = 0; i < 5; i++) {
+            folder3Path.append("/subfolder %1 - total length 40 characters"_L1.arg(QString::number(i + 1)));
+        }
+        tempQDir.mkpath(folder3Path);
+        tempQDir.mkpath("Folder 4 - short name");
+
+        QVERIFY(FileSystem::removeRecursively(tempDir.path()));
+    }
 };
 
 QTEST_GUILESS_MAIN(TestFileSystem)