viewproperties: fall back to .directory when xattr space is exhausted

When saving view properties to extended attributes failed with NoSpace,
the code cleared the xattr entry and returned without writing anything
to disk. The .directory fallback file was never created, silently
losing the user's view settings.

Fix by copying the current settings into a file-backed KConfig pointing
to .directory whenever the xattr write returns NoSpace. The copy uses
KConfigGroup::copyTo per group (not KConfig::copyFrom, which replaces
the entire entry map) so that unrelated groups already present in
.directory — such as a [Desktop Entry] group carrying a custom folder
icon — are left untouched by sync().

2 files changed, 122 insertions, 1 deletions

diff --git a/src/tests/viewpropertiestest.cpp b/src/tests/viewpropertiestest.cpp
index c4cc9cc41..101fff707 100644
--- a/src/tests/viewpropertiestest.cpp
+++ b/src/tests/viewpropertiestest.cpp
@@ -13,6 +13,10 @@
 #include <QStorageInfo>
 #include <QTest>
 
+#ifdef Q_OS_UNIX
+#include <unistd.h>
+#endif
+
 class ViewPropertiesTest : public QObject
 {
     Q_OBJECT
@@ -29,6 +33,8 @@ private Q_SLOTS:
     void testParamMigrationToFileAttrKeepDirectory();
     void testGlobalDefaultConfigFromDirectory();
     void testExtendedAttributeFull();
+    void testExtendedAttributeFullKeepDirectory();
+    void testExtendedAttributeFullWriteFailure();
     void testUseAsDefaultViewSettings();
     void testUseAsCustomDefaultViewSettings();
     void testSpecialFolderPropsPreservedWithGlobalViewProps();
@@ -337,6 +343,107 @@ void ViewPropertiesTest::testExtendedAttributeFull()
     }
 }
 
+void ViewPropertiesTest::testExtendedAttributeFullKeepDirectory()
+{
+#ifndef Q_OS_UNIX
+    QSKIP("Only unix is supported, for this test");
+#endif
+    const QString dotDirectoryFilePath = m_testDir->url().toLocalFile() + "/.directory";
+    QVERIFY(!QFile::exists(dotDirectoryFilePath));
+
+    // Pre-populate .directory with a Dolphin group and a non-Dolphin group (e.g. folder icon).
+    const char *initialContent =
+        "[Desktop Entry]\n"
+        "Icon=folder-pictures\n"
+        "\n"
+        "[Dolphin]\n"
+        "Version=4\n"
+        "ViewMode=0\n";
+    {
+        QFile f(dotDirectoryFilePath);
+        QVERIFY(f.open(QIODevice::WriteOnly | QIODevice::Text | QIODevice::Truncate));
+        f.write(initialContent);
+    }
+
+    KFileMetaData::UserMetaData metadata(m_testDir->url().toLocalFile());
+    if (!metadata.isSupported()) {
+        QSKIP("need extended attribute/filesystem metadata to be useful");
+    }
+
+    QStorageInfo storageInfo(m_testDir->url().toLocalFile());
+    const auto blockSize = storageInfo.blockSize();
+
+    KFileMetaData::UserMetaData::Error result;
+    result = metadata.setAttribute("data", QString(blockSize - 50, 'a'));
+    if (result != KFileMetaData::UserMetaData::NoSpace) {
+        QSKIP("File system supports metadata bigger than file system block size");
+    }
+    result = metadata.setAttribute("data", QString(blockSize - 60, 'a'));
+    QCOMPARE(result, KFileMetaData::UserMetaData::NoError);
+
+    QScopedPointer<ViewProperties> props(new ViewProperties(m_testDir->url()));
+    props->setSortRole("someNewSortRole");
+    props.reset();
+
+    // xattr write should have failed with NoSpace — attribute must be empty
+    QVERIFY(metadata.attribute(QStringLiteral("kde.fm.viewproperties#1")).isEmpty());
+    // .directory must still exist
+    QVERIFY(QFile::exists(dotDirectoryFilePath));
+
+    KConfig viewSettings(dotDirectoryFilePath, KConfig::SimpleConfig);
+    // Dolphin settings were updated
+    QCOMPARE(viewSettings.group(QStringLiteral("Dolphin")).readEntry("SortRole"), QStringLiteral("someNewSortRole"));
+    // Non-Dolphin groups must be preserved
+    QVERIFY(viewSettings.hasGroup(QStringLiteral("Desktop Entry")));
+    QCOMPARE(viewSettings.group(QStringLiteral("Desktop Entry")).readEntry("Icon"), QStringLiteral("folder-pictures"));
+}
+
+void ViewPropertiesTest::testExtendedAttributeFullWriteFailure()
+{
+#ifndef Q_OS_UNIX
+    QSKIP("Only unix is supported, for this test");
+#else
+    if (getuid() == 0) {
+        QSKIP("Running as root — permission checks are not enforced");
+    }
+
+    const QString testDirPath = m_testDir->url().toLocalFile();
+    const QString dotDirectoryFilePath = testDirPath + "/.directory";
+    QVERIFY(!QFile::exists(dotDirectoryFilePath));
+
+    KFileMetaData::UserMetaData metadata(testDirPath);
+    if (!metadata.isSupported()) {
+        QSKIP("need extended attribute/filesystem metadata to be useful");
+    }
+
+    QStorageInfo storageInfo(testDirPath);
+    const auto blockSize = storageInfo.blockSize();
+
+    KFileMetaData::UserMetaData::Error result;
+    result = metadata.setAttribute("data", QString(blockSize - 50, 'a'));
+    if (result != KFileMetaData::UserMetaData::NoSpace) {
+        QSKIP("File system supports metadata bigger than file system block size");
+    }
+    result = metadata.setAttribute("data", QString(blockSize - 60, 'a'));
+    QCOMPARE(result, KFileMetaData::UserMetaData::NoError);
+
+    // Make the test directory read-only so writing .directory fails
+    QVERIFY(QFile::setPermissions(testDirPath, QFileDevice::ReadOwner | QFileDevice::ExeOwner));
+    auto restorePermissions = qScopeGuard([&testDirPath] {
+        QFile::setPermissions(testDirPath, QFileDevice::ReadOwner | QFileDevice::WriteOwner | QFileDevice::ExeOwner);
+    });
+
+    // This must not crash even though both xattr and .directory are unwritable
+    QScopedPointer<ViewProperties> props(new ViewProperties(m_testDir->url()));
+    props->setSortRole("someNewSortRole");
+    props.reset();
+
+    // Neither xattr nor .directory should have been written
+    QVERIFY(metadata.attribute(QStringLiteral("kde.fm.viewproperties#1")).isEmpty());
+    QVERIFY(!QFile::exists(dotDirectoryFilePath));
+#endif
+}
+
 void ViewPropertiesTest::testUseAsDefaultViewSettings()
 {
     // Create a global viewproperties folder
diff --git a/src/views/viewproperties.cpp b/src/views/viewproperties.cpp
index c5e53586c..9cd834991 100644
--- a/src/views/viewproperties.cpp
+++ b/src/views/viewproperties.cpp
@@ -640,10 +640,24 @@ void ViewProperties::save()
             // free the space used by viewproperties from the file metadata
             metaData.setAttribute(MetaDataKey, QString());
             qCWarning(DolphinDebug) << "could not save viewproperties to extended attributes for dir " << m_filePath << ", no space available in attributes";
+            // xattr space exhausted — fall back to .directory file.
+            // Copy only the Dolphin-managed groups into the existing file using
+            // KConfigGroup::copyTo so that unrelated groups (e.g. [Desktop Entry]
+            // with a custom folder icon) are left untouched by sync().
+            const QString settingsFile = m_filePath + QDir::separator() + ViewPropertiesFileName;
+            KConfig fileConfig(settingsFile, KConfig::SimpleConfig);
+            for (const QString &group : m_node->config()->groupList()) {
+                KConfigGroup srcGrp(m_node->config(), group);
+                KConfigGroup dstGrp(&fileConfig, group);
+                srcGrp.copyTo(&dstGrp);
+            }
+            if (!fileConfig.sync()) {
+                qCWarning(DolphinDebug) << "could not save viewproperties to .directory for" << m_filePath;
+            }
         } else {
             qCWarning(DolphinDebug) << "could not save viewproperties to extended attributes for dir " << m_filePath << "error:" << result;
         }
-        // keep .directory file
+        m_changedProps = false;
         return;
     }
     cleanDotDirectoryFile();