Create utility method for moving entries from one group to another

This will become especially useful when moving state data from the config file
to a dedicated state data file.

Task: https://phabricator.kde.org/T12549

6 files changed, 91 insertions, 2 deletions

diff --git a/autotests/kconfigtest.cpp b/autotests/kconfigtest.cpp
index c3a68e42..00e7bbf0 100644
--- a/autotests/kconfigtest.cpp
+++ b/autotests/kconfigtest.cpp
@@ -1898,6 +1898,47 @@ void KConfigTest::testNewlines()
 #endif
 }
 
+void KConfigTest::testMoveValuesTo()
+{
+    QTemporaryFile file;
+    QVERIFY(file.open());
+    // Prepare kdeglobals
+    {
+        KConfig glob(QStringLiteral("kdeglobals"));
+        KConfigGroup general(&glob, "TestGroup");
+        general.writeEntry("GlobalKey", "PlsDeleteMe");
+        QVERIFY(glob.sync());
+    }
+
+    KConfigGroup grp = KSharedConfig::openConfig(file.fileName())->group("TestGroup");
+
+    grp.writeEntry("test1", "first_value");
+    grp.writeEntry("test_empty", "");
+    grp.writeEntry("other", "other_value");
+    grp.writePathEntry("my_path", QStringLiteral("~/somepath"));
+    // because this key is from the global file it should be explicitly deleted
+    grp.deleteEntry("GlobalKey");
+
+    QTemporaryFile targetFile;
+    QVERIFY(targetFile.open());
+    targetFile.close();
+    KConfigGroup targetGroup = KSharedConfig::openConfig(targetFile.fileName(), KConfig::SimpleConfig)->group("MoveToGroup");
+
+    grp.moveValuesTo({"test1", "test_empty", "does_not_exist", "my_path", "GlobalKey"}, targetGroup);
+    QVERIFY(grp.config()->isDirty());
+    QVERIFY(targetGroup.config()->isDirty());
+
+    QCOMPARE(grp.keyList(), QStringList{QStringLiteral("other")});
+    QStringList expectedKeyList{QStringLiteral("my_path"), QStringLiteral("test1"), QStringLiteral("test_empty")};
+    QCOMPARE(targetGroup.keyList(), expectedKeyList);
+    QCOMPARE(targetGroup.readEntry("test1"), QStringLiteral("first_value"));
+
+    targetGroup.sync();
+    QFile targetReadFile(targetFile.fileName());
+    targetReadFile.open(QFile::ReadOnly);
+    QVERIFY(targetReadFile.readAll().contains(QByteArray("my_path[$e]=~/somepath")));
+}
+
 void KConfigTest::testXdgListEntry()
 {
     QTemporaryFile file;
diff --git a/autotests/kconfigtest.h b/autotests/kconfigtest.h
index 9d519eda..f716bd70 100644
--- a/autotests/kconfigtest.h
+++ b/autotests/kconfigtest.h
@@ -64,6 +64,8 @@ private Q_SLOTS:
     void testQStringUtf8_data();
     void testQStringUtf8();
 
+    void testMoveValuesTo();
+
     void testSubGroup();
     void testAddConfigSources();
     void testWriteOnSync();
diff --git a/src/core/kconfig.cpp b/src/core/kconfig.cpp
index 506e3f90..03ab67d3 100644
--- a/src/core/kconfig.cpp
+++ b/src/core/kconfig.cpp
@@ -1010,14 +1010,19 @@ void KConfigPrivate::revertEntry(const QByteArray &group, const char *key, KConf
 
 QByteArray KConfigPrivate::lookupData(const QByteArray &group, const char *key, KEntryMap::SearchFlags flags) const
 {
+    return lookupInternalEntry(group, key, flags).mValue;
+}
+
+KEntry KConfigPrivate::lookupInternalEntry(const QByteArray &group, const char *key, KEntryMap::SearchFlags flags) const
+{
     if (bReadDefaults) {
         flags |= KEntryMap::SearchDefaults;
     }
     const auto it = entryMap.constFindEntry(group, key, flags);
     if (it == entryMap.constEnd()) {
-        return QByteArray();
+        return {};
     }
-    return it->mValue;
+    return it.value();
 }
 
 QString KConfigPrivate::lookupData(const QByteArray &group, const char *key, KEntryMap::SearchFlags flags, bool *expand) const
diff --git a/src/core/kconfig_p.h b/src/core/kconfig_p.h
index e5c9d869..60604477 100644
--- a/src/core/kconfig_p.h
+++ b/src/core/kconfig_p.h
@@ -34,8 +34,15 @@ public:
     bool canWriteEntry(const QByteArray &group, const char *key, bool isDefault = false) const;
     QString lookupData(const QByteArray &group, const char *key, KEntryMap::SearchFlags flags, bool *expand) const;
     QByteArray lookupData(const QByteArray &group, const char *key, KEntryMap::SearchFlags flags) const;
+    KEntry lookupInternalEntry(const QByteArray &group, const char *key, KEntryMap::SearchFlags flags) const;
 
     void putData(const QByteArray &group, const char *key, const QByteArray &value, KConfigBase::WriteConfigFlags flags, bool expand = false);
+    void setEntryData(const QByteArray &group, const char *key, const QByteArray &value, KEntryMap::EntryOptions flags)
+    {
+        if (entryMap.setEntry(group, key, value, flags)) {
+            bDirty = true;
+        }
+    }
     void revertEntry(const QByteArray &group, const char *key, KConfigBase::WriteConfigFlags flags);
     QStringList groupList(const QByteArray &group) const;
     // copies the entries from @p source to @p otherGroup changing all occurrences
diff --git a/src/core/kconfiggroup.cpp b/src/core/kconfiggroup.cpp
index a15c45eb..be1f2b0e 100644
--- a/src/core/kconfiggroup.cpp
+++ b/src/core/kconfiggroup.cpp
@@ -1257,3 +1257,29 @@ void KConfigGroup::reparent(KConfigBase *parent, WriteConfigFlags pFlags)
     oldGroup.copyTo(this, pFlags);
     oldGroup.deleteGroup(); // so that the entries with the old group name are deleted on sync
 }
+
+void KConfigGroup::moveValuesTo(const QList<const char *> &keys, KConfigGroup &other, WriteConfigFlags pFlags)
+{
+    Q_ASSERT(isValid());
+    Q_ASSERT(other.isValid());
+
+    for (const auto key : keys) {
+        const QByteArray groupName = name().toLocal8Bit();
+        const auto entry = config()->d_ptr->lookupInternalEntry(groupName, key, KEntryMap::SearchLocalized);
+
+        // Only write the entry if it is not null, if it is a global enry there is no point in moving it
+        if (!entry.mValue.isNull() && !entry.bGlobal) {
+            deleteEntry(key, pFlags);
+            KEntryMap::EntryOptions options = KEntryMap::EntryOption::EntryDirty;
+            if (entry.bDeleted) {
+                options |= KEntryMap::EntryDeleted;
+            }
+
+            if (entry.bExpand) {
+                options |= KEntryMap::EntryExpansion;
+            }
+
+            other.config()->d_ptr->setEntryData(other.name().toLocal8Bit(), key, entry.mValue, options);
+        }
+    }
+}
diff --git a/src/core/kconfiggroup.h b/src/core/kconfiggroup.h
index 2584cb85..8a6243af 100644
--- a/src/core/kconfiggroup.h
+++ b/src/core/kconfiggroup.h
@@ -195,6 +195,14 @@ public:
     void reparent(KConfigBase *parent, WriteConfigFlags pFlags = Normal);
 
     /**
+     * Moves the key-value pairs from one config group to the other.
+     * In case the entries do not exist the key is ignored.
+     *
+     * @since 5.88
+     */
+    void moveValuesTo(const QList<const char *> &keys, KConfigGroup &other, WriteConfigFlags pFlags = Normal);
+
+    /**
      * Returns the group that this group belongs to
      *
      * @return the parent group, or an invalid group if this is a top-level