Port QSettingsPrivate::get() to std::optional

... instead of a bool return and a QVariant out parameter.

Change-Id: I9d937668ede668075d1de5bb57f61e4c260aaddc
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/io/qsettings.cpp

@@ -1202,7 +1202,7 @@ void QConfFileSettingsPrivate::set(const QString &key, const QVariant &value)
     confFile->addedKeys.insert(theKey, value);
 }
 
-bool QConfFileSettingsPrivate::get(const QString &key, QVariant *value) const
+std::optional<QVariant> QConfFileSettingsPrivate::get(const QString &key) const
 {
     QSettingsKey theKey(key, caseSensitivity);
     ParsedSettingsMap::const_iterator j;
@@ -1222,15 +1222,12 @@ bool QConfFileSettingsPrivate::get(const QString &key, QVariant *value) const
                      && !confFile->removedKeys.contains(theKey));
         }
 
-        if (found && value)
-            *value = *j;
-
         if (found)
-            return true;
+            return *j;
         if (!fallbacks)
             break;
     }
-    return false;
+    return std::nullopt;
 }
 
 QStringList QConfFileSettingsPrivate::children(const QString &prefix, ChildSpec spec) const
@@ -3213,7 +3210,7 @@ void QSettings::remove(const QString &key)
 bool QSettings::contains(const QString &key) const
 {
     Q_D(const QSettings);
-    return d->get(d->actualKey(key), nullptr);
+    return d->get(d->actualKey(key)) != std::nullopt;
 }
 
 /*!
@@ -3282,9 +3279,7 @@ QVariant QSettings::value(const QString &key, const QVariant &defaultValue) cons
         qWarning("QSettings::value: Empty key passed");
         return QVariant();
     }
-    QVariant result = defaultValue;
+    return d->get(d->actualKey(key)).value_or(defaultValue);
-    d->get(d->actualKey(key), &result);
-    return result;
 }
 
 /*!

src/corelib/io/qsettings_mac.cpp

@@ -332,7 +332,7 @@ public:
 
     void remove(const QString &key) override;
     void set(const QString &key, const QVariant &value) override;
-    bool get(const QString &key, QVariant *value) const override;
+    std::optional<QVariant> get(const QString &key) const override;
     QStringList children(const QString &prefix, ChildSpec spec) const override;
     void clear() override;
     void sync() override;
@@ -448,7 +448,7 @@ void QMacSettingsPrivate::set(const QString &key, const QVariant &value)
                           domains[0].userName, hostName);
 }
 
-bool QMacSettingsPrivate::get(const QString &key, QVariant *value) const
+std::optional<QVariant> QMacSettingsPrivate::get(const QString &key) const
 {
     QCFString k = macKey(key);
     for (int i = 0; i < numDomains; ++i) {
@@ -456,17 +456,14 @@ bool QMacSettingsPrivate::get(const QString &key, QVariant *value) const
             QCFType<CFPropertyListRef> ret =
                     CFPreferencesCopyValue(k, domains[i].applicationOrSuiteId, domains[i].userName,
                                            hostNames[j]);
-            if (ret) {
+            if (ret)
-                if (value)
+                return qtValue(ret);
-                    *value = qtValue(ret);
-                return true;
-            }
         }
 
         if (!fallbacks)
             break;
     }
-    return false;
+    return std::nullopt;
 }
 
 QStringList QMacSettingsPrivate::children(const QString &prefix, ChildSpec spec) const
@@ -536,7 +533,7 @@ bool QMacSettingsPrivate::isWritable() const
 
     that->set(impossibleKey, QVariant());
     that->sync();
-    bool writable = (status == QSettings::NoError) && that->get(impossibleKey, 0);
+    bool writable = (status == QSettings::NoError) && that->get(impossibleKey).has_value();
     that->remove(impossibleKey);
     that->sync();
 

src/corelib/io/qsettings_p.h

@@ -197,7 +197,7 @@ public:
 
     virtual void remove(const QString &key) = 0;
     virtual void set(const QString &key, const QVariant &value) = 0;
-    virtual bool get(const QString &key, QVariant *value) const = 0;
+    virtual std::optional<QVariant> get(const QString &key) const = 0;
 
     enum ChildSpec { AllKeys, ChildKeys, ChildGroups };
     virtual QStringList children(const QString &prefix, ChildSpec spec) const = 0;
@@ -264,7 +264,7 @@ public:
 
     void remove(const QString &key) override;
     void set(const QString &key, const QVariant &value) override;
-    bool get(const QString &key, QVariant *value) const override;
+    std::optional<QVariant> get(const QString &key) const override;
 
     QStringList children(const QString &prefix, ChildSpec spec) const override;
 

src/corelib/io/qsettings_wasm.cpp

@@ -62,7 +62,7 @@ public:
                         const QString &application);
     ~QWasmSettingsPrivate();
 
-    bool get(const QString &key, QVariant *value) const override;
+    std::optional<QVariant> get(const QString &key) const override;
     QStringList children(const QString &prefix, ChildSpec spec) const override;
     void clear() override;
     void sync() override;
@@ -169,12 +169,12 @@ QWasmSettingsPrivate::~QWasmSettingsPrivate()
          QConfFileSettingsPrivate::initAccess();
 }
 
-bool QWasmSettingsPrivate::get(const QString &key, QVariant *value) const
+std::optional<QVariant> QWasmSettingsPrivate::get(const QString &key) const
 {
     if (isReadReady)
-        return QConfFileSettingsPrivate::get(key, value);
+        return QConfFileSettingsPrivate::get(key);
 
-    return false;
+    return std::nullopt;
 }
 
 QStringList QWasmSettingsPrivate::children(const QString &prefix, ChildSpec spec) const

src/corelib/io/qsettings_win.cpp

@@ -387,7 +387,7 @@ public:
 
     void remove(const QString &uKey) override;
     void set(const QString &uKey, const QVariant &value) override;
-    bool get(const QString &uKey, QVariant *value) const override;
+    std::optional<QVariant> get(const QString &uKey) const override;
     QStringList children(const QString &uKey, ChildSpec spec) const override;
     void clear() override;
     void sync() override;
@@ -747,20 +747,22 @@ void QWinSettingsPrivate::set(const QString &uKey, const QVariant &value)
     RegCloseKey(handle);
 }
 
-bool QWinSettingsPrivate::get(const QString &uKey, QVariant *value) const
+std::optional<QVariant> QWinSettingsPrivate::get(const QString &uKey) const
 {
     QString rKey = escapedKey(uKey);
 
+    QVariant value;
+
     for (const RegistryKey &r : regList) {
         HKEY handle = r.handle();
-        if (handle != 0 && readKey(handle, rKey, value))
+        if (handle != 0 && readKey(handle, rKey, &value))
-            return true;
+            return value;
 
         if (!fallbacks)
-            return false;
+            return std::nullopt;
     }
 
-    return false;
+    return std::nullopt;
 }
 
 QStringList QWinSettingsPrivate::children(const QString &uKey, ChildSpec spec) const