Make WASM IDB settings use the fallback mechanism correctly

Change-Id: Ibb65efc0faa5ec6e6c60782747c9295e4fc5ff21
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

src/corelib/io/qsettings_p.h

@@ -243,6 +243,9 @@ public:
                             qsizetype &lineStart, qsizetype &lineLen,
                             qsizetype &equalsPos);
 
+protected:
+    const QList<QConfFile *> &getConfFiles() const { return confFiles; }
+
 private:
     void initFormat();
     virtual void initAccess();

src/corelib/io/qsettings_wasm.cpp

@@ -238,10 +238,11 @@ public:
 
     void clear() override;
     void sync() override;
-    void flush() override;
 
 private:
     bool writeSettingsToTemporaryFile(const QString &fileName, void *dataPtr, int size);
+    void loadIndexedDBFiles();
+
 
     QString databaseName;
     QString id;
@@ -264,22 +265,7 @@ QWasmIDBSettingsPrivate::QWasmIDBSettingsPrivate(QSettings::Scope scope,
     databaseName = organization;
     id = application;
 
-    int exists = 0;
-    int error = 0;
-    emscripten_idb_exists(DbName, fileName().toLocal8Bit(), &exists, &error);
-    if (error) {
-        setStatus(QSettings::AccessError);
-        return;
-    }
-    if (exists) {
-        void *contents;
-        int size;
-        emscripten_idb_load(DbName, fileName().toLocal8Bit(), &contents, &size, &error);
-        if (error || !writeSettingsToTemporaryFile(fileName(), contents, size)) {
-            setStatus(QSettings::AccessError);
-            return;
-        }
-    }
+    loadIndexedDBFiles();
 
     QConfFileSettingsPrivate::initAccess();
 }
@@ -288,7 +274,6 @@ QWasmIDBSettingsPrivate::~QWasmIDBSettingsPrivate() = default;
 
 bool QWasmIDBSettingsPrivate::writeSettingsToTemporaryFile(const QString &fileName, void *dataPtr,
                                                            int size)
-
 {
     QFile file(fileName);
     QFileInfo fileInfo(fileName);
@@ -313,6 +298,10 @@ void QWasmIDBSettingsPrivate::clear()
 
 void QWasmIDBSettingsPrivate::sync()
 {
+    // Reload the files, in case there were any changes in IndexedDB, and flush them to disk.
+    // Thanks to this, QConfFileSettingsPrivate::sync will handle key merging correctly.
+    loadIndexedDBFiles();
+
     QConfFileSettingsPrivate::sync();
 
     QFile file(fileName());
@@ -327,9 +316,26 @@ void QWasmIDBSettingsPrivate::sync()
     }
 }
 
-void QWasmIDBSettingsPrivate::flush()
+void QWasmIDBSettingsPrivate::loadIndexedDBFiles()
 {
-    sync();
+    for (const auto *confFile : getConfFiles()) {
+        int exists = 0;
+        int error = 0;
+        emscripten_idb_exists(DbName, confFile->name.toLocal8Bit(), &exists, &error);
+        if (error) {
+            setStatus(QSettings::AccessError);
+            return;
+        }
+        if (exists) {
+            void *contents;
+            int size;
+            emscripten_idb_load(DbName, confFile->name.toLocal8Bit(), &contents, &size, &error);
+            if (error || !writeSettingsToTemporaryFile(confFile->name, contents, size)) {
+                setStatus(QSettings::AccessError);
+                return;
+            }
+        }
+    }
 }
 
 QSettingsPrivate *QSettingsPrivate::create(QSettings::Format format, QSettings::Scope scope,

tests/auto/corelib/io/qsettings/tst_qsettings.cpp

@@ -2058,6 +2058,14 @@ void tst_QSettings::testChildKeysAndGroups()
         l.sort();
         QCOMPARE(l, QStringList() << "bar" << "foo");
     }
+
+#if defined(Q_OS_WASM)
+    // WebIndexedDBFormat does not use the cached settings file on creation, but instead always uses
+    // the file from the indexed DB anew.
+    if (format == QSettings::Format::WebIndexedDBFormat)
+        settings1.sync();
+#endif
+
     {
         QSettings settings3(format, QSettings::UserScope, "software.org", "application");
         settings3.setFallbacksEnabled(false);
@@ -3542,6 +3550,8 @@ void tst_QSettings::rainersSyncBugOnMac()
 #if defined(Q_OS_WASM)
     if (format == QSettings::NativeFormat)
         QSKIP("WASM's localStorage backend recognizes no concept of file");
+    if (format == QSettings::WebIndexedDBFormat)
+        QSKIP("WASM's indexedDB backend uses the virtual FS file only as a backing store");
 #endif  // Q_OS_WASM
 
     QString fileName;