Add QJSEngine::registerModule

Some applications that use JavaScript as a scripting language may want
to extend JS through C++ code. The current way to do that is with
global objects.
ES6 provides a better way of encapsulating code: modules.
registerModule() allows an application to provide a QJSValue as a named module.
Developers familiar with Node.js will find this very easy to use.

Example:
```c++
QJSValue num(666);
myEngine.registerModule("themarkofthebeast", num);
```
```js
import badnews from "themarkofthebeast";
```

[ChangeLog][QtQml][QJSEngine] Adds the ability to register QJSValues in
C++ as modules for importing in MJS files.

Change-Id: I0c98dcb746aa2aa15aa2ab3082129d106413a23b
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/qml/jsruntime/qv4engine_p.h b/src/qml/jsruntime/qv4engine_p.h
index e3e0a481cf..fe31b42c84 100644
--- a/src/qml/jsruntime/qv4engine_p.h
+++ b/src/qml/jsruntime/qv4engine_p.h
@@ -760,9 +760,17 @@ public:
 
     mutable QMutex moduleMutex;
     QHash<QUrl, QQmlRefPointer<ExecutableCompilationUnit>> modules;
+
+    // QV4::PersistentValue would be preferred, but using QHash will create copies,
+    // and QV4::PersistentValue doesn't like creating copies.
+    // Instead, we allocate a raw pointer using the same manual memory management
+    // technique in QV4::PersistentValue.
+    QHash<QUrl, QV4::Value*> nativeModules;
+
     void injectModule(const QQmlRefPointer<ExecutableCompilationUnit> &moduleUnit);
     QQmlRefPointer<ExecutableCompilationUnit> moduleForUrl(const QUrl &_url, const ExecutableCompilationUnit *referrer = nullptr) const;
     QQmlRefPointer<ExecutableCompilationUnit> loadModule(const QUrl &_url, const ExecutableCompilationUnit *referrer = nullptr);
+    void registerModule(const QString &name, const QJSValue &module);
 
     bool diskCacheEnabled() const;