V4 Debugger: If no context is given inject the QML context

The user generally expects QML "root" objects to be in a "global"
scope. Or at least that makes debugging a lot easier. By opening a
WithContext with the relevant objects we can simulate that.

Task-number: QTCREATORBUG-14931
Change-Id: I89af0560803b2c54a35f08e9fd659e65fb937cb9
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>

3 files changed, 55 insertions, 9 deletions

diff --git a/src/plugins/qmltooling/qmldbg_debugger/qv4datacollector.cpp b/src/plugins/qmltooling/qmldbg_debugger/qv4datacollector.cpp
index ac46905f1c..78cb2be8d3 100644
--- a/src/plugins/qmltooling/qmldbg_debugger/qv4datacollector.cpp
+++ b/src/plugins/qmltooling/qmldbg_debugger/qv4datacollector.cpp
@@ -39,6 +39,9 @@
 #include <private/qv4identifier_p.h>
 #include <private/qv4runtime_p.h>
 
+#include <private/qqmlcontext_p.h>
+#include <private/qqmlengine_p.h>
+
 #include <QtCore/qjsonarray.h>
 #include <QtCore/qjsonobject.h>
 
@@ -352,6 +355,17 @@ QJsonObject QV4DataCollector::collectAsJson(const QString &name, const QV4::Scop
 
 void ValueLookupJob::run()
 {
+    // Open a QML context if we don't have one, yet. We might run into QML objects when looking up
+    // refs and that will crash without a valid QML context. Mind that engine->qmlContext() is only
+    // set if the engine is currently executing QML code.
+    QScopedPointer<QObject> scopeObject;
+    QV4::ExecutionEngine *engine = collector->engine();
+    if (engine->qmlEngine() && !engine->qmlContext()) {
+        scopeObject.reset(new QObject);
+        engine->pushContext(engine->currentContext->newQmlContext(
+                                QQmlContextData::get(engine->qmlEngine()->rootContext()),
+                                scopeObject.data()));
+    }
     foreach (const QJsonValue &handle, handles) {
         QV4DataCollector::Ref ref = handle.toInt();
         if (!collector->isValidRef(ref)) {
@@ -361,6 +375,8 @@ void ValueLookupJob::run()
         result[QString::number(ref)] = collector->lookupRef(ref);
     }
     collectedRefs = collector->flushCollectedRefs();
+    if (scopeObject)
+        engine->popContext();
 }
 
 const QString &ValueLookupJob::exceptionMessage() const
diff --git a/src/plugins/qmltooling/qmldbg_debugger/qv4debugger.cpp b/src/plugins/qmltooling/qmldbg_debugger/qv4debugger.cpp
index a7ef1ede6b..b7c310edd8 100644
--- a/src/plugins/qmltooling/qmldbg_debugger/qv4debugger.cpp
+++ b/src/plugins/qmltooling/qmldbg_debugger/qv4debugger.cpp
@@ -36,6 +36,8 @@
 
 #include <private/qv4scopedvalue_p.h>
 #include <private/qv4script_p.h>
+#include <private/qqmlcontext_p.h>
+#include <private/qqmlengine_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -69,11 +71,38 @@ void QV4Debugger::JavaScriptJob::run()
     QV4::ExecutionContextSaver saver(scope);
 
     QV4::ExecutionContext *ctx = engine->currentContext;
-    if (frameNr > 0) {
-        for (int i = 0; i < frameNr; ++i) {
-            ctx = engine->parentContext(ctx);
+    QObject scopeObject;
+    if (frameNr < 0) { // Use QML context if available
+        QQmlEngine *qmlEngine = engine->qmlEngine();
+        if (qmlEngine) {
+            QQmlContext *qmlRootContext = qmlEngine->rootContext();
+            QQmlContextPrivate *ctxtPriv = QQmlContextPrivate::get(qmlRootContext);
+
+            QV4::ScopedObject withContext(scope, engine->newObject());
+            for (int ii = 0; ii < ctxtPriv->instances.count(); ++ii) {
+                QObject *object = ctxtPriv->instances.at(ii);
+                if (QQmlContext *context = qmlContext(object)) {
+                    if (QQmlContextData *cdata = QQmlContextData::get(context)) {
+                        QV4::ScopedValue v(scope, QV4::QObjectWrapper::wrap(engine, object));
+                        withContext->put(engine, cdata->findObjectId(object), v);
+                    }
+                }
+            }
+            if (!engine->qmlContext()) {
+                engine->pushContext(ctx->newQmlContext(QQmlContextData::get(qmlRootContext),
+                                                       &scopeObject));
+                ctx = engine->currentContext;
+            }
+            engine->pushContext(ctx->newWithContext(withContext->toObject(engine)));
+            ctx = engine->currentContext;
+        }
+    } else {
+        if (frameNr > 0) {
+            for (int i = 0; i < frameNr; ++i) {
+                ctx = engine->parentContext(ctx);
+            }
+            engine->pushContext(ctx);
         }
-        engine->pushContext(ctx);
     }
 
     QV4::Script script(ctx, this->script);
diff --git a/src/plugins/qmltooling/qmldbg_debugger/qv4debugservice.cpp b/src/plugins/qmltooling/qmldbg_debugger/qv4debugservice.cpp
index 6524a1ff28..dcf1fe8335 100644
--- a/src/plugins/qmltooling/qmldbg_debugger/qv4debugservice.cpp
+++ b/src/plugins/qmltooling/qmldbg_debugger/qv4debugservice.cpp
@@ -602,8 +602,11 @@ public:
 
     virtual void handleRequest()
     {
-        QV4Debugger *debugger = debugService->debuggerAgent.pausedDebugger();
+        QJsonObject arguments = req.value(QStringLiteral("arguments")).toObject();
+        QString expression = arguments.value(QStringLiteral("expression")).toString();
+        int frame = -1;
 
+        QV4Debugger *debugger = debugService->debuggerAgent.pausedDebugger();
         if (!debugger) {
             const QList<QV4Debugger *> &debuggers = debugService->debuggerAgent.debuggers();
             if (debuggers.count() > 1) {
@@ -614,12 +617,10 @@ public:
                 return;
             }
             debugger = debuggers.first();
+        } else {
+            frame = arguments.value(QStringLiteral("frame")).toInt(0);
         }
 
-        QJsonObject arguments = req.value(QStringLiteral("arguments")).toObject();
-        QString expression = arguments.value(QStringLiteral("expression")).toString();
-        const int frame = arguments.value(QStringLiteral("frame")).toInt(0);
-
         ExpressionEvalJob job(debugger->engine(), frame, expression, debugger->collector());
         debugger->runInEngine(&job);
         if (job.hasExeption()) {