Fix QtScript debugger hang/crash issue with updating locals model

Since the model is updated lazily, it's possible that a new model
has been set on the view (and the old model deleted) before the old
model has finished refreshing. This was discovered while holding
down the F11 key (Step Into) when debugging plasma.js in the
script/context2d example, which causes many events (and hence
asynchronous model updates) to trigger rapidly.

2 files changed, 44 insertions, 16 deletions

diff --git a/src/scripttools/debugging/qscriptdebuggerlocalsmodel.cpp b/src/scripttools/debugging/qscriptdebuggerlocalsmodel.cpp
index 068de42b57..ec6230bc9e 100644
--- a/src/scripttools/debugging/qscriptdebuggerlocalsmodel.cpp
+++ b/src/scripttools/debugging/qscriptdebuggerlocalsmodel.cpp
@@ -54,6 +54,7 @@
 
 #include <QtCore/qdebug.h>
 #include <QtCore/qcoreapplication.h>
+#include <QtCore/qpointer.h>
 #include <QtGui/qbrush.h>
 #include <QtGui/qfont.h>
 
@@ -370,6 +371,7 @@ public:
     {
         if (!m_index.isValid()) {
             // nothing to do, the node has been removed
+            finish();
             return;
         }
         QScriptDebuggerCommandSchedulerFrontend frontend(commandScheduler(), this);
@@ -475,7 +477,7 @@ namespace {
 class InitModelJob : public QScriptDebuggerCommandSchedulerJob
 {
 public:
-    InitModelJob(QScriptDebuggerLocalsModelPrivate *model,
+    InitModelJob(QScriptDebuggerLocalsModel *model,
                  int frameIndex,
                  QScriptDebuggerCommandSchedulerInterface *scheduler)
         : QScriptDebuggerCommandSchedulerJob(scheduler),
@@ -484,6 +486,11 @@ public:
 
     void start()
     {
+        if (!m_model) {
+            // Model has been deleted.
+            finish();
+            return;
+        }
         QScriptDebuggerCommandSchedulerFrontend frontend(commandScheduler(), this);
         frontend.scheduleGetScopeChain(m_frameIndex);
     }
@@ -491,7 +498,13 @@ public:
     void handleResponse(const QScriptDebuggerResponse &response,
                         int)
     {
+        if (!m_model) {
+            // Model has been deleted.
+            finish();
+            return;
+        }
         QScriptDebuggerCommandSchedulerFrontend frontend(commandScheduler(), this);
+        QScriptDebuggerLocalsModelPrivate *model_d = QScriptDebuggerLocalsModelPrivate::get(m_model);
         switch (m_state) {
         case 0: {
             QScriptDebuggerValueList scopeChain = response.resultAsScriptValueList();
@@ -500,23 +513,23 @@ public:
                 QString name = QString::fromLatin1("Scope");
                 if (i > 0)
                     name.append(QString::fromLatin1(" (%0)").arg(i));
-                QModelIndex index = m_model->addTopLevelObject(name, scopeObject);
+                QModelIndex index = model_d->addTopLevelObject(name, scopeObject);
                 if (i == 0)
-                    m_model->emitScopeObjectAvailable(index);
+                    model_d->emitScopeObjectAvailable(index);
             }
             frontend.scheduleGetThisObject(m_frameIndex);
             ++m_state;
         }   break;
         case 1: {
             QScriptDebuggerValue thisObject = response.resultAsScriptValue();
-            m_model->addTopLevelObject(QLatin1String("this"), thisObject);
+            model_d->addTopLevelObject(QLatin1String("this"), thisObject);
             finish();
           } break;
         }
     }
 
 private:
-    QScriptDebuggerLocalsModelPrivate *m_model;
+    QPointer<QScriptDebuggerLocalsModel> m_model;
     int m_frameIndex;
     int m_state;
 };
@@ -527,7 +540,7 @@ void QScriptDebuggerLocalsModel::init(int frameIndex)
 {
     Q_D(QScriptDebuggerLocalsModel);
     d->frameIndex = frameIndex;
-    QScriptDebuggerJob *job = new InitModelJob(d, frameIndex, d->commandScheduler);
+    QScriptDebuggerJob *job = new InitModelJob(this, frameIndex, d->commandScheduler);
     d->jobScheduler->scheduleJob(job);
 }
 
@@ -536,7 +549,7 @@ namespace {
 class SyncModelJob : public QScriptDebuggerCommandSchedulerJob
 {
 public:
-    SyncModelJob(QScriptDebuggerLocalsModelPrivate *model,
+    SyncModelJob(QScriptDebuggerLocalsModel *model,
                  int frameIndex,
                  QScriptDebuggerCommandSchedulerInterface *scheduler)
         : QScriptDebuggerCommandSchedulerJob(scheduler),
@@ -545,6 +558,11 @@ public:
 
     void start()
     {
+        if (!m_model) {
+            // Model has been deleted.
+            finish();
+            return;
+        }
         QScriptDebuggerCommandSchedulerFrontend frontend(commandScheduler(), this);
         frontend.scheduleGetScopeChain(m_frameIndex);
     }
@@ -552,6 +570,11 @@ public:
     void handleResponse(const QScriptDebuggerResponse &response,
                         int)
     {
+        if (!m_model) {
+            // Model has been deleted.
+            finish();
+            return;
+        }
         QScriptDebuggerCommandSchedulerFrontend frontend(commandScheduler(), this);
         switch (m_state) {
         case 0: {
@@ -561,18 +584,19 @@ public:
             ++m_state;
         }   break;
         case 1: {
+            QScriptDebuggerLocalsModelPrivate *model_d = QScriptDebuggerLocalsModelPrivate::get(m_model);
             QScriptDebuggerValue thisObject = response.resultAsScriptValue();
             m_topLevelObjects.append(thisObject);
-            bool equal = (m_topLevelObjects.size() == m_model->invisibleRootNode->children.size());
+            bool equal = (m_topLevelObjects.size() == model_d->invisibleRootNode->children.size());
             for (int i = 0; equal && (i < m_topLevelObjects.size()); ++i) {
                 const QScriptDebuggerValue &object = m_topLevelObjects.at(i);
-                equal = (object == m_model->invisibleRootNode->children.at(i)->property.value());
+                equal = (object == model_d->invisibleRootNode->children.at(i)->property.value());
             }
             if (!equal) {
                 // the scope chain and/or this-object changed, so invalidate the model.
                 // we could try to be more clever, i.e. figure out
                 // exactly which objects were popped/pushed
-                m_model->removeTopLevelNodes();
+                model_d->removeTopLevelNodes();
                 for (int j = 0; j < m_topLevelObjects.size(); ++j) {
                     const QScriptDebuggerValue &object = m_topLevelObjects.at(j);
                     QString name;
@@ -583,12 +607,12 @@ public:
                         if (j > 0)
                             name.append(QString::fromLatin1(" (%0)").arg(j));
                     }
-                    QModelIndex index = m_model->addTopLevelObject(name, object);
+                    QModelIndex index = model_d->addTopLevelObject(name, object);
                     if (j == 0)
-                        m_model->emitScopeObjectAvailable(index);
+                        model_d->emitScopeObjectAvailable(index);
                 }
             } else {
-                m_model->syncTopLevelNodes();
+                model_d->syncTopLevelNodes();
             }
             finish();
           } break;
@@ -596,7 +620,7 @@ public:
     }
 
 private:
-    QScriptDebuggerLocalsModelPrivate *m_model;
+    QPointer<QScriptDebuggerLocalsModel> m_model;
     int m_frameIndex;
     int m_state;
     QScriptDebuggerValueList m_topLevelObjects;
@@ -608,7 +632,7 @@ void QScriptDebuggerLocalsModel::sync(int frameIndex)
 {
     Q_D(QScriptDebuggerLocalsModel);
     d->frameIndex = frameIndex;
-    QScriptDebuggerJob *job = new SyncModelJob(d, frameIndex, d->commandScheduler);
+    QScriptDebuggerJob *job = new SyncModelJob(this, frameIndex, d->commandScheduler);
     d->jobScheduler->scheduleJob(job);
 }
 
@@ -636,6 +660,7 @@ public:
     {
         if (!m_index.isValid()) {
             // nothing to do, the node has been removed
+            finish();
             return;
         }
         QScriptDebuggerCommandSchedulerFrontend frontend(commandScheduler(), this);
diff --git a/src/scripttools/debugging/qscriptdebuggerlocalswidget.cpp b/src/scripttools/debugging/qscriptdebuggerlocalswidget.cpp
index 516a200637..bbced5ff90 100644
--- a/src/scripttools/debugging/qscriptdebuggerlocalswidget.cpp
+++ b/src/scripttools/debugging/qscriptdebuggerlocalswidget.cpp
@@ -70,6 +70,8 @@ public:
 
     bool hasChildren(const QModelIndex &parent) const
     {
+        if (!sourceModel())
+            return false;
         QModelIndex sourceParent = mapToSource(parent);
         if (parent.isValid() && !sourceParent.isValid())
             return false;
@@ -184,7 +186,8 @@ void QScriptDebuggerLocalsWidgetPrivate::_q_insertCompletion(const QString &text
 
 void QScriptDebuggerLocalsWidgetPrivate::_q_expandIndex(const QModelIndex &index)
 {
-    view->expand(proxy->mapFromSource(index));
+    if (view->model() == index.model())
+        view->expand(proxy->mapFromSource(index));
 }
 
 class QScriptDebuggerLocalsItemDelegate