V4 Debugger: Properly set up context object for expressions

We need to use the object in question as context object in order to
access its properties. Otherwise we can only access the context
properties and, incidentally, the root scope's properties. The latter is
why the test didn't fail.

Fixes: QTBUG-82150
Change-Id: I1f18f9e78dd61786310fd75e0695929522a4c90c
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

3 files changed, 18 insertions, 4 deletions

diff --git a/src/plugins/qmltooling/qmldbg_debugger/qv4debugjob.cpp b/src/plugins/qmltooling/qmldbg_debugger/qv4debugjob.cpp
index 61fea96e2f..333ce4b26f 100644
--- a/src/plugins/qmltooling/qmldbg_debugger/qv4debugjob.cpp
+++ b/src/plugins/qmltooling/qmldbg_debugger/qv4debugjob.cpp
@@ -66,7 +66,6 @@ void JavaScriptJob::run()
 
     QV4::ScopedContext ctx(scope, engine->currentStackFrame ? engine->currentContext()
                                                             : engine->scriptContext());
-    QObject scopeObject;
 
     QV4::CppStackFrame *frame = engine->currentStackFrame;
 
@@ -76,9 +75,10 @@ void JavaScriptJob::run()
         ctx = static_cast<QV4::ExecutionContext *>(&frame->jsFrame->context);
 
     if (context >= 0) {
-        QQmlContext *extraContext = qmlContext(QQmlDebugService::objectForId(context));
+        QObject *forId = QQmlDebugService::objectForId(context);
+        QQmlContext *extraContext = qmlContext(forId);
         if (extraContext)
-            ctx = QV4::QmlContext::create(ctx, QQmlContextData::get(extraContext), &scopeObject);
+            ctx = QV4::QmlContext::create(ctx, QQmlContextData::get(extraContext), forId);
     } else if (frameNr < 0) { // Use QML context if available
         QQmlEngine *qmlEngine = engine->qmlEngine();
         if (qmlEngine) {
@@ -99,7 +99,7 @@ void JavaScriptJob::run()
                 }
             }
             if (!engine->qmlContext())
-                ctx = QV4::QmlContext::create(ctx, QQmlContextData::get(qmlRootContext), &scopeObject);
+                ctx = QV4::QmlContext::create(ctx, QQmlContextData::get(qmlRootContext), nullptr);
         }
     }
 
diff --git a/tests/auto/qml/debugger/qqmldebugjs/data/oncompleted.qml b/tests/auto/qml/debugger/qqmldebugjs/data/oncompleted.qml
index deba24cf91..a7231df48b 100644
--- a/tests/auto/qml/debugger/qqmldebugjs/data/oncompleted.qml
+++ b/tests/auto/qml/debugger/qqmldebugjs/data/oncompleted.qml
@@ -36,5 +36,9 @@ Item {
     }
     id: root
     property int a: 10
+
+    Item {
+        property int b: 11
+    }
 }
 
diff --git a/tests/auto/qml/debugger/qqmldebugjs/tst_qqmldebugjs.cpp b/tests/auto/qml/debugger/qqmldebugjs/tst_qqmldebugjs.cpp
index 3f424d16f2..91470e0651 100644
--- a/tests/auto/qml/debugger/qqmldebugjs/tst_qqmldebugjs.cpp
+++ b/tests/auto/qml/debugger/qqmldebugjs/tst_qqmldebugjs.cpp
@@ -896,6 +896,16 @@ void tst_QQmlDebugJS::evaluateInContext()
     QVERIFY(waitForClientSignal(SIGNAL(result())));
 
     QTRY_COMPARE(responseBody(m_client).value("value").toInt(), 20);
+
+    auto childObjects = object.children;
+    QVERIFY(childObjects.count() > 0); // QQmlComponentAttached is also in there
+    QCOMPARE(childObjects[0].className, QString::fromLatin1("Item"));
+
+    // "b" accessible in context of surrounding (child) object
+    m_client->evaluate(QLatin1String("b"), -1, childObjects[0].debugId);
+    QVERIFY(waitForClientSignal(SIGNAL(result())));
+
+    QTRY_COMPARE(responseBody(m_client).value("value").toInt(), 11);
 }
 
 void tst_QQmlDebugJS::getScripts()