Pass "this" object when evaluating debug jobs

We have to explicitly specify the "this" object on QV4::Function::call,
otherwise it will assume undefined or the QML global object.

Task-number: QTBUG-66942
Change-Id: I1af7742b4fee1b49e9760a413834daf3edb15d74
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

5 files changed, 53 insertions, 8 deletions

diff --git a/src/plugins/qmltooling/qmldbg_debugger/qv4debugjob.cpp b/src/plugins/qmltooling/qmldbg_debugger/qv4debugjob.cpp
index 5b049ab521..7950d21612 100644
--- a/src/plugins/qmltooling/qmldbg_debugger/qv4debugjob.cpp
+++ b/src/plugins/qmltooling/qmldbg_debugger/qv4debugjob.cpp
@@ -112,8 +112,14 @@ void JavaScriptJob::run()
     script.inheritContext = true;
     script.parse();
     QV4::ScopedValue result(scope);
-    if (!scope.engine->hasException)
-        result = script.run();
+    if (!scope.engine->hasException) {
+        if (frame) {
+            QV4::ScopedValue thisObject(scope, frame->thisObject());
+            result = script.run(thisObject);
+        } else {
+            result = script.run();
+        }
+    }
     if (scope.engine->hasException) {
         result = scope.engine->catchException();
         resultIsException = true;
diff --git a/src/plugins/qmltooling/qmldbg_nativedebugger/qqmlnativedebugservice.cpp b/src/plugins/qmltooling/qmldbg_nativedebugger/qqmlnativedebugservice.cpp
index 718975275a..e17fe92983 100644
--- a/src/plugins/qmltooling/qmldbg_nativedebugger/qqmlnativedebugservice.cpp
+++ b/src/plugins/qmltooling/qmldbg_nativedebugger/qqmlnativedebugservice.cpp
@@ -260,8 +260,14 @@ QV4::ReturnedValue NativeDebugger::evaluateExpression(const QString &expression)
     // That is a side-effect of inheritContext.
     script.inheritContext = true;
     script.parse();
-    if (!m_engine->hasException)
-        return script.run();
+    if (!m_engine->hasException) {
+        if (m_engine->currentStackFrame) {
+            QV4::ScopedValue thisObject(scope, m_engine->currentStackFrame->thisObject());
+            script.run(thisObject);
+        } else {
+            script.run();
+        }
+    }
 
     m_runningJob = false;
     return QV4::Encode::undefined();
diff --git a/src/qml/jsruntime/qv4script.cpp b/src/qml/jsruntime/qv4script.cpp
index bb6608bec0..267c93952d 100644
--- a/src/qml/jsruntime/qv4script.cpp
+++ b/src/qml/jsruntime/qv4script.cpp
@@ -136,7 +136,7 @@ void Script::parse()
     }
 }
 
-ReturnedValue Script::run()
+ReturnedValue Script::run(const QV4::Value *thisObject)
 {
     if (!parsed)
         parse();
@@ -149,10 +149,11 @@ ReturnedValue Script::run()
     if (qmlContext.isUndefined()) {
         TemporaryAssignment<Function*> savedGlobalCode(engine->globalCode, vmFunction);
 
-        return vmFunction->call(engine->globalObject, nullptr, 0, context);
+        return vmFunction->call(thisObject ? thisObject : engine->globalObject, nullptr, 0,
+                                context);
     } else {
         Scoped<QmlContext> qml(valueScope, qmlContext.value());
-        return vmFunction->call(nullptr, nullptr, 0, qml);
+        return vmFunction->call(thisObject, nullptr, 0, qml);
     }
 }
 
diff --git a/src/qml/jsruntime/qv4script_p.h b/src/qml/jsruntime/qv4script_p.h
index 24291b9aa6..cb03c6b064 100644
--- a/src/qml/jsruntime/qv4script_p.h
+++ b/src/qml/jsruntime/qv4script_p.h
@@ -93,7 +93,7 @@ struct Q_QML_EXPORT Script {
     bool parseAsBinding;
 
     void parse();
-    ReturnedValue run();
+    ReturnedValue run(const QV4::Value *thisObject = nullptr);
 
     Function *function();
 
diff --git a/tests/auto/qml/debugger/qv4debugger/tst_qv4debugger.cpp b/tests/auto/qml/debugger/qv4debugger/tst_qv4debugger.cpp
index 5dd62da15a..4ce0f9fd89 100644
--- a/tests/auto/qml/debugger/qv4debugger/tst_qv4debugger.cpp
+++ b/tests/auto/qml/debugger/qv4debugger/tst_qv4debugger.cpp
@@ -316,6 +316,8 @@ private slots:
 
     void lastLineOfConditional_data();
     void lastLineOfConditional();
+
+    void readThis();
 private:
     QV4Debugger *debugger() const
     {
@@ -865,6 +867,36 @@ void tst_qv4debugger::lastLineOfConditional()
     QCOMPARE(secondState.lineNumber, lastLine);
 }
 
+void tst_qv4debugger::readThis()
+{
+    m_debuggerAgent->m_captureContextInfo = true;
+    QString script =
+            "var x = function() {\n"
+            "    return this.a;\n"
+            "}.apply({a : 5}, []);\n";
+
+    TestAgent::ExpressionRequest request;
+    request.expression = "this";
+    request.frameNr = 0;
+    request.context = -1; // no extra context
+    m_debuggerAgent->m_expressionRequests << request;
+
+    debugger()->addBreakPoint("applyThis", 2);
+    evaluateJavaScript(script, "applyThis");
+    QVERIFY(m_debuggerAgent->m_wasPaused);
+
+    QCOMPARE(m_debuggerAgent->m_expressionResults.count(), 1);
+    QJsonObject result0 = m_debuggerAgent->m_expressionResults[0];
+    QCOMPARE(result0.value("type").toString(), QStringLiteral("object"));
+    QCOMPARE(result0.value("value").toInt(), 1);
+    QJsonArray properties = result0.value("properties").toArray();
+    QCOMPARE(properties.size(), 1);
+    QJsonObject a = properties.first().toObject();
+    QCOMPARE(a.value("name").toString(), QStringLiteral("a"));
+    QCOMPARE(a.value("type").toString(), QStringLiteral("number"));
+    QCOMPARE(a.value("value").toInt(), 5);
+}
+
 void tst_qv4debugger::redundancy_data()
 {
     QTest::addColumn<bool>("redundantRefs");