reset debugger's state correctly when previous engine was deleted

If the engine was deleted, the agent will be 0, but we still
want to fall through rather than return immediately, so that
the other variables are reset correctly.

2 files changed, 23 insertions, 15 deletions

diff --git a/src/scripttools/debugging/qscriptdebuggerbackend.cpp b/src/scripttools/debugging/qscriptdebuggerbackend.cpp
index 9eaf571..da9d50e 100644
--- a/src/scripttools/debugging/qscriptdebuggerbackend.cpp
+++ b/src/scripttools/debugging/qscriptdebuggerbackend.cpp
@@ -433,21 +433,21 @@ void QScriptDebuggerBackend::attachTo(QScriptEngine *engine)
 void QScriptDebuggerBackend::detach()
 {
     Q_D(QScriptDebuggerBackend);
-    if (!d->agent)
-        return;
-    QScriptEngine *eng = d->agent->engine();
-    if (eng && eng->agent() == d->agent) {
-        eng->setAgent(0);
-        QScriptValue global = eng->globalObject();
-        if (global.property(QString::fromLatin1("print")).strictlyEquals(traceFunction()))
-            global.setProperty(QString::fromLatin1("print"), QScriptValue());
-//        global.setProperty(QString::fromLatin1("qAssert"), QScriptValue());
-        if (global.property(QString::fromLatin1("__FILE__")).strictlyEquals(fileNameFunction()))
-            global.setProperty(QString::fromLatin1("__FILE__"), QScriptValue());
-        if (global.property(QString::fromLatin1("__LINE__")).strictlyEquals(lineNumberFunction()))
-            global.setProperty(QString::fromLatin1("__LINE__"), QScriptValue());
-        d->agent->nullifyBackendPointer();
-        d->agent = 0; // agent is owned by engine
+    if (d->agent) {
+        QScriptEngine *eng = d->agent->engine();
+        if (eng && eng->agent() == d->agent) {
+            eng->setAgent(0);
+            QScriptValue global = eng->globalObject();
+            if (global.property(QString::fromLatin1("print")).strictlyEquals(traceFunction()))
+                global.setProperty(QString::fromLatin1("print"), QScriptValue());
+//            global.setProperty(QString::fromLatin1("qAssert"), QScriptValue());
+            if (global.property(QString::fromLatin1("__FILE__")).strictlyEquals(fileNameFunction()))
+                global.setProperty(QString::fromLatin1("__FILE__"), QScriptValue());
+            if (global.property(QString::fromLatin1("__LINE__")).strictlyEquals(lineNumberFunction()))
+                global.setProperty(QString::fromLatin1("__LINE__"), QScriptValue());
+            d->agent->nullifyBackendPointer();
+            d->agent = 0; // agent is owned by engine
+        }
     }
 
     d->pendingEvaluateLineNumber = -1;
diff --git a/tests/auto/qscriptenginedebugger/tst_qscriptenginedebugger.cpp b/tests/auto/qscriptenginedebugger/tst_qscriptenginedebugger.cpp
index 7f3f9f3..5e5b701 100644
--- a/tests/auto/qscriptenginedebugger/tst_qscriptenginedebugger.cpp
+++ b/tests/auto/qscriptenginedebugger/tst_qscriptenginedebugger.cpp
@@ -163,6 +163,14 @@ void tst_QScriptEngineDebugger::attachAndDetach()
         debugger2.attachTo(&engine);
     }
 #endif
+    {
+        QScriptEngine *engine = new QScriptEngine;
+        QScriptEngineDebugger debugger;
+        debugger.attachTo(engine);
+        delete engine;
+        QScriptEngine engine2;
+        debugger.attachTo(&engine2);
+    }
 }
 
 void tst_QScriptEngineDebugger::action()