Fix IPyKernel restarting

src/python/cutter_ipykernel.py

@@ -3,6 +3,7 @@ import logging
 import threading
 import signal
 import cutter_internal
+import zmq
 from ipykernel.kernelapp import IPKernelApp
 from ipykernel.ipkernel import IPythonKernel
 
@@ -28,6 +29,16 @@ class IPyKernelInterfaceKernel:
         else:
             return 0
 
+    def cleanup(self):
+        self._app.heartbeat.context.destroy()
+        self._thread.join()
+        self._app.heartbeat.join()
+        self._app.iopub_thread.stop()
+        self._app.kernel.shell.history_manager.save_thread.stop()
+        zmq.Context.instance().destroy()
+        # successful if only the main thread remains
+        return len(threading.enumerate()) == 1
+
 
 class CutterIPythonKernel(IPythonKernel):
     def __init__(self, **kwargs):

src/utils/JupyterConnection.cpp

@@ -156,3 +156,29 @@ NestedIPyKernel *JupyterConnection::getNestedIPyKernel(long id)
     }
     return *it;
 }
+
+QVariant JupyterConnection::pollNestedIPyKernel(long id)
+{
+    auto it = kernels.find(id);
+    if(it == kernels.end())
+    {
+        return QVariant(0);
+    }
+
+    NestedIPyKernel *kernel = *it;
+    QVariant v = kernel->poll();
+
+    if(!v.isNull())
+    {
+        // if poll of kernel returns anything but None, it has already quit and should be cleaned up
+        PyThreadState *subinterpreterState = kernel->getThreadState();
+        delete kernel;
+        kernels.erase(it);
+
+        PyThreadState *parentThreadState = PyThreadState_Swap(subinterpreterState);
+        Py_EndInterpreter(subinterpreterState);
+        PyThreadState_Swap(parentThreadState);
+    }
+
+    return v;
+}

src/utils/JupyterConnection.h

@@ -26,6 +26,7 @@ public:
 
     long startNestedIPyKernel(const QStringList &argv);
     NestedIPyKernel *getNestedIPyKernel(long id);
+    QVariant pollNestedIPyKernel(long id);
 
 signals:
     void urlReceived(const QString &url);

src/utils/NestedIPyKernel.cpp

@@ -62,6 +62,13 @@ NestedIPyKernel::NestedIPyKernel(PyObject *cutterIPykernelModule, const QStringL
 
 NestedIPyKernel::~NestedIPyKernel()
 {
+    auto parentThreadState = PyThreadState_Swap(threadState);
+    auto ret = PyObject_CallMethod(kernel, "cleanup", nullptr);
+    if (!ret)
+    {
+        PyErr_Print();
+    }
+    PyThreadState_Swap(parentThreadState);
 }
 
 void NestedIPyKernel::sendSignal(long signum)

src/utils/NestedIPyKernel.h

@@ -20,6 +20,8 @@ public:
     void sendSignal(long signum);
     QVariant poll();
 
+    PyThreadState *getThreadState()     { return threadState; }
+
 private:
     NestedIPyKernel(PyObject *cutterIPykernelModule, const QStringList &argv);
 

src/utils/PythonAPI.cpp

@@ -110,13 +110,7 @@ PyObject *api_internal_kernel_interface_poll(PyObject *, PyObject *args)
         return nullptr;
     }
 
-    NestedIPyKernel *kernel = Jupyter()->getNestedIPyKernel(id);
+    QVariant v = Jupyter()->pollNestedIPyKernel(id);
-    if(!kernel)
-    {
-        return PyLong_FromLong(0);
-    }
-
-    QVariant v = kernel->poll();
     bool ok;
     auto ret = static_cast<long>(v.toLongLong(&ok));
     if(ok)