Port variable restart fix (#9938)

* Fix variable explorer when restarting a kernel (#9931)

* Make sure to clear variable list on reset

* Add news entry

* Update changelog

* Update changelog

Author: rchiodo

CHANGELOG.md

@@ -47,6 +47,8 @@
 
 ### Fixes
 
+1. Make sure to clear variable list on restart kernel.
+   ([#9740](https://github.com/Microsoft/vscode-python/issues/9740))
 1. Use the autoStart server when available.
    ([#9926](https://github.com/Microsoft/vscode-python/issues/9926))
 1. Removed unnecessary warning when executing cells that use Scrapbook,
@@ -4966,4 +4968,4 @@ the following people who contributed code:
 * Added ability to view global variables, arguments, add and remove break points
 
 ## Version 0.0.3
-* Added support for debugging using PDB
+* Added support for debugging using PDB

src/datascience-ui/interactive-common/redux/reducers/variables.ts

@@ -22,7 +22,7 @@ type VariableReducerFunc<T> = ReducerFunc<IVariableState, IncomingMessageActions
 type VariableReducerArg<T = never | undefined> = ReducerArg<IVariableState, IncomingMessageActions, T>;
 
 function handleRequest(arg: VariableReducerArg<IJupyterVariablesRequest>): IVariableState {
-    const newExecutionCount = arg.payload.executionCount ? arg.payload.executionCount : arg.prevState.currentExecutionCount;
+    const newExecutionCount = arg.payload.executionCount !== undefined ? arg.payload.executionCount : arg.prevState.currentExecutionCount;
     arg.queueAction(
         createPostableAction(InteractiveWindowMessages.GetVariablesRequest, {
             executionCount: newExecutionCount,
@@ -108,7 +108,12 @@ function handleResponse(arg: VariableReducerArg<IJupyterVariablesResponse>): IVa
 function handleRestarted(arg: VariableReducerArg): IVariableState {
     // If the variables are visible, refresh them
     if (arg.prevState.visible) {
-        return handleRequest({ ...arg, payload: { executionCount: 0, sortColumn: 'name', sortAscending: true, startIndex: 0, pageSize: arg.prevState.pageSize } });
+        const result = handleRequest({ ...arg, payload: { executionCount: 0, sortColumn: 'name', sortAscending: true, startIndex: 0, pageSize: arg.prevState.pageSize } });
+        return {
+            ...result,
+            currentExecutionCount: 0,
+            variables: []
+        };
     }
     return arg.prevState;
 }