Anchor is optional

Author: fcollonval

sidecar/sidecar.py

@@ -26,5 +26,5 @@ class Sidecar(Output):
     anchor = CaselessStrEnum(
         ['split-right', 'split-left', 'split-top', 'split-bottom', 'tab-before', 'tab-after', 'right'],
         default_value='right', 
-        allow_none=False
+        allow_none=True
     ).tag(sync=True)

src/plugin.ts

@@ -65,7 +65,7 @@ function activateWidgetExtension(app: JupyterLab, registry: IJupyterWidgetRegist
               v._outputView.activate();
             });
           } else {
-            let anchor = this.model.get('anchor');
+            let anchor = this.model.get('anchor') || 'right';
             if(anchor === 'right'){
               app.shell.add(w, 'right');
               app.shell.expandRight();