fix: resolve "no comm channel defined" error with plotly 6.x

Fixes posit-dev/py-shiny#2156

Plotly 6.0 switched FigureWidget to use anywidget, which doesn't have
a destroy() method. The previous cleanup logic only called v.remove()
for views with destroy(), causing anywidget-based views to skip removal
before m.close(). Since ipywidgets' close() deletes the comm before
removing views, the view removal would fail when trying to sync.

The fix ensures all views are removed while the comm is still available.

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: cpsievert

js/src/output.ts

@@ -222,8 +222,11 @@ Shiny.addCustomMessageHandler("shinywidgets_comm_close", async (msg_txt) => {
   try {
     const m = await model;
 
-    // Before .close()ing the model (which will .remove() each view), do some
-    // additional cleanup that .remove() might miss
+    // Remove all views BEFORE calling m.close(). This is critical because:
+    // 1. m.close() deletes the comm before removing views
+    // 2. When views are removed, they fire a 'remove' event that tries to sync _view_count
+    // 3. If the comm is already deleted, the sync fails with "no comm channel defined"
+    // By removing views first (while comm is still available), we avoid this error.
     await Promise.all(
       Object.values(m.views).map(async (viewPromise) => {
         try {
@@ -233,15 +236,15 @@ Shiny.addCustomMessageHandler("shinywidgets_comm_close", async (msg_txt) => {
           // https://github.com/plotly/plotly.py/pull/3805/files#diff-259c92d
           if (hasMethod<DestroyMethod>(v, 'destroy')) {
             v.destroy();
-            // Also, empirically, when this destroy() is relevant, it also helps to
-            // delete the view's reference to the model, I think this is the only
-            // way to drop the resize event listener (see the diff in the link above)
-            // https://github.com/posit-dev/py-shinywidgets/issues/166
-            delete v.model;
-            // Ensure sure the lm-Widget container is also removed
-            v.remove();
           }
 
+          // Remove the view while the comm is still available (so _view_count can sync)
+          v.remove();
+
+          // After remove(), delete the view's reference to the model to help with
+          // memory cleanup and to drop the resize event listener
+          // https://github.com/posit-dev/py-shinywidgets/issues/166
+          delete v.model;
 
         } catch (err) {
           console.error("Error cleaning up view:", err);