Fixed tab recreation logic and improved error handling

src/myfasthtml/controls/DataGridsManager.py

@@ -117,6 +117,29 @@ class DataGridsManager(MultipleInstance):
       # the selected node is not a document (it's a folder)
       return None
 
+  def create_tab_content(self, tab_id):
+    """
+    Recreate the content for a tab managed by this DataGridsManager.
+    Called by TabsManager when the content is not in cache (e.g., after restart).
+
+    Args:
+        tab_id: ID of the tab to recreate content for
+
+    Returns:
+        The recreated component (Panel with DataGrid)
+    """
+    # Find the document associated with this tab
+    document = next((d for d in self._state.elements if d.tab_id == tab_id), None)
+
+    if document is None:
+      raise ValueError(f"No document found for tab {tab_id}")
+
+    # Recreate the DataGrid with its saved state
+    dg = DataGrid(self._tabs_manager, _id=document.datagrid_id)
+
+    # Wrap in Panel
+    return Panel(self).set_main(dg)
+
   def clear_tree(self):
     self._state.elements = []
     self._tree.clear()

src/myfasthtml/controls/TabsManager.py

@@ -120,15 +120,36 @@ class TabsManager(MultipleInstance):
     if tab_config["component"] is None:
       return Div("Tab content does not support serialization.")
 
+    # 1. Try to get existing component instance
     res = InstancesManager.get(self._session, tab_config["component"][1], None)
     if res is not None:
+      logger.debug(f"Component {tab_config['component'][1]} already exists")
       return res
 
+    # 2. Get or create parent
+    if tab_config["component_parent"] is None:
+      logger.error(f"No parent defined for tab {tab_id}")
+      return Div("Failed to retrieve tab content.")
+
+    parent = InstancesManager.get(self._session, tab_config["component_parent"][1], None)
+    if parent is None:
+      logger.error(f"Parent {tab_config['component_parent'][1]} not found for tab {tab_id}")
+      return Div("Parent component not available")
+
+    # 3. If parent supports create_tab_content, use it
+    if hasattr(parent, 'create_tab_content'):
       try:
-      logger.debug(f"Component not created yet. Need to manually create it.")
-      return InstancesManager.dynamic_get(self._session, tab_config["component_parent"], tab_config["component"])
+        logger.debug(f"Asking parent {tab_config['component_parent'][1]} to create tab content for {tab_id}")
+        content = parent.create_tab_content(tab_id)
+        # Store in cache
+        self._state.ns_tabs_content[tab_id] = content
+        return content
       except Exception as e:
-      logger.error(f"Error while retrieving tab content: {e}")
+        logger.error(f"Error while parent creating tab content: {e}")
+        return Div("Failed to retrieve tab content.")
+    else:
+      # Parent doesn't support create_tab_content, fallback to error
+      logger.error(f"Parent {tab_config['component_parent'][1]} doesn't support create_tab_content")
       return Div("Failed to retrieve tab content.")
   
   def _get_or_create_tab_content(self, tab_id):

src/myfasthtml/core/instances.py

@@ -210,15 +210,24 @@ class InstancesManager:
   
   @staticmethod
   def dynamic_get(session, component_parent: tuple, component: tuple):
-    parent_type, parent_id = component_parent
     component_type, component_id = component
 
+    # 1. Check if component already exists
+    existing = InstancesManager.get(session, component_id, None)
+    if existing is not None:
+      logger.debug(f"Component {component_id} already exists, returning existing instance")
+      return existing
+
+    # 2. Component doesn't exist, create it
+    parent_type, parent_id = component_parent
+
     # parent should always exist
     parent = InstancesManager.get(session, parent_id)
 
     real_component_type = snake_to_pascal(component_type.removeprefix("mf-"))
     component_full_type = f"myfasthtml.controls.{real_component_type}.{real_component_type}"
     cls = get_class(component_full_type)
+    logger.debug(f"Creating new component {component_id} of type {real_component_type}")
     return cls(parent, _id=component_id)
   
   @staticmethod