Error in `execute_cell` and `insert_execute_cell` tools on `main` branch

[eleonorecharles]

A regression has been introduced in the main branch (still unreleased code) that causes errors in the execute_cell and insert_execute_cell tools.

code_to_execute = cell_source.to_py()                                              

AttributeError: 'str' object has no attribute 'to_py'     

[ChengJiale150]

Occur in execute_code_tools.py, in Jupyter Server Mode using YDoc and RTC.

            if ydoc:
                # Notebook is open - use YDoc and RTC
                logger.info(f"Notebook {file_id} is open, using RTC mode")
                
                num_cells = len(ydoc.ycells)
                if cell_index >= num_cells:
                    raise ValueError(f"Cell index {cell_index} out of range (notebook has {num_cells} cells)")

                cell_id = ydoc.ycells[cell_index].get("id")
                cell_source = ydoc.ycells[cell_index].get("source")

                if not cell_source or not cell_source.to_py().strip():
                    return []

                code_to_execute = cell_source.to_py()
                document_id = f"json:notebook:{file_id}"

                # Execute with RTC metadata - outputs will sync automatically
                outputs = await execute_via_execution_stack(
                    serverapp=serverapp,
                    kernel_id=kernel_id,
                    code=code_to_execute,
                    document_id=document_id,
                    cell_id=cell_id,
                    timeout=timeout_seconds
                )

                return outputs

[ChengJiale150]

It seem that the type of cell_source returned by ydoc.ycells[cell_index].get("source") is str not other type. It can fix by simply add this:

if isinstance(cell_source,str):
    code_to_execute = cell_source
else:
    code_to_execute = cell_source.to_py()

And It still seem that YDoc and RTC Mode is still not successfully opened in CI test.