Freeze: frozen cells are always unlocked when notebook is loaded

[yacchin1205]

migrate_state function always unlocks an editable attribute, because the code below is executed even if there are no cell.metadata.run_control.read_only.

cell.metadata.editable = !cell.metadata.run_control.read_only;

https://github.com/ipython-contrib/jupyter_contrib_nbextensions/blob/master/src/jupyter_contrib_nbextensions/nbextensions/freeze/main.js#L59

As a result, the editable metadata is set to true, and the get_state function returns normal for the cell after reloaded.

I assume that it is executed only when the metadata has run_control.read_only (with old metadata format).

[jcb91]

Yes, you're absolutely right, it should have read something more like

if (cell.metadata.run_control.read_only === true) {
    cell.metadata.editable = false;
}

[yacchin1205]

@jcb91 Thank you for reviewing! I've sent the PR.

I also found the error below, it seems that there are no checking whether the attribute is defined... the PR includes its fix also.

[Freeze] Error: TypeError: Cannot convert undefined or null to object
    at Function.keys (<anonymous>)
    at set_state (main.js?v=20170424120221:115)
    at initialize_states (main.js?v=20170424120221:154)
    at do_stuff_with_config (main.js?v=20170424120221:191)

[jcb91]

Thanks!