Jupyter Notebook: Fix window.Plotly not defined error when running all cells

[dalogsdon]

In Dynamic Dashboards (jupyter/dashboards_server#108) we need to be able to execute all code cells of a Jupyter Notebook file. Currently Plotly does not work, with the error that window.Plotly is not defined. This problem can also be observed in a notebook when performing a "Run All" of all cells.

@jdfreder's fix in #412 preserves requirejs when plotting in offline mode in the notebook, but causes an error if doing a "Run All" cells. The reason for this is the initialization of window.Plotly occurs in a requirejs function and is immediately followed by an attempt to access it outside of a requirejs function. At this point window.Plotly won't yet be defined since the definition will execute asynchronously after the attempt to access it.

To fix, the call to Plotly.newPlot() could happen inside its own requrejs function, making use of the 'plotly' requirejs module. I have made the minimal change in this PR to demonstrate. (I kept the requirejs function that defines window.Plotly, but it could potentially be removed in favor of using the requirejs module only.) It works for me when doing a "Run All" in the notebook and also works when deploying a dashboard read from the notebook file.

This may also be related to #394 if the conversion of notebook to slides is doing a "Run All".

[jdfreder]

Thanks @dalogsdon , 👍

[theengineear]

@jdfreder , does this need to wait on any dev you're doing, or can we merge this in now?

[jdfreder]

@theengineear thanks for asking, but no, it doesn't, go ahead and merge away :)

[theengineear]

great, thx!