Investigate ESM support in bokehjs' build

Based on discussion in PR #8782.

TypeError: FlatBush is not a constructor

The underlying problem is that flatbush uses an experimental module field in its package.json to define the ES module entry point, along with the standard main field. webpack and similar linkers seem to prefer module over main, despite its non-standard nature. I will need to do proper research on this subject to decide whether this is a good idea for us to support the module field or not (currently I’m leaning towards the later, due to non-standard by default nature). One can fix this issue on the client side by setting up the linker (assuming webpack) with:

{ resolve: { mainFields: ['main', 'module'] } }

For rollup etc. similar configuration option should be hopefully possible.

[davegravy]

I ran into this issue.

FWIW I use create-react-app and my (limited) understanding is that modifying webpack config isn’t possible without ‘ejecting’ the project (which I want to avoid for now). If there’s another solution I’m all ears.

[fbove]

I would need to get a reproducible example to decide if this is an issue or not.

A clean webpack project which uses bokehjs with sample data from Bokeh docs: https://github.com/fbove/bokehjs-example

Hope it helps!