Summary:
This commit adds a simple Python server for connecting the output of
`yarn api` (or `yarn api --watch`) to an observable notebook. We need a
custom server rather than just `python3 -m http.server` to send CORS
headers properly. This server enables a very tight loop from editing
SourceCred core code on your local filesystem to seeing live updates in
an Observable notebook, with latency on the order of one second.
Test Plan:
Run `yarn api --watch` in the background. Launch the new API server.
Navigate to <https://observablehq.com/demo>. Copy the two paragraphs of
Observable code from `scripts/serve_api.py` into _separate_ Observable
cells, and execute them. Note that `myGraph` becomes a valid SourceCred
graph. Modify `src/core/graph.js` to add `this._aaa = 123;` to the top
of the `Graph` constructor. Re-execute the first Observable cell (the
one that loads the SourceCred module), and note that `myGraph` updates
to include the new `_aaa` attribute:
![Screenshot of Observable notebook after test plan][ss]
[ss]: https://user-images.githubusercontent.com/4317806/71958748-dddf8680-31a5-11ea-9016-5df76ceeea46.png
wchargin-branch: api-server
William Chargin
