Assets need deploy-time building

[jace]

Baseframe makes extensive use of WebAssets, forcing it on all apps. WebAssets is currently configured to build assets on demand at run-time. This interferes with read-only filesystems such as in Docker.

We need WebAssets to do asset building as a distinct step as part of the deployment, or replace it with something else that can do that, like Webpack.

[jace]

WebAssets has a note on how to make it work with read-only filesystems. We could add this as a command to manage.py in Coaster. https://webassets.readthedocs.io/en/latest/faq.html#is-google-app-engine-supported

[jace]

The notes on URL expiry and cache manifests are also relevant: https://webassets.readthedocs.io/en/latest/expiring.html

[shreyas-satish]

From my reading, here are some features webpack offers over webassets:

1. Hot Module Replacement
2. Code splitting
3. Source maps for JS

There's a plugin that helps retrieve the latest built assets with a jinja helper - https://github.com/nickjj/flask-webpack. I'm currently learning how to configure this and webpack with a flask app.

[jace]

Should we provide a two-part upgrade path for existing apps?

1. Switch to webassets with static compilation via manage.py for all existing apps; no code change necessary in apps.
2. Allow replacing webassets with webpack for apps that are JS-heavy.

This is assuming webpack is not a drop-in replacement and apps will need upgrades. If that's not the case, we can switch entirely.