Hot-reload

[PaulBlanche]

In dev mode, use SSE to trigger refresh on rebuild. Not HMR, but this should allow rapid developpment cycle.

[PaulBlanche]

In order to implement this without over-engineering, we need denoland/deno#8327.

Currently, with a server started, we can listen to changes on a filesystem and trigger a rebuild. This rebuild is done with the cached modules loaded by Deno. This means that we will react to a change to a module, but a refresh will produce the old page (because the module cache was populated with the old module).

As a workaround we could run frugal in a worker and the server in the main thread. Instead of invoking frugal methods, the server would exchange messages with a worker. When a filesystem event is triggered, we destroy and recreate the worker. But i think it's not a good idea :

• This might be difficult (or impossible) since we might need to pass function between the main thread an the worker.
• destroying/recreating the worker might be expensive.

[PaulBlanche]

Solution implemented in #18.

Starting frugal in dev mode starts a livereload server and generates a module that will be run as a subprocess in watch mode (meaning the module cache is reloaded on each filesystem change event). Parent and subprocess exchange messages through stdin/stdout. The subprocess sends a message each time it reloads (due to filesystem change event), and the livereload server can dispatch a SSE.

The livereload client is "side loaded" if frugal is started in dev mode, and triggers a page reload.