Dev-mode livereload

framework.NewApp() and uihost.New() auto-wire a tiny SSE-based
livereload pair when the process is running under gofastr dev. Edit
a .go file, the binary restarts, and every open browser tab refreshes
on its own — no host-app code required.

How it turns on

Three env vars decide. All defaults are dev-friendly; production is
always safe:

VarDefaultMeaning
GOFASTR_DEVunsetgofastr dev sets this to 1 on the child process. Without it, livereload stays dormant.
GOFASTR_ENVunsetSet to production to force livereload off even if GOFASTR_DEV slips through. Belt-and-suspenders for accidental dev binaries in prod.
GOFASTR_DEV_LIVERELOADunset (= on)Set to 0 to opt out while keeping the rest of dev mode (gofastr dev's rebuild loop) running.

Predicate (single source of truth in framework/dev/livereload.go):

3 lines
GOFASTR_ENV != "production"  ANDGOFASTR_DEV truthy           ANDGOFASTR_DEV_LIVERELOAD != "0"

What it does

When enabled:

  • framework.NewApp() registers two routes on the App router:
    - GET /__livereload — text/event-stream. Fires one event: ready
    on connect, then idles with a 25s SSE-comment heartbeat. Closes
    when the request context cancels (server shutdown / browser tab
    close).
    - GET /__livereload.js — ~16 lines of JS. Opens an EventSource,
    treats the second onopen (i.e. the reconnect after the
    server drop) as the reload signal, calls location.reload().
  • uihost.New() auto-appends /__livereload.js to the extraScripts
    list so every rendered page links to the client script before
    </body>. CSP-safe — it's a <script src="...">, no inline JS.

One persistent SSE connection per tab, near-zero idle traffic, no
polling.

How gofastr dev wires it

cmd/gofastr/dev.go injects GOFASTR_DEV=1 into the child binary's
environment when it launches the rebuilt server. The host app doesn't
need to forward, set, or check the flag — it's transparent.

Opting out

2 lines
# Keep rebuild-on-save but disable browser refresh:GOFASTR_DEV_LIVERELOAD=0 gofastr dev

Forcing it on outside gofastr dev

For a custom watcher or air-style tool, set the env yourself:

1 lines
GOFASTR_DEV=1 ./my-app

The framework will auto-register the routes and inject the script.
Browser tabs already pointing at the app reload as soon as the new
binary accepts the SSE connection.

Common mistakes

  • Setting GOFASTR_ENV=production while expecting livereload to work
    in dev. Production is a hard kill switch; clear the var first.
  • Wiring uihost.WithExtraScripts("/__livereload.js") by hand. The
    framework already does it when env says so — your manual call
    becomes a duplicate <script> tag.
  • Registering /__livereload routes by hand. The framework already
    does it — a manual Router().Get will collide.
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