Behaviour for Svelte render backends.

A renderer knows how to turn raw component assigns (name, props, slots, options) into a prepared assigns map that downstream code — usually the CaravelaSvelte.svelte/1 function component — uses to emit the final output.

The seam exists so CaravelaSvelte.Rest (Phase B.2) can reuse the same SSR pipeline and client-payload packaging, but emit a Plug.Conn response instead of HEEx.

Today the only implementation is CaravelaSvelte.Live, which preserves the behaviour live_svelte has always had.

Prepared assigns shape

The prepared assigns map MUST include every key the CaravelaSvelte.svelte/1 template reads:

• :init — true on first render / dead render
• :slots — decoded slot map
• :ssr_render — result of SSR (or nil when disabled)
• :svelte_id — stable DOM id
• :props_to_send — map that will be JSON-encoded onto data-props
• :use_diff — boolean flag
• :props_diff — compressed JSON-patch ops list
• :streams_diff — compressed stream patch ops list

Plus whatever the original assigns carried (name, class, etc.).

Configuration

The default renderer is CaravelaSvelte.Live. Override per-app:

config :caravela_svelte, :renderer, MyApp.CustomRenderer