Rendering HTML from Svelte SSR

[jimafisk]

Hi @matthewmueller!

I was exploring how I might leverage your V8 / Svelte compilation in Plenti. Your API is really nicely written 👌

Simple example compiling Svelte files from a "templates" folder to an "output" folder

package main

import (
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"

	v8 "github.com/livebud/bud/package/js/v8"
	"github.com/livebud/bud/package/svelte"
)

func main() {
	vm, _ := v8.Load()
	svelteCompiler, _ := svelte.Load(vm)

	filepath.Walk("templates", func(path string, info os.FileInfo, err error) error {
		if !info.IsDir() && filepath.Ext(path) == ".svelte" {
			fileContents, _ := os.ReadFile(path)
			destPath := "output" + strings.TrimPrefix(path, "templates")
			os.MkdirAll(filepath.Dir(destPath), os.ModePerm)

			DOM, _ := svelteCompiler.DOM(path, fileContents)
			ioutil.WriteFile(strings.TrimSuffix(destPath, ".svelte")+"_DOM.js", []byte(DOM.JS), os.ModePerm)

			SSR, _ := svelteCompiler.SSR(path, fileContents)
			ioutil.WriteFile(strings.TrimSuffix(destPath, ".svelte")+"_SSR.js", []byte(SSR.JS), os.ModePerm)
		}
		return nil
	})
}

My question: Is there a way to run Component.render(props) from your svelte package to generate HTML? Thank you!

Related issues:

• How is svelte being server side rendered? #246
• Server side rendering #23

[matthewmueller]

Hey @jimafisk 🙂

So those functions are for compiling one Svelte file. I'm guessing in Plenti, you'll want to support imports as well. To do that you'll need to wrap those functions as plugins in ESBuild to get one large blob of bundle JS.

You can find that code here:

bud/framework/view/ssr/ssr.go

Line 55 in 2cc8d0a

func (c *Generator) Compile(fsys fileSystem) ([]byte, error) {

(The transformer contains the Svelte compiler)

Once you have that blob of JS, you can call v8.Eval on it:

bud/framework/view/ssr/ssr_test.go

Line 132 in 2cc8d0a

result, err := vm.Eval("render.js", string(code)+`; bud.render("`+path+`", `+string(input)+`)`)

That would call Component.render() and return HTML.