.changeset/worker-template-compiler.md

@@ -0,0 +1,7 @@
+---
+"@luzzle/web.worker": patch
+---
+
+Add worker-owned compilation of Svelte templates into standalone server-rendering
+modules. The worker bundles the matching Svelte runtime with esbuild; no template
+job, publishing lifecycle, or live web integration is enabled by this change.

packages/web/worker/README.md

@@ -26,14 +26,28 @@ The worker isolates intensive CPU/IO tasks from the SvelteKit app, including:
 The worker registers and processes the following job types:
 
 1. **`publish`** — Triggers the orchestrator pipeline to synchronize the archive
- from/to remotes, parse changes, build CDN asset variants, and sync CDN.
+   from/to remotes, parse changes, build CDN asset variants, and sync CDN.
 2. **`preview`** — Performs hot-path parsing of piece modifications in the
- editor, returning on-the-fly syntax-highlighted HTML and asset preview URLs.
+   editor, returning on-the-fly syntax-highlighted HTML and asset preview URLs.
 3. **`job-progress-purge`** — Clean-up job to purge completed/failed workflow
- job logs based on a retention schedule.
+   job logs based on a retention schedule.
 
 ---
 
+## Template compiler
+
+`src/templates/compile.ts` contains a low-level `compileTemplate(source, filename)`
+function. It uses the worker's Svelte compiler and esbuild to return a standalone
+Node ESM module as `code`, alongside the Svelte source `warnings`.
+
+The generated module exports `render(props)`, which synchronously returns plain
+`{ body, head }` strings. `head` includes injected component CSS. Svelte's server
+runtime is bundled into that module; callers do not need to install Svelte.
+
+This utility does not read configuration, validate the supported authoring subset,
+cache/publish revisions, or register a background job. Open Graph and thumbnail
+processing are unchanged. Template source is trusted site-owner code, not sandboxed.
+
 ## Operations 🛠️
 
 The worker executes inside the `luzzle-worker` Docker container. For

packages/web/worker/package.json

@@ -48,6 +48,7 @@
 		"@takumi-rs/core": "1.5.0",
 		"colorlip": "^1.0.0",
 		"devlop": "1.1.0",
+		"esbuild": "0.25.12",
 		"hastscript": "9.0.1",
 		"kysely": "0.28.17",
 		"mdast-util-from-markdown": "2.0.2",

packages/web/worker/src/templates/compile.test.ts

@@ -0,0 +1,76 @@
+import { describe, expect, test } from 'vitest'
+import { execFile } from 'node:child_process'
+import { mkdir, mkdtemp, readFile, rm, writeFile } from 'node:fs/promises'
+import path from 'node:path'
+import { fileURLToPath, pathToFileURL } from 'node:url'
+import { promisify } from 'node:util'
+import { compileTemplate } from './compile.js'
+
+const exec = promisify(execFile)
+const fixture = new URL('../../test/fixtures/templates/page.svelte', import.meta.url)
+
+// A native Node process, not Vitest's module loader. Any dependency left outside
+// the artifact must be a Node builtin, even if the workspace could resolve it.
+const runArtifact = `
+import { isBuiltin, registerHooks } from 'node:module';
+const moduleUrl = process.argv[1];
+registerHooks({
+	resolve(specifier, context, nextResolve) {
+		if (specifier !== moduleUrl && !isBuiltin(specifier)) {
+			throw new Error('Artifact has an external dependency: ' + specifier);
+		}
+		return nextResolve(specifier, context);
+	}
+});
+const { render } = await import(moduleUrl);
+const first = render({ data: { piece: { type: 'custom-one', title: '<First>&' } } });
+const second = render({ data: { piece: { type: 'another-kind', title: 'Second' } } });
+console.log(JSON.stringify({ first, second }));
+`
+
+describe('compileTemplate', () => {
+	test('produces a standalone renderer with escaped content and scoped CSS', async () => {
+		const source = await readFile(fixture, 'utf8')
+		const compiled = await compileTemplate(source, fileURLToPath(fixture))
+		expect(compiled.warnings).toEqual([])
+
+		const cache = fileURLToPath(new URL('../../node_modules/.cache/', import.meta.url))
+		await mkdir(cache, { recursive: true })
+		const directory = await mkdtemp(path.join(cache, 'template-'))
+		try {
+			const modulePath = path.join(directory, 'renderer.mjs')
+			await writeFile(modulePath, compiled.code)
+			const { stdout } = await exec(process.execPath, [
+				'--input-type=module',
+				'-e',
+				runArtifact,
+				pathToFileURL(modulePath).href,
+			])
+			const { first, second } = JSON.parse(stdout)
+			expect(Object.keys(first).sort()).toEqual(['body', 'head'])
+			expect(first.body).toContain('custom-one: &lt;First>&amp;')
+			expect(first.body).toMatch(/class="piece svelte-/)
+			expect(first.head).toContain('--color-primary')
+			expect(first.head).toContain('<style')
+			expect(second.body).toContain('another-kind: Second')
+			expect(second.body).not.toContain('First')
+		} finally {
+			await rm(directory, { recursive: true, force: true })
+		}
+	})
+
+	test('preserves Svelte source warnings for the caller', async () => {
+		const source = '<p>Hello</p><style>.unused { color: var(--color-primary); }</style>'
+		const compiled = await compileTemplate(source, 'unused.svelte')
+		expect(compiled.warnings).toEqual([
+			expect.objectContaining({ code: 'css_unused_selector', filename: 'unused.svelte' }),
+		])
+	})
+
+	test('reports invalid source with its original filename', async () => {
+		await expect(compileTemplate('<div>', 'broken.svelte')).rejects.toMatchObject({
+			code: 'element_unclosed',
+			filename: 'broken.svelte',
+		})
+	})
+})

packages/web/worker/src/templates/compile.ts

@@ -0,0 +1,57 @@
+import { build } from 'esbuild'
+import { compile, type Warning } from 'svelte/compiler'
+
+export interface CompiledTemplate {
+	code: string
+	warnings: Warning[]
+}
+
+const templateModuleId = 'luzzle:template'
+const renderEntry = `
+import Template from '${templateModuleId}';
+import { render as renderSvelte } from 'svelte/server';
+
+export function render(props) {
+	const { body, head } = renderSvelte(Template, { props });
+	return { body, head };
+}
+`
+
+export async function compileTemplate(source: string, filename: string): Promise<CompiledTemplate> {
+	const compiled = compile(source, {
+		filename,
+		generate: 'server',
+		css: 'injected',
+		dev: false,
+		experimental: { async: false },
+	})
+
+	const bundled = await build({
+		stdin: { contents: renderEntry, resolveDir: import.meta.dirname },
+		bundle: true,
+		write: false,
+		platform: 'node',
+		format: 'esm',
+		target: 'node24',
+		conditions: ['node', 'production'],
+		define: { 'process.env.NODE_ENV': '"production"' },
+		plugins: [
+			{
+				name: 'compiled-template',
+				setup(builder) {
+					builder.onResolve({ filter: new RegExp(`^${templateModuleId}$`) }, () => ({
+						path: filename,
+						namespace: templateModuleId,
+					}))
+					builder.onLoad({ filter: /.*/, namespace: templateModuleId }, () => ({
+						contents: compiled.js.code,
+						loader: 'js',
+						resolveDir: import.meta.dirname,
+					}))
+				},
+			},
+		],
+	})
+
+	return { code: bundled.outputFiles[0].text, warnings: compiled.warnings }
+}

packages/web/worker/test/fixtures/templates/page.svelte

@@ -0,0 +1,12 @@
+<script>
+	let { data } = $props()
+	const label = $derived(`${data.piece.type}: ${data.piece.title}`)
+</script>
+
+<article class="piece">{label}</article>
+
+<style>
+	.piece {
+		color: var(--color-primary);
+	}
+</style>

packages/web/worker/vite.config.ts

@@ -14,6 +14,7 @@ export default defineConfig({
 				'dist/**',
 				'node_modules/**',
 				'coverage/**',
+				'test/fixtures/**',
 				'**/*.d.ts',
 				'src/index.ts',
 				'src/pieces/.compiled/**',

pnpm-lock.yaml

@@ -779,6 +779,9 @@ importers:
       devlop:
         specifier: 1.1.0
         version: 1.1.0
+      esbuild:
+        specifier: 0.25.12
+        version: 0.25.12
       hastscript:
         specifier: 9.0.1
         version: 9.0.1