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Rich-Harrisdummdidumm
Rich-Harris
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dummdidumm
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feat: universal injected css (#12374)
* chore: reenable server CSS output through a compiler option There are various use cases where this continues to be necessary/nice to have: - rendering OG cards - rendering emails - basically anything where you use `render` manually and want to quickly stitch together the CSS without setting up an elaborate tooling chain * cssRenderOnServer -> css: 'injected' * update tests * move append_styles into new module, update implementation * get HMR working * don't append styles to head when compiling as a custom element * update changeset * tweak * tweak * tweak wording * update test * fix * reinstate optimisation, but without the bug * fix sourcemap test * move breaking change note * Update packages/svelte/src/internal/server/index.js Co-authored-by: Simon H <[email protected]> --------- Co-authored-by: Simon Holthausen <[email protected]> Co-authored-by: Simon H <[email protected]>
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‎.changeset/rich-taxis-hear.md

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---
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'svelte': patch
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---
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feat: include CSS in `<head>` when `css: 'injected'`

‎packages/svelte/src/compiler/phases/3-transform/client/transform-client.js

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@@ -332,22 +332,16 @@ export function client_component(source, analysis, options) {
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}
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}
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335-
const append_styles =
336-
analysis.inject_styles && analysis.css.ast
337-
? () =>
338-
component_block.body.push(
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b.stmt(
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b.call(
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'$.append_styles',
342-
b.id('$$anchor'),
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b.literal(analysis.css.hash),
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b.literal(render_stylesheet(source, analysis, options).code)
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)
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)
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)
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: () => {};
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if (analysis.css.ast !== null && analysis.inject_styles) {
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const hash = b.literal(analysis.css.hash);
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const code = b.literal(render_stylesheet(analysis.source, analysis, options).code);
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350-
append_styles();
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state.hoisted.push(b.const('$$css', b.object([b.init('hash', hash), b.init('code', code)])));
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component_block.body.unshift(
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b.stmt(b.call('$.append_styles', b.id('$$anchor'), b.id('$$css')))
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);
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}
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const should_inject_context =
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analysis.needs_context ||
@@ -423,17 +417,34 @@ export function client_component(source, analysis, options) {
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);
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if (options.hmr) {
426-
const accept_fn = b.arrow(
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[b.id('module')],
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b.block([b.stmt(b.call('$.set', b.id('s'), b.member(b.id('module'), b.id('default'))))])
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);
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const accept_fn_body = [
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b.stmt(b.call('$.set', b.id('s'), b.member(b.id('module'), b.id('default'))))
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];
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if (analysis.css.hash) {
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// remove existing `<style>` element, in case CSS changed
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accept_fn_body.unshift(
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b.stmt(
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b.call(
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b.member(
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b.call('document.querySelector', b.literal('#' + analysis.css.hash)),
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b.id('remove'),
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false,
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true
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)
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)
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)
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);
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}
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body.push(
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component,
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b.if(
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b.id('import.meta.hot'),
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b.block([
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b.const(b.id('s'), b.call('$.source', b.id(analysis.name))),
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b.const(b.id('filename'), b.member(b.id(analysis.name), b.id('filename'))),
447+
b.const(b.id('accept'), b.arrow([b.id('module')], b.block(accept_fn_body))),
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b.stmt(b.assignment('=', b.id(analysis.name), b.call('$.hmr', b.id('s')))),
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b.stmt(
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b.assignment('=', b.member(b.id(analysis.name), b.id('filename')), b.id('filename'))
@@ -442,10 +453,14 @@ export function client_component(source, analysis, options) {
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b.id('import.meta.hot.acceptExports'),
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b.block([
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b.stmt(
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b.call('import.meta.hot.acceptExports', b.array([b.literal('default')]), accept_fn)
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b.call(
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'import.meta.hot.acceptExports',
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b.array([b.literal('default')]),
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b.id('accept')
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)
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)
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]),
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b.block([b.stmt(b.call('import.meta.hot.accept', accept_fn))])
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b.block([b.stmt(b.call('import.meta.hot.accept', b.id('accept')))])
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)
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])
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),

‎packages/svelte/src/compiler/phases/3-transform/server/transform-server.js

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@@ -39,6 +39,7 @@ import {
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BLOCK_OPEN_ELSE
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} from '../../../../internal/server/hydration.js';
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import { filename, locator } from '../../../state.js';
42+
import { render_stylesheet } from '../css/index.js';
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/** Opens an if/each block, so that we can remove nodes in the case of a mismatch */
4445
const block_open = b.literal(BLOCK_OPEN);
@@ -2158,6 +2159,14 @@ export function server_component(analysis, options) {
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const body = [...state.hoisted, ...module.body];
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2162+
if (analysis.css.ast !== null && options.css === 'injected' && !options.customElement) {
2163+
const hash = b.literal(analysis.css.hash);
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const code = b.literal(render_stylesheet(analysis.source, analysis, options).code);
2165+
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body.push(b.const('$$css', b.object([b.init('hash', hash), b.init('code', code)])));
2167+
component_block.body.unshift(b.stmt(b.call('$$payload.css.add', b.id('$$css'))));
2168+
}
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let should_inject_props =
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should_inject_context ||
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props.length > 0 ||

‎packages/svelte/src/compiler/types/index.d.ts

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@@ -99,8 +99,8 @@ export interface CompileOptions extends ModuleCompileOptions {
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*/
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immutable?: boolean;
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/**
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* - `'injected'`: styles will be included in the JavaScript class and injected at runtime for the components actually rendered.
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* - `'external'`: the CSS will be returned in the `css` field of the compilation result. Most Svelte bundler plugins will set this to `'external'` and use the CSS that is statically generated for better performance, as it will result in smaller JavaScript bundles and the output can be served as cacheable `.css` files.
102+
* - `'injected'`: styles will be included in the `head` when using `render(...)`, and injected into the document (if not already present) when the component mounts. For components compiled as custom elements, styles are injected to the shadow root.
103+
* - `'external'`: the CSS will only be returned in the `css` field of the compilation result. Most Svelte bundler plugins will set this to `'external'` and use the CSS that is statically generated for better performance, as it will result in smaller JavaScript bundles and the output can be served as cacheable `.css` files.
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* This is always `'injected'` when compiling with `customElement` mode.
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*/
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css?: 'injected' | 'external';

‎packages/svelte/src/internal/client/dom/css.js

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import { DEV } from 'esm-env';
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import { queue_micro_task } from './task.js';
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var seen = new Set();
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/**
7+
* @param {Node} anchor
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* @param {{ hash: string, code: string }} css
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*/
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export function append_styles(anchor, css) {
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// in dev, always check the DOM, so that styles can be replaced with HMR
12+
if (!DEV) {
13+
if (seen.has(css)) return;
14+
seen.add(css);
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}
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17+
// Use `queue_micro_task` to ensure `anchor` is in the DOM, otherwise getRootNode() will yield wrong results
18+
queue_micro_task(() => {
19+
var root = anchor.getRootNode();
20+
21+
var target = /** @type {ShadowRoot} */ (root).host
22+
? /** @type {ShadowRoot} */ (root)
23+
: /** @type {Document} */ (root).head;
24+
25+
if (!target.querySelector('#' + css.hash)) {
26+
const style = document.createElement('style');
27+
style.id = css.hash;
28+
style.textContent = css.code;
29+
30+
target.appendChild(style);
31+
}
32+
});
33+
}

‎packages/svelte/src/internal/client/index.js

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@@ -20,6 +20,7 @@ export { snippet, wrap_snippet } from './dom/blocks/snippet.js';
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export { component } from './dom/blocks/svelte-component.js';
2121
export { element } from './dom/blocks/svelte-element.js';
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export { head } from './dom/blocks/svelte-head.js';
23+
export { append_styles } from './dom/css.js';
2324
export { action } from './dom/elements/actions.js';
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export {
2526
remove_input_defaults,
@@ -120,7 +121,7 @@ export {
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update_pre_store,
121122
update_store
122123
} from './reactivity/store.js';
123-
export { append_styles, set_text } from './render.js';
124+
export { set_text } from './render.js';
124125
export {
125126
get,
126127
invalidate_inner_signals,

‎packages/svelte/src/internal/client/render.js

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@@ -22,6 +22,7 @@ import * as w from './warnings.js';
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import * as e from './errors.js';
2323
import { validate_component } from '../shared/validate.js';
2424
import { assign_nodes } from './dom/template.js';
25+
import { queue_micro_task } from './dom/task.js';
2526

2627
/** @type {Set<string>} */
2728
export const all_registered_events = new Set();
@@ -294,35 +295,3 @@ export function unmount(component) {
294295
}
295296
fn?.();
296297
}
297-
298-
/**
299-
* @param {Node} target
300-
* @param {string} style_sheet_id
301-
* @param {string} styles
302-
*/
303-
export async function append_styles(target, style_sheet_id, styles) {
304-
// Wait a tick so that the template is added to the dom, else getRootNode() will yield wrong results
305-
// If it turns out that this results in noticeable flickering, we need to do something like doing the
306-
// append outside and adding code in mount that appends all stylesheets (similar to how we do it with event delegation)
307-
await Promise.resolve();
308-
const append_styles_to = get_root_for_style(target);
309-
if (!append_styles_to.getElementById(style_sheet_id)) {
310-
const style = document.createElement('style');
311-
style.id = style_sheet_id;
312-
style.textContent = styles;
313-
const target = /** @type {Document} */ (append_styles_to).head || append_styles_to;
314-
target.appendChild(style);
315-
}
316-
}
317-
318-
/**
319-
* @param {Node} node
320-
*/
321-
function get_root_for_style(node) {
322-
if (!node) return document;
323-
const root = node.getRootNode ? node.getRootNode() : node.ownerDocument;
324-
if (root && /** @type {ShadowRoot} */ (root).host) {
325-
return /** @type {ShadowRoot} */ (root);
326-
}
327-
return /** @type {Document} */ (node.ownerDocument);
328-
}

‎packages/svelte/src/internal/server/index.js

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@@ -43,9 +43,10 @@ export const VoidElements = new Set([
4343
* @param {Payload} to_copy
4444
* @returns {Payload}
4545
*/
46-
export function copy_payload({ out, head }) {
46+
export function copy_payload({ out, css, head }) {
4747
return {
4848
out,
49+
css: new Set(css),
4950
head: {
5051
title: head.title,
5152
out: head.out
@@ -107,7 +108,7 @@ export let on_destroy = [];
107108
*/
108109
export function render(component, options = {}) {
109110
/** @type {Payload} */
110-
const payload = { out: '', head: { title: '', out: '' } };
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const payload = { out: '', css: new Set(), head: { title: '', out: '' } };
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112113
const prev_on_destroy = on_destroy;
113114
on_destroy = [];
@@ -129,8 +130,14 @@ export function render(component, options = {}) {
129130
for (const cleanup of on_destroy) cleanup();
130131
on_destroy = prev_on_destroy;
131132

133+
let head = payload.head.out + payload.head.title;
134+
135+
for (const { hash, code } of payload.css) {
136+
head += `<style id="${hash}">${code}</style>`;
137+
}
138+
132139
return {
133-
head: payload.head.out || payload.head.title ? payload.head.out + payload.head.title : '',
140+
head,
134141
html: payload.out,
135142
body: payload.out
136143
};

‎packages/svelte/src/internal/server/types.d.ts

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@@ -13,6 +13,7 @@ export interface Component {
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1414
export interface Payload {
1515
out: string;
16+
css: Set<{ hash: string; code: string }>;
1617
head: {
1718
title: string;
1819
out: string;

‎packages/svelte/tests/server-side-rendering/samples/css-empty/_config.js

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1+
import { test } from '../../test';
2+
3+
// Test validates that by default no CSS is rendered on the server
4+
export default test({});

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