hydratable.js — svelte Source File

Source Code

/** @import { HydratableLookupEntry } from '#server' */
import { async_mode_flag } from '../flags/index.js';
import { get_render_context } from './render-context.js';
import * as e from './errors.js';
import * as devalue from 'devalue';
import { get_stack } from '../shared/dev.js';
import { DEV } from 'esm-env';
import { get_user_code_location } from './dev.js';

/**
 * @template T
 * @param {string} key
 * @param {() => T} fn
 * @returns {T}
 */
export function hydratable(key, fn) {
	if (!async_mode_flag) {
		e.experimental_async_required('hydratable');
	}

	const { hydratable } = get_render_context();

	let entry = hydratable.lookup.get(key);

	if (entry !== undefined) {
		if (DEV) {
			const comparison = compare(key, entry, encode(key, fn()));
			comparison.catch(() => {});
			hydratable.comparisons.push(comparison);
		}

		return /** @type {T} */ (entry.value);
	}

	const value = fn();

	entry = encode(key, value, hydratable.unresolved_promises);
	hydratable.lookup.set(key, entry);

	return value;
}

/**
 * @param {string} key
 * @param {any} value
 * @param {Map<Promise<any>, string>} [unresolved]
 */
function encode(key, value, unresolved) {
	/** @type {HydratableLookupEntry} */
	const entry = { value, serialized: '' };

	if (DEV) {
		entry.stack = get_user_code_location();
	}

	let uid = 1;

	entry.serialized = devalue.uneval(entry.value, (value, uneval) => {
		if (is_promise(value)) {
			// we serialize promises as `"${i}"`, because it's impossible for that string
// ... (83 more lines)