Fix useId in JSX renderer

.changeset/friendly-queens-juggle.md

@@ -0,0 +1,5 @@
+---
+'preact-render-to-string': patch
+---
+
+Ensure `useId()` produces unique IDs when using the JSX renderer

src/pretty.js

@@ -16,8 +16,16 @@ import {
 	isDirty,
 	unsetDirty
 } from './lib/util.js';
-import { COMMIT, DIFF, DIFFED, RENDER, SKIP_EFFECTS } from './lib/constants.js';
-import { options, Fragment } from 'preact';
+import {
+	COMMIT,
+	DIFF,
+	DIFFED,
+	RENDER,
+	SKIP_EFFECTS,
+	PARENT,
+	CHILDREN
+} from './lib/constants.js';
+import { options, Fragment, h } from 'preact';
 
 // components without names, kept as a hash for later comparison to return consistent UnnamedComponentXX names.
 const UNNAMED = [];
@@ -47,8 +55,19 @@ export default function renderToStringPretty(vnode, context, opts, _inner) {
 	const previousSkipEffects = options[SKIP_EFFECTS];
 	options[SKIP_EFFECTS] = true;
 
+	const parent = h(Fragment, null);
+	parent[CHILDREN] = [vnode];
+
 	try {
-		return _renderToStringPretty(vnode, context || {}, opts, _inner);
+		return _renderToStringPretty(
+			vnode,
+			context || {},
+			opts,
+			_inner,
+			false,
+			undefined,
+			parent
+		);
 	} finally {
 		// options._commit, we don't schedule any effects in this library right now,
 		// so we can pass an empty queue to this hook.
@@ -64,7 +83,8 @@ function _renderToStringPretty(
 	opts,
 	inner,
 	isSvgMode,
-	selectValue
+	selectValue,
+	parent
 ) {
 	if (vnode == null || typeof vnode === 'boolean') {
 		return '';
@@ -81,6 +101,7 @@ function _renderToStringPretty(
 
 	if (Array.isArray(vnode)) {
 		let rendered = '';
+		parent[CHILDREN] = vnode;
 		for (let i = 0; i < vnode.length; i++) {
 			if (pretty && i > 0) rendered = rendered + '\n';
 			rendered =
@@ -91,7 +112,8 @@ function _renderToStringPretty(
 					opts,
 					inner,
 					isSvgMode,
-					selectValue
+					selectValue,
+					parent
 				);
 		}
 		return rendered;
@@ -100,6 +122,7 @@ function _renderToStringPretty(
 	// VNodes have {constructor:undefined} to prevent JSON injection:
 	if (vnode.constructor !== undefined) return '';
 
+	vnode[PARENT] = parent;
 	if (options[DIFF]) options[DIFF](vnode);
 
 	let nodeName = vnode.type,
@@ -124,7 +147,8 @@ function _renderToStringPretty(
 				opts,
 				opts.shallowHighOrder !== false,
 				isSvgMode,
-				selectValue
+				selectValue,
+				vnode
 			);
 		} else {
 			let rendered;
@@ -203,7 +227,8 @@ function _renderToStringPretty(
 				opts,
 				opts.shallowHighOrder !== false,
 				isSvgMode,
-				selectValue
+				selectValue,
+				vnode
 			);
 
 			if (options[DIFFED]) options[DIFFED](vnode);
@@ -384,7 +409,8 @@ function _renderToStringPretty(
 						opts,
 						true,
 						childSvgMode,
-						selectValue
+						selectValue,
+						vnode
 					);
 
 				if (shouldPrettyFormatChildren && !hasLarge && isLargeString(ret))

test/pretty.test.jsx

@@ -1,6 +1,7 @@
 import basicRender from '../src/index.js';
 import { render } from '../src/jsx.js';
 import { h, Fragment } from 'preact';
+import { useId } from 'preact/hooks';
 import { expect, describe, it } from 'vitest';
 import { dedent, svgAttributes, htmlAttributes } from './utils.jsx';
 
@@ -267,4 +268,60 @@ describe('pretty', () => {
 			}
 		});
 	});
+
+	describe('useId', () => {
+		it('should produce unique IDs for sibling components', () => {
+			function Foo() {
+				const id = useId();
+				return <div id={id} />;
+			}
+
+			const App = () => {
+				return (
+					<>
+						<Foo />
+						<Foo />
+					</>
+				);
+			};
+
+			const html = render(<App />);
+			// Each Foo component should have a unique ID
+			expect(html).to.contain('id="P0-0"');
+			expect(html).to.contain('id="P0-1"');
+		});
+
+		it('should produce unique IDs in nested components', () => {
+			function Child() {
+				const id = useId();
+				return <span id={id} />;
+			}
+
+			function Parent() {
+				const id = useId();
+				return (
+					<div id={id}>
+						<Child />
+					</div>
+				);
+			}
+
+			const App = () => {
+				return (
+					<>
+						<Parent />
+						<Parent />
+					</>
+				);
+			};
+
+			const html = render(<App />);
+			// Should have 4 unique IDs total (2 Parents + 2 Children)
+			const idMatches = html.match(/id="P0-\d+"/g);
+			expect(idMatches).to.have.length(4);
+			// All IDs should be unique
+			const uniqueIds = new Set(idMatches);
+			expect(uniqueIds.size).to.equal(4);
+		});
+	});
 });