Ignore functions passed as children

.changeset/curly-bananas-do.md

@@ -2,4 +2,4 @@
 'preact-render-to-string': patch
 ---
 
-Fix object children being rendered as `undefined`
+Fix object and function children being rendered as `undefined`

src/index.js

@@ -195,6 +195,7 @@ function _renderToString(vnode, context, isSvgMode, selectValue, parent) {
 
 	// Text VNodes: escape as HTML
 	if (typeof vnode !== 'object') {
+		if (typeof vnode === 'function') return '';
 		return encodeEntities(vnode);
 	}
 

src/pretty.js

@@ -29,6 +29,7 @@ export function _renderToStringPretty(
 
 	// #text nodes
 	if (typeof vnode !== 'object') {
+		if (typeof vnode === 'function') return '';
 		return encodeEntities(vnode);
 	}
 

test/jsx.test.js

@@ -167,4 +167,8 @@ describe('jsx', () => {
 	it('should prevent JSON injection', () => {
 		expect(renderJsx(<div>{{ hello: 'world' }}</div>)).to.equal('<div></div>');
 	});
+
+	it('should not render function children', () => {
+		expect(renderJsx(<div>{() => {}}</div>)).to.equal('<div></div>');
+	});
 });

test/pretty.test.js

@@ -228,4 +228,8 @@ describe('pretty', () => {
 			'<div></div>'
 		);
 	});
+
+	it('should not render function children', () => {
+		expect(prettyRender(<div>{() => {}}</div>)).to.equal('<div></div>');
+	});
 });

test/render.test.js

@@ -1264,4 +1264,8 @@ describe('render', () => {
 	it('should prevent JSON injection', () => {
 		expect(render(<div>{{ hello: 'world' }}</div>)).to.equal('<div></div>');
 	});
+
+	it('should not render function children', () => {
+		expect(render(<div>{() => {}}</div>)).to.equal('<div></div>');
+	});
 });