1 files changed, 110 insertions, 0 deletions
diff --git a/packages/integrations/preact/server.js b/packages/integrations/preact/server.js
new file mode 100644
index 000000000..f5b1a34e5
--- /dev/null
+++ b/packages/integrations/preact/server.js
@@ -0,0 +1,110 @@
+import { h, Component as BaseComponent } from 'preact';
+import render from 'preact-render-to-string';
+import StaticHtml from './static-html.js';
+
+const slotName = (str) => str.trim().replace(/[-_]([a-z])/g, (_, w) => w.toUpperCase());
+
+let originalConsoleError;
+let consoleFilterRefs = 0;
+
+function check(Component, props, children) {
+	if (typeof Component !== 'function') return false;
+
+	if (Component.prototype != null && typeof Component.prototype.render === 'function') {
+		return BaseComponent.isPrototypeOf(Component);
+	}
+
+	useConsoleFilter();
+
+	try {
+		try {
+			const { html } = renderToStaticMarkup(Component, props, children);
+			if (typeof html !== 'string') {
+				return false;
+			}
+
+			// There are edge cases (SolidJS) where Preact *might* render a string,
+			// but components would be <undefined></undefined>
+
+			return !/\<undefined\>/.test(html);
+		} catch (err) {
+			return false;
+		}
+	} finally {
+		finishUsingConsoleFilter();
+	}
+}
+
+function renderToStaticMarkup(Component, props, { default: children, ...slotted }) {
+	const slots = {};
+	for (const [key, value] of Object.entries(slotted)) {
+		const name = slotName(key);
+		slots[name] = h(StaticHtml, { value, name });
+	}
+	// Note: create newProps to avoid mutating `props` before they are serialized
+	const newProps = { ...props, ...slots };
+	const html = render(
+		h(Component, newProps, children != null ? h(StaticHtml, { value: children }) : children)
+	);
+	return { html };
+}
+
+/**
+ * Reduces console noise by filtering known non-problematic errors.
+ *
+ * Performs reference counting to allow parallel usage from async code.
+ *
+ * To stop filtering, please ensure that there always is a matching call
+ * to `finishUsingConsoleFilter` afterwards.
+ */
+function useConsoleFilter() {
+	consoleFilterRefs++;
+
+	if (!originalConsoleError) {
+		// eslint-disable-next-line no-console
+		originalConsoleError = console.error;
+
+		try {
+			// eslint-disable-next-line no-console
+			console.error = filteredConsoleError;
+		} catch (error) {
+			// If we're unable to hook `console.error`, just accept it
+		}
+	}
+}
+
+/**
+ * Indicates that the filter installed by `useConsoleFilter`
+ * is no longer needed by the calling code.
+ */
+function finishUsingConsoleFilter() {
+	consoleFilterRefs--;
+
+	// Note: Instead of reverting `console.error` back to the original
+	// when the reference counter reaches 0, we leave our hook installed
+	// to prevent potential race conditions once `check` is made async
+}
+
+/**
+ * Hook/wrapper function for the global `console.error` function.
+ *
+ * Ignores known non-problematic errors while any code is using the console filter.
+ * Otherwise, simply forwards all arguments to the original function.
+ */
+function filteredConsoleError(msg, ...rest) {
+	if (consoleFilterRefs > 0 && typeof msg === 'string') {
+		// In `check`, we attempt to render JSX components through Preact.
+		// When attempting this on a React component, React may output
+		// the following error, which we can safely filter out:
+		const isKnownReactHookError =
+			msg.includes('Warning: Invalid hook call.') &&
+			msg.includes('https://reactjs.org/link/invalid-hook-call');
+		if (isKnownReactHookError) return;
+	}
+	originalConsoleError(msg, ...rest);
+}
+
+export default {
+	check,
+	renderToStaticMarkup,
+};