throw errors in tag renderers, catch them in page

then log and render error message.
also give page a className.

packages/docs/src/common/resolveDocs.ts

@@ -24,7 +24,7 @@ export function resolveDocs(componentName: string, key: React.Key) {
 
     const docsComponent = (ReactDocs as any as DocsMap)[componentName];
     if (docsComponent == null) {
-        console.error(`Unknown @reactDocs component: ${componentName}`);
+        throw new Error(`Unknown @reactDocs component: ${componentName}`);
     }
     return React.createElement(docsComponent, { key });
 }

packages/docs/src/common/resolveExample.tsx

@@ -73,7 +73,7 @@ export function resolveExample(exampleName: string, key: React.Key) {
 
     const { component, packageName } = getExample(exampleName, Examples);
     if (component == null) {
-        throw new Error(`Unknown example component: ${exampleName}`);
+        throw new Error(`Unknown @example component: ${exampleName}`);
     }
     const fileName = exampleName.charAt(0).toLowerCase() + exampleName.slice(1) + ".tsx";
     return <Example

packages/docs/src/components/page.tsx

@@ -13,14 +13,19 @@ export const Page: React.SFC<IPageProps> = ({ tagRenderers, page }) => {
     const pageContents = page.contents.map((node, i) => {
         if (typeof node === "string") {
             return <div className="docs-section" dangerouslySetInnerHTML={{ __html: node }} key={i} />;
-        } else {
+        }
+
+        // try rendering the tag,
+        try {
             const renderer = tagRenderers[node.tag];
             if (renderer === undefined) {
-                console.error("Unknown tag '@%s' in '%s'; please supply a renderer.", node.tag, page.reference);
-                return undefined;
+                throw new Error(`Unknown @tag: ${node.tag}`);
             }
             return renderer(node.value, i, page);
+        } catch (ex) {
+            console.error(ex.message);
+            return <h3><code>{ex.message}</code></h3>
         }
     });
-    return <div>{pageContents}</div>;
+    return <div className="docs-page">{pageContents}</div>;
 };