Add err.sh for getStaticProps error

errors/invalid-getstaticprops-value.md

@@ -0,0 +1,17 @@
+# Invalid unstable_getStaticProps Return Value
+
+#### Why This Error Occurred
+
+In one of the page's `unstable_getStaticProps` the return value had the incorrect shape.
+
+#### Possible Ways to Fix It
+
+Make sure to return the following shape from `unstable_getStaticProps`:
+
+```js
+export async function unstable_getStaticProps() {
+  return {
+    props: { [key: string]: any }
+  }
+}
+```

packages/next/next-server/server/render.tsx

@@ -246,7 +246,8 @@ const invalidKeysMsg = (methodName: string, invalidKeys: string[]) => {
   return (
     `Additional keys were returned from \`${methodName}\`. Properties intended for your component must be nested under the \`props\` key, e.g.:` +
     `\n\n\treturn { props: { title: 'My Title', content: '...' } }` +
-    `\n\nKeys that need to be moved: ${invalidKeys.join(', ')}.`
+    `\n\nKeys that need to be moved: ${invalidKeys.join(', ')}.` +
+    `See here for more info: https://err.sh/zeit/next.js/invalid-getstaticprops-value`
   )
 }