Add error message when rewriting to dynamic SSG page

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

@@ -297,6 +297,7 @@ export async function renderToHTML(
   const bodyTags = (...args: any) => callMiddleware('bodyTags', args)
   const htmlProps = (...args: any) => callMiddleware('htmlProps', args, true)
 
+  const didRewrite = (req as any)._nextDidRewrite
   const isFallback = !!query.__nextFallback
   delete query.__nextFallback
 
@@ -314,15 +315,21 @@ export async function renderToHTML(
 
   if (
     process.env.NODE_ENV !== 'production' &&
-    isAutoExport &&
+    (isAutoExport || isFallback) &&
     isDynamicRoute(pathname) &&
-    (req as any)._nextDidRewrite
+    didRewrite
   ) {
     // TODO: add err.sh when rewrites go stable
-    // Behavior might change before then (prefer SSR in this case)
+    // Behavior might change before then (prefer SSR in this case).
+    // If we decide to ship rewrites to the client we could solve this
+    // by running over the rewrites and getting the params.
     throw new Error(
-      `Rewrites don't support auto-exported dynamic pages yet. ` +
-        `Using this will cause the page to fail to parse the params on the client`
+      `Rewrites don't support${
+        isFallback ? ' ' : ' auto-exported '
+      }dynamic pages${isFallback ? ' with getStaticProps ' : ' '}yet. ` +
+        `Using this will cause the page to fail to parse the params on the client${
+          isFallback ? ' for the fallback page ' : ''
+        }`
     )
   }
 

test/integration/prerender/test/index.test.js

@@ -378,6 +378,14 @@ const runTests = (dev = false) => {
   })
 
   if (dev) {
+    it('should show error when rewriting to dynamic SSG page', async () => {
+      const item = Math.round(Math.random() * 100)
+      const html = await renderViaHTTP(appPort, `/some-rewrite/${item}`)
+      expect(html).toContain(
+        `Rewrites don't support dynamic pages with getStaticProps yet. Using this will cause the page to fail to parse the params on the client for the fallback page`
+      )
+    })
+
     it('should always call getStaticProps without caching in dev', async () => {
       const initialRes = await fetchViaHTTP(appPort, '/something')
       expect(initialRes.headers.get('cache-control')).toBeFalsy()
@@ -595,8 +603,27 @@ const runTests = (dev = false) => {
 }
 
 describe('SPR Prerender', () => {
+  afterAll(() => fs.remove(nextConfig))
+
   describe('dev mode', () => {
     beforeAll(async () => {
+      await fs.writeFile(
+        nextConfig,
+        `
+        module.exports = {
+          experimental: {
+            rewrites() {
+              return [
+                {
+                  source: "/some-rewrite/:item",
+                  destination: "/blog/post-:item"
+                }
+              ]
+            }
+          }
+        }
+      `
+      )
       appPort = await findPort()
       app = await launchApp(appDir, appPort, {
         onStderr: msg => {