feat: fail the build for dynamic fs-routes without generateStaticParams

packages/docs/src/pages/learn/FileSystemRouting.mdx

@@ -120,9 +120,9 @@ export default function BlogPost({ params }: { params: { slug: string } }) {
 
 This generates `blog/hello.html` and `blog/world.html`. Each page component receives the resolved `params` as a prop.
 
-A dynamic route without `generateStaticParams` is **not** pre-rendered (a warning is logged); it still resolves on the client via the SPA fallback.
+A dynamic route **must** export `generateStaticParams`; the build fails otherwise. A static site can only serve pages that were enumerated at build time, so a dynamic route without it would produce no output.
 
-> **Note:** Because static hosting serves one pre-rendered RSC payload per page, soft client-side navigation between different values of the _same_ dynamic route reflects the params of the initially-loaded page. Loading a dynamic URL directly (or via the SPA fallback) always renders the correct params. Static routes and layouts navigate fully on the client.
+> **Note:** Because static hosting serves one pre-rendered RSC payload per page, soft client-side navigation between different values of the _same_ dynamic route reflects the params of the initially-loaded page. Loading a dynamic URL directly always renders the correct params. Static routes and layouts navigate fully on the client.
 
 ## Custom Conventions (Adapters)
 

packages/static/src/fs-routes/runtime.tsx

@@ -115,7 +115,7 @@ export function createFsRoutesEntries(
     };
     const files = modulesToRouteFiles(modules, warn);
     const tree = adapter.buildRoutes(files);
-    const pages = await collectStaticPaths(tree, warn);
+    const pages = await collectStaticPaths(tree);
     for (const { urlPath, params } of pages) {
       yield {
         path: urlPathToFilePath(urlPath),

packages/static/src/fs-routes/tree.test.ts

@@ -94,15 +94,13 @@ describe("collectStaticPaths", () => {
     ]);
   });
 
-  it("warns and skips a dynamic route without generateStaticParams", async () => {
+  it("throws for a dynamic route without generateStaticParams", async () => {
     const tree: FsRouteTreeNode[] = [
       { path: "/blog/:slug", page: true, module: component },
     ];
-    const warn = vi.fn();
-    const pages = await collectStaticPaths(tree, warn);
-    expect(pages).toEqual([]);
-    expect(warn).toHaveBeenCalledTimes(1);
-    expect(warn.mock.calls[0]?.[0]).toContain("/blog/:slug");
+    await expect(collectStaticPaths(tree)).rejects.toThrow(
+      /"\/blog\/:slug".*generateStaticParams/,
+    );
   });
 
   it("throws when generateStaticParams is missing a param value", async () => {

packages/static/src/fs-routes/tree.ts

@@ -87,7 +87,6 @@ async function addPagesForLeaf(
   segments: string[],
   module: FsRouteModule,
   pages: StaticPage[],
-  onWarn?: (message: string) => void,
 ): Promise<void> {
   const dynamicSegments = segments.filter(isDynamicSegment);
 
@@ -98,11 +97,11 @@ async function addPagesForLeaf(
 
   const generate = module.generateStaticParams;
   if (typeof generate !== "function") {
-    onWarn?.(
-      `Dynamic route "${segmentsToUrl(segments)}" has no generateStaticParams() export; skipping static generation. ` +
-        `It will still work on the client via the SPA fallback.`,
+    throw new Error(
+      `Dynamic route "${segmentsToUrl(segments)}" has no generateStaticParams() export. ` +
+        `Every page of a static site must be enumerated at build time; ` +
+        `export generateStaticParams() from the page module to list the params to pre-render.`,
     );
-    return;
   }
 
   const paramSets = await generate();
@@ -126,17 +125,16 @@ async function walk(
   nodes: FsRouteTreeNode[],
   prefixSegments: string[],
   pages: StaticPage[],
-  onWarn?: (message: string) => void,
 ): Promise<void> {
   for (const node of nodes) {
     const ownSegments =
       node.path !== undefined ? splitRoutePath(node.path) : [];
     const segments = [...prefixSegments, ...ownSegments];
     if (node.page) {
-      await addPagesForLeaf(segments, node.module, pages, onWarn);
+      await addPagesForLeaf(segments, node.module, pages);
     }
     if (node.children) {
-      await walk(node.children, segments, pages, onWarn);
+      await walk(node.children, segments, pages);
     }
   }
 }
@@ -146,15 +144,15 @@ async function walk(
  *
  * Static routes are emitted directly. Dynamic routes (with `:param` or
  * catch-all segments) are expanded using each page module's
- * `generateStaticParams()`; if absent, the route is skipped and `onWarn` is
- * invoked.
+ * `generateStaticParams()`; a dynamic route without that export fails the
+ * build, since a static site cannot serve pages that were not enumerated at
+ * build time.
  */
 export async function collectStaticPaths(
   tree: FsRouteTreeNode[],
-  onWarn?: (message: string) => void,
 ): Promise<StaticPage[]> {
   const pages: StaticPage[] = [];
-  await walk(tree, [], pages, onWarn);
+  await walk(tree, [], pages);
   return pages;
 }
 

packages/static/src/fs-routes/types.ts

@@ -13,14 +13,13 @@ export interface FsRouteModule {
   /** The component for this page or layout. */
   default?: ComponentType<{ params: Record<string, string> }> | ComponentType;
   /**
-   * Optional function used to statically generate a dynamic route.
+   * Function used to statically generate a dynamic route. Required for pages
+   * whose route contains a dynamic segment; the build fails without it, since
+   * a static site cannot serve pages that were not enumerated at build time.
    *
    * Returns the list of concrete params to pre-render. Each entry maps every
    * dynamic param name in the route's path to a concrete string value. For a
    * catch-all segment, the value may contain slashes.
-   *
-   * Without this export, a dynamic route is not pre-rendered to HTML (it still
-   * works on the client via the SPA fallback).
    */
   generateStaticParams?: () => MaybePromise<Array<Record<string, string>>>;
   [key: string]: unknown;