feat: add Link component fallbackToMpa prop

Author: maiieul

packages/qwik-city/src/runtime/src/link-component.tsx

@@ -24,14 +24,22 @@ export const Link = component$<LinkProps>((props) => {
   const loc = useLocation();
   const originalHref = props.href;
   const anchorRef = useSignal<HTMLAnchorElement>();
+
   const {
     onClick$,
     prefetch: prefetchProp,
     reload,
     replaceState,
     scroll,
+    fallbackToMpa: fallbackToMpaProp,
     ...linkProps
   } = (() => props)();
+
+  // We need an RFC to assess whether or not we want to provide the ability to pass a number to customize the MPA fallback threshold.
+  // This depends on how well this feature is received in real projects, but also on what the threshold is based on: number of bundles needed to be preloaded for the next route, or the size of these bundles.
+  // In the future, we might be able to speed up SPA so much that falling back to MPA will never make sense.
+  const fallbackToMpa = untrack(() => Boolean(fallbackToMpaProp ?? true));
+
   const clientNavPath = untrack(() => getClientNavPath({ ...linkProps, reload }, loc));
   linkProps.href = clientNavPath || originalHref;
 
@@ -68,7 +76,9 @@ export const Link = component$<LinkProps>((props) => {
   const preventDefault = clientNavPath
     ? sync$((event: MouseEvent, target: HTMLAnchorElement) => {
         if (!(event.metaKey || event.ctrlKey || event.shiftKey || event.altKey)) {
-          setMpaFallbackHref(target.href);
+          if (fallbackToMpa) {
+            setMpaFallbackHref(target.href);
+          }
           event.preventDefault();
         }
       })
@@ -86,7 +96,9 @@ export const Link = component$<LinkProps>((props) => {
             await nav(elm.href, { forceReload: reload, replaceState, scroll });
             elm.removeAttribute('aria-pressed');
           }
-          setMpaFallbackHref(null);
+          if (fallbackToMpa) {
+            setMpaFallbackHref(null);
+          }
         }
       })
     : undefined;
@@ -168,4 +180,11 @@ export interface LinkProps extends AnchorAttributes {
   reload?: boolean;
   replaceState?: boolean;
   scroll?: boolean;
+
+  /**
+   * **Defaults to _true_.**
+   *
+   * Whether Qwik should fallback to MPA navigation if too many bundles are queued for preloading.
+   */
+  fallbackToMpa?: boolean;
 }