Improve page swap fallback

slhx-js/runtime/slhx.js

@@ -144,7 +144,10 @@
 
   async function navigateUrl(href, root, mode = "replace") {
     const response = await fetch(href, { headers: { "X-SLHX-Partial": "1", "Accept": "text/html" } });
-    await applyResponse(response, root);
+    if (!await applyResponse(response, root) && mode !== "none") {
+      location.href = href;
+      return;
+    }
     if (mode === "push") history.pushState({ slhx: true }, "", href);
     else if (mode === "replace") history.replaceState({ slhx: true }, "", href);
   }
@@ -152,15 +155,19 @@
   async function applyResponse(response, root) {
     if (response.redirected) {
       location.href = response.url;
-      return;
+      return false;
     }
     if (!compatibleFingerprint(response, root)) {
       location.reload();
-      return;
+      return false;
     }
     const type = response.headers.get("content-type") || "";
-    if (type.includes("text/html")) applyHtml(await response.text(), root, response.headers.get("x-slhx-title"));
-    else if (type.includes("application/slhx")) applyBatch(await response.arrayBuffer(), root);
+    if (type.includes("text/html")) return applyHtml(await response.text(), root, response.headers.get("x-slhx-title"));
+    if (type.includes("application/slhx")) {
+      applyBatch(await response.arrayBuffer(), root);
+      return true;
+    }
+    return false;
   }
 
   function compatibleFingerprint(response, root) {
@@ -335,12 +342,13 @@
     const doc = new DOMParser().parseFromString(html, "text/html");
     const template = doc.querySelector("template[data-slhx]");
     if (!replaceSlot(scope, doc, "content", template ? template.innerHTML : html)) {
-      location.reload();
-      return;
+      emit(scope, "slhx:missing-content-slot", null);
+      return false;
     }
     replaceSlot(scope, doc, "nav");
     const nextTitle = title || (doc.querySelector("title") && doc.querySelector("title").textContent);
     if (nextTitle) document.title = nextTitle;
+    return true;
   }
 
   function replaceSlot(scope, doc, name, fallback) {