fix: keep ?fresh-partial an implementation detail

packages/fresh/src/runtime/client/partials.ts

@@ -83,7 +83,7 @@ if (!history.state) {
   history.replaceState(state, document.title);
 }
 
-function maybeUpdateHistory(nextUrl: URL) {
+function maybePushHistory(nextUrl: URL) {
   // Only add history entry when URL is new. Still apply
   // the partials because sometimes users click a link to
   // "refresh" the current page.
@@ -106,6 +106,12 @@ function maybeUpdateHistory(nextUrl: URL) {
   }
 }
 
+function maybeReplaceHistory(nextUrl: URL) {
+  if (nextUrl.href !== globalThis.location.href) {
+    history.replaceState(history.state, "", nextUrl.href);
+  }
+}
+
 document.addEventListener("click", async (e) => {
   let el = e.target;
   if (el && (el instanceof HTMLElement || el instanceof SVGElement)) {
@@ -154,7 +160,7 @@ document.addEventListener("click", async (e) => {
 
       const nextUrl = new URL(el.href);
       try {
-        maybeUpdateHistory(nextUrl);
+        maybePushHistory(nextUrl);
 
         const partialUrl = new URL(
           partial ? partial : nextUrl.href,
@@ -361,6 +367,7 @@ async function fetchPartials(
       actualUrl = nextUrl;
     }
   }
+  actualUrl.searchParams.delete(PARTIAL_SEARCH_PARAM);
 
   try {
     await applyPartials(res);
@@ -375,7 +382,7 @@ async function fetchPartials(
   }
 
   if (shouldNavigate) {
-    maybeUpdateHistory(actualUrl);
+    maybeReplaceHistory(actualUrl);
   }
 }
 

packages/fresh/tests/partials_test.tsx

@@ -3498,3 +3498,93 @@ Deno.test({
     });
   },
 });
+
+Deno.test({
+  name: "partials - redirect does not create back-button trap",
+  fn: async () => {
+    const app = testApp()
+      .get("/target", (ctx) => {
+        return ctx.render(
+          <Doc>
+            <Partial name="foo">
+              <h1 class="done">target page</h1>
+            </Partial>
+          </Doc>,
+        );
+      })
+      .get("/redirect", (ctx) => ctx.redirect("/target"))
+      .get("/", (ctx) => {
+        return ctx.render(
+          <Doc>
+            <div f-client-nav>
+              <a href="/redirect" class="nav">go</a>
+              <Partial name="foo">
+                <h1 class="init">home</h1>
+              </Partial>
+            </div>
+          </Doc>,
+        );
+      });
+
+    await withBrowserApp(app, async (page, address) => {
+      await page.goto(address, { waitUntil: "load" });
+      await page.locator(".init").wait();
+
+      // Click link that redirects
+      await page.locator(".nav").click();
+      await page.locator(".done").wait();
+
+      // Should show the redirect target URL, not the intermediate
+      await page.waitForFunction(() => {
+        return window.location.pathname === "/target";
+      });
+
+      // Going back should return to home, not to /redirect
+      await page.evaluate(() => window.history.go(-1));
+      await page.locator(".init").wait();
+      await page.waitForFunction(() => {
+        return window.location.pathname === "/";
+      });
+    });
+  },
+});
+
+Deno.test({
+  name: "partials - redirect does not leak ?fresh-partial in URL",
+  fn: async () => {
+    const app = testApp()
+      .get("/target", (ctx) => {
+        return ctx.render(
+          <Doc>
+            <Partial name="foo">
+              <h1 class="done">target page</h1>
+            </Partial>
+          </Doc>,
+        );
+      })
+      .get("/redirect", (ctx) => ctx.redirect("/target"))
+      .get("/", (ctx) => {
+        return ctx.render(
+          <Doc>
+            <div f-client-nav>
+              <a href="/redirect" class="nav">go</a>
+              <Partial name="foo">
+                <h1 class="init">home</h1>
+              </Partial>
+            </div>
+          </Doc>,
+        );
+      });
+
+    await withBrowserApp(app, async (page, address) => {
+      await page.goto(address, { waitUntil: "load" });
+      await page.locator(".init").wait();
+
+      await page.locator(".nav").click();
+      await page.locator(".done").wait();
+
+      const url = await page.evaluate(() => window.location.href);
+      expect(url).not.toContain("fresh-partial");
+    });
+  },
+});