Bug 1273255 - Don't try alternate URIs at the end of pageload if the channel was redirected: we don't want to be applying that sort of fixup to the redirect target URI. r=smaug

docshell/base/nsDocShell.cpp

@@ -7761,6 +7761,16 @@ nsDocShell::EndPageLoad(nsIWebProgress* aProgress,
               doCreateAlternate = false;
             }
           }
+
+          if (doCreateAlternate) {
+            // Skip doing this if our channel was redirected, because we
+            // shouldn't be guessing things about the post-redirect URI.
+            nsLoadFlags loadFlags = 0;
+            if (NS_FAILED(aChannel->GetLoadFlags(&loadFlags)) ||
+                (loadFlags & nsIChannel::LOAD_REPLACE)) {
+              doCreateAlternate = false;
+            }
+          }
         }
         if (doCreateAlternate) {
           newURI = nullptr;

docshell/test/browser/browser.ini

@@ -76,6 +76,9 @@ skip-if = buildapp == 'mulet'
 [browser_bug852909.js]
 [browser_bug92473.js]
 [browser_uriFixupIntegration.js]
+[browser_uriFixupAlternateRedirects.js]
+support-files =
+  redirect_to_example.sjs
 [browser_loadDisallowInherit.js]
 [browser_loadURI.js]
 [browser_multiple_pushState.js]

docshell/test/browser/browser_uriFixupAlternateRedirects.js

@@ -0,0 +1,24 @@
+"use strict";
+
+const REDIRECTURL = "http://www.example.com/browser/docshell/test/browser/redirect_to_example.sjs"
+
+add_task(function* () {
+  let tab = yield BrowserTestUtils.openNewForegroundTab(gBrowser, "about:blank");
+  gURLBar.value = REDIRECTURL;
+  gURLBar.select();
+  let errorPageLoaded = BrowserTestUtils.waitForErrorPage(tab.linkedBrowser);
+  EventUtils.sendKey("return");
+  yield errorPageLoaded;
+  let [contentURL, originalURL] = yield ContentTask.spawn(tab.linkedBrowser, null, () => {
+    return [
+      content.document.documentURI,
+      content.document.mozDocumentURIIfNotForErrorPages.spec,
+    ];
+  });
+  info("Page that loaded: " + contentURL);
+  ok(contentURL.startsWith("about:neterror?"), "Should be on an error page");
+  originalURL = new URL(originalURL);
+  is(originalURL.host, "example", "Should be an error for http://example, not http://www.example.com/");
+
+  yield BrowserTestUtils.removeTab(tab);
+});

docshell/test/browser/redirect_to_example.sjs

@@ -0,0 +1,4 @@
+function handleRequest(request, response) {
+  response.setStatusLine(request.httpVersion, 302, "Moved Permanently");
+  response.setHeader("Location", "http://example");
+}