From 6e75440d5a73d44ecb0456550ab0aa483ca763ee Mon Sep 17 00:00:00 2001
From: Andrew Kaster <akaster@serenityos.org>
Date: Sun, 4 Feb 2024 03:41:07 -0700
Subject: [PATCH] LibWeb: Bring Document::fallback_base_url closer to the spec

---
 Userland/Libraries/LibWeb/DOM/Document.cpp        | 15 +++++++++++----
 .../Libraries/LibWeb/HTML/BrowsingContext.cpp     | 12 ++++++++++++
 Userland/Libraries/LibWeb/HTML/BrowsingContext.h  |  3 ++-
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/Userland/Libraries/LibWeb/DOM/Document.cpp b/Userland/Libraries/LibWeb/DOM/Document.cpp
index 3db7e97d52b..0082073eef7 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Document.cpp
@@ -910,11 +910,18 @@ JS::GCPtr<HTML::HTMLBaseElement const> Document::first_base_element_with_href_in
 // https://html.spec.whatwg.org/multipage/urls-and-fetching.html#fallback-base-url
 AK::URL Document::fallback_base_url() const
 {
-    // FIXME: 1. If document is an iframe srcdoc document, then return the document base URL of document's browsing context's container document.
+    // 1. If document is an iframe srcdoc document, then:
+    if (HTML::url_matches_about_srcdoc(m_url)) {
+        // 1. Assert: document's about base URL is non-null.
+        VERIFY(m_about_base_url.has_value());
 
-    // 2. If document's URL is about:blank, and document's browsing context's creator base URL is non-null, then return that creator base URL.
-    if (m_url == "about:blank"sv && browsing_context() && browsing_context()->creator_url().has_value())
-        return browsing_context()->creator_url().value();
+        // 2. Return document's about base URL.
+        return m_about_base_url.value();
+    }
+
+    // 2. If document's URL matches about:blank and document's about base URL is non-null, then return document's about base URL.
+    if (HTML::url_matches_about_blank(m_url) && m_about_base_url.has_value())
+        return m_about_base_url.value();
 
     // 3. Return document's URL.
     return m_url;
diff --git a/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp b/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp
index 76741dc9cbb..1d2650c99bf 100644
--- a/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp
+++ b/Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp
@@ -51,6 +51,18 @@ bool url_matches_about_blank(AK::URL const& url)
         && url.host().has<Empty>();
 }
 
+// https://html.spec.whatwg.org/multipage/urls-and-fetching.html#matches-about:srcdoc
+bool url_matches_about_srcdoc(AK::URL const& url)
+{
+    // A URL matches about:srcdoc if its scheme is "about", its path contains a single string "srcdoc", its query is null, its username and password are the empty string, and its host is null.
+    return url.scheme() == "about"sv
+        && url.serialize_path() == "srcdoc"sv
+        && !url.query().has_value()
+        && url.raw_username().is_empty()
+        && url.raw_password().is_empty()
+        && url.host().has<Empty>();
+}
+
 // https://html.spec.whatwg.org/multipage/document-sequences.html#determining-the-origin
 HTML::Origin determine_the_origin(AK::URL const& url, SandboxingFlagSet sandbox_flags, Optional<HTML::Origin> source_origin)
 {
diff --git a/Userland/Libraries/LibWeb/HTML/BrowsingContext.h b/Userland/Libraries/LibWeb/HTML/BrowsingContext.h
index 9f1407c4ca2..5e96971028e 100644
--- a/Userland/Libraries/LibWeb/HTML/BrowsingContext.h
+++ b/Userland/Libraries/LibWeb/HTML/BrowsingContext.h
@@ -236,7 +236,8 @@ HTML::Origin determine_the_origin(AK::URL const& url, SandboxingFlagSet sandbox_
 
 SandboxingFlagSet determine_the_creation_sandboxing_flags(BrowsingContext const&, JS::GCPtr<DOM::Element> embedder);
 
-// FIXME: Find a better home for this
+// FIXME: Find a better home for these
 bool url_matches_about_blank(AK::URL const& url);
+bool url_matches_about_srcdoc(AK::URL const& url);
 
 }