LibWeb: Consistently use the EmptyString state of ReferrerPolicy

We previously used an empty optional to denote that a ReferrerPolicy is
in the default empty string state. However, later additions added an
explicit EmptyString state. This patch moves all users to the explicit
state, and stops using `Optional<ReferrerPolicy>` everywhere except for
when an option not being passed from JavaScript has meaning.

Userland/Libraries/LibWeb/Fetch/Enums.cpp

@@ -23,11 +23,11 @@ namespace Web::Fetch {
 // - Fetch has use-cases beyond its JS interface, so having to refer to the 'Bindings' namespace
 //   constantly is irritating.
 
-Optional<ReferrerPolicy::ReferrerPolicy> from_bindings_enum(Bindings::ReferrerPolicy referrer_policy)
+ReferrerPolicy::ReferrerPolicy from_bindings_enum(Bindings::ReferrerPolicy referrer_policy)
 {
     switch (referrer_policy) {
     case Bindings::ReferrerPolicy::Empty:
-        return {};
+        return ReferrerPolicy::ReferrerPolicy::EmptyString;
     case Bindings::ReferrerPolicy::NoReferrer:
         return ReferrerPolicy::ReferrerPolicy::NoReferrer;
     case Bindings::ReferrerPolicy::NoReferrerWhenDowngrade:
@@ -113,11 +113,11 @@ Infrastructure::Request::RedirectMode from_bindings_enum(Bindings::RequestRedire
     }
 }
 
-Bindings::ReferrerPolicy to_bindings_enum(Optional<ReferrerPolicy::ReferrerPolicy> const& referrer_policy)
+Bindings::ReferrerPolicy to_bindings_enum(ReferrerPolicy::ReferrerPolicy referrer_policy)
 {
-    if (!referrer_policy.has_value())
+    switch (referrer_policy) {
+    case ReferrerPolicy::ReferrerPolicy::EmptyString:
         return Bindings::ReferrerPolicy::Empty;
-    switch (*referrer_policy) {
     case ReferrerPolicy::ReferrerPolicy::NoReferrer:
         return Bindings::ReferrerPolicy::NoReferrer;
     case ReferrerPolicy::ReferrerPolicy::NoReferrerWhenDowngrade:

Userland/Libraries/LibWeb/Fetch/Enums.h

@@ -13,13 +13,13 @@
 
 namespace Web::Fetch {
 
-[[nodiscard]] Optional<ReferrerPolicy::ReferrerPolicy> from_bindings_enum(Bindings::ReferrerPolicy);
+[[nodiscard]] ReferrerPolicy::ReferrerPolicy from_bindings_enum(Bindings::ReferrerPolicy);
 [[nodiscard]] Infrastructure::Request::Mode from_bindings_enum(Bindings::RequestMode);
 [[nodiscard]] Infrastructure::Request::CredentialsMode from_bindings_enum(Bindings::RequestCredentials);
 [[nodiscard]] Infrastructure::Request::CacheMode from_bindings_enum(Bindings::RequestCache);
 [[nodiscard]] Infrastructure::Request::RedirectMode from_bindings_enum(Bindings::RequestRedirect);
 
-[[nodiscard]] Bindings::ReferrerPolicy to_bindings_enum(Optional<ReferrerPolicy::ReferrerPolicy> const&);
+[[nodiscard]] Bindings::ReferrerPolicy to_bindings_enum(ReferrerPolicy::ReferrerPolicy);
 [[nodiscard]] Bindings::RequestDestination to_bindings_enum(Optional<Infrastructure::Request::Destination> const&);
 [[nodiscard]] Bindings::RequestMode to_bindings_enum(Infrastructure::Request::Mode);
 [[nodiscard]] Bindings::RequestCredentials to_bindings_enum(Infrastructure::Request::CredentialsMode);

Userland/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp

@@ -236,7 +236,7 @@ WebIDL::ExceptionOr<Optional<JS::NonnullGCPtr<PendingResponse>>> main_fetch(JS::
 
     // 8. If request’s referrer policy is the empty string, then set request’s referrer policy to request’s policy
     //    container’s referrer policy.
-    if (!request->referrer_policy().has_value()) {
+    if (request->referrer_policy() == ReferrerPolicy::ReferrerPolicy::EmptyString) {
         VERIFY(request->policy_container().has<HTML::PolicyContainer>());
         request->set_referrer_policy(request->policy_container().get<HTML::PolicyContainer>().referrer_policy);
     }

Userland/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Requests.cpp

@@ -309,8 +309,8 @@ ErrorOr<void> Request::add_origin_header()
     // 3. Otherwise, if request’s method is neither `GET` nor `HEAD`, then:
     else if (!StringView { m_method }.is_one_of("GET"sv, "HEAD"sv)) {
         // 1. If request’s mode is not "cors", then switch on request’s referrer policy:
-        if (m_mode != Mode::CORS && m_referrer_policy.has_value()) {
-            switch (*m_referrer_policy) {
+        if (m_mode != Mode::CORS) {
+            switch (m_referrer_policy) {
             // -> "no-referrer"
             case ReferrerPolicy::ReferrerPolicy::NoReferrer:
                 // Set serializedOrigin to `null`.

Userland/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Requests.h

@@ -273,8 +273,8 @@ public:
     [[nodiscard]] ReferrerType const& referrer() const { return m_referrer; }
     void set_referrer(ReferrerType referrer) { m_referrer = move(referrer); }
 
-    [[nodiscard]] Optional<ReferrerPolicy::ReferrerPolicy> const& referrer_policy() const { return m_referrer_policy; }
-    void set_referrer_policy(Optional<ReferrerPolicy::ReferrerPolicy> referrer_policy) { m_referrer_policy = move(referrer_policy); }
+    [[nodiscard]] ReferrerPolicy::ReferrerPolicy const& referrer_policy() const { return m_referrer_policy; }
+    void set_referrer_policy(ReferrerPolicy::ReferrerPolicy referrer_policy) { m_referrer_policy = move(referrer_policy); }
 
     [[nodiscard]] ResponseTainting response_tainting() const { return m_response_tainting; }
     void set_response_tainting(ResponseTainting response_tainting) { m_response_tainting = response_tainting; }
@@ -420,7 +420,7 @@ private:
     // https://fetch.spec.whatwg.org/#concept-request-referrer-policy
     // A request has an associated referrer policy, which is a referrer policy. Unless stated otherwise it is the empty
     // string.
-    Optional<ReferrerPolicy::ReferrerPolicy> m_referrer_policy;
+    ReferrerPolicy::ReferrerPolicy m_referrer_policy { ReferrerPolicy::ReferrerPolicy::EmptyString };
 
     // https://fetch.spec.whatwg.org/#concept-request-mode
     // A request has an associated mode, which is "same-origin", "cors", "no-cors", "navigate", or "websocket". Unless

Userland/Libraries/LibWeb/HTML/HTMLImageElement.cpp

@@ -559,7 +559,7 @@ after_step_7:
             request->set_initiator(Fetch::Infrastructure::Request::Initiator::ImageSet);
 
         // 21. Set request's referrer policy to the current state of the element's referrerpolicy attribute.
-        request->set_referrer_policy(ReferrerPolicy::from_string(get_attribute_value(HTML::AttributeNames::referrerpolicy)));
+        request->set_referrer_policy(ReferrerPolicy::from_string(get_attribute_value(HTML::AttributeNames::referrerpolicy)).value_or(ReferrerPolicy::ReferrerPolicy::EmptyString));
 
         // FIXME: 22. Set request's priority to the current state of the element's fetchpriority attribute.
 
@@ -774,7 +774,7 @@ void HTMLImageElement::react_to_changes_in_the_environment()
         request->set_initiator(Fetch::Infrastructure::Request::Initiator::ImageSet);
 
         // 3. Set request's referrer policy to the current state of the element's referrerpolicy attribute.
-        request->set_referrer_policy(ReferrerPolicy::from_string(get_attribute_value(HTML::AttributeNames::referrerpolicy)));
+        request->set_referrer_policy(ReferrerPolicy::from_string(get_attribute_value(HTML::AttributeNames::referrerpolicy)).value_or(ReferrerPolicy::ReferrerPolicy::EmptyString));
 
         // FIXME: 4. Set request's priority to the current state of the element's fetchpriority attribute.
 

Userland/Libraries/LibWeb/HTML/HTMLLinkElement.h

@@ -70,7 +70,7 @@ private:
         CORSSettingAttribute crossorigin { CORSSettingAttribute::NoCORS };
         // referrer policy (default the empty string)
         //      A referrer policy
-        Optional<ReferrerPolicy::ReferrerPolicy> referrer_policy {};
+        ReferrerPolicy::ReferrerPolicy referrer_policy { ReferrerPolicy::ReferrerPolicy::EmptyString };
         // FIXME: source set (default null)
         //          Null or a source set
         // base URL

Userland/Libraries/LibWeb/HTML/HTMLScriptElement.cpp

@@ -54,10 +54,7 @@ void HTMLScriptElement::attribute_changed(FlyString const& name, Optional<String
     if (name == HTML::AttributeNames::crossorigin) {
         m_crossorigin = cors_setting_attribute_from_keyword(value);
     } else if (name == HTML::AttributeNames::referrerpolicy) {
-        if (!value.has_value())
-            m_referrer_policy.clear();
-        else
-            m_referrer_policy = ReferrerPolicy::from_string(*value);
+        m_referrer_policy = ReferrerPolicy::from_string(value.value_or(""_string)).value_or(ReferrerPolicy::ReferrerPolicy::EmptyString);
     }
 }
 

Userland/Libraries/LibWeb/HTML/HTMLScriptElement.h

@@ -107,7 +107,7 @@ private:
     CORSSettingAttribute m_crossorigin { CORSSettingAttribute::NoCORS };
 
     // https://html.spec.whatwg.org/multipage/scripting.html#attr-script-referrerpolicy
-    Optional<ReferrerPolicy::ReferrerPolicy> m_referrer_policy;
+    ReferrerPolicy::ReferrerPolicy m_referrer_policy { ReferrerPolicy::ReferrerPolicy::EmptyString };
 
     bool m_failed_to_load { false };
 

Userland/Libraries/LibWeb/HTML/Scripting/Fetching.h

@@ -42,7 +42,7 @@ struct ScriptFetchOptions {
     Fetch::Infrastructure::Request::CredentialsMode credentials_mode { Fetch::Infrastructure::Request::CredentialsMode::SameOrigin };
 
     // https://html.spec.whatwg.org/multipage/webappapis.html#concept-script-fetch-options-referrer-policy
-    Optional<ReferrerPolicy::ReferrerPolicy> referrer_policy;
+    ReferrerPolicy::ReferrerPolicy referrer_policy { ReferrerPolicy::ReferrerPolicy::EmptyString };
 
     // https://html.spec.whatwg.org/multipage/webappapis.html#concept-script-fetch-options-render-blocking
     bool render_blocking { false };

Userland/Libraries/LibWeb/ReferrerPolicy/AbstractOperations.cpp

@@ -82,8 +82,8 @@ Optional<URL> determine_requests_referrer(Fetch::Infrastructure::Request const&
 
     // 8. Execute the statements corresponding to the value of policy:
     // Note: If request’s referrer policy is the empty string, Fetch will not call into this algorithm.
-    VERIFY(policy.has_value());
-    switch (*policy) {
+    VERIFY(policy != ReferrerPolicy::EmptyString);
+    switch (policy) {
     // "no-referrer"
     case ReferrerPolicy::NoReferrer:
         // Return no referrer

Userland/Libraries/LibWeb/ReferrerPolicy/ReferrerPolicy.cpp

@@ -35,6 +35,8 @@ StringView to_string(ReferrerPolicy referrer_policy)
 
 Optional<ReferrerPolicy> from_string(StringView string)
 {
+    if (string.is_empty())
+        return ReferrerPolicy::EmptyString;
     if (string.equals_ignoring_ascii_case("no-referrer"sv))
         return ReferrerPolicy::NoReferrer;
     if (string.equals_ignoring_ascii_case("no-referrer-when-downgrade"sv))