LibHTTP+LibWeb+RequestServer: Move Fetch's HTTP header infra to LibHTTP

The end goal here is for LibHTTP to be the home of our RFC 9111 (HTTP
caching) implementation. We currently have one implementation in LibWeb
for our in-memory cache and another in RequestServer for our disk cache.

The implementations both largely revolve around interacting with HTTP
headers. But in LibWeb, we are using Fetch's header infra, and in RS we
are using are home-grown header infra from LibHTTP.

So to give these a common denominator, this patch replaces the LibHTTP
implementation with Fetch's infra. Our existing LibHTTP implementation
was not particularly compliant with any spec, so this at least gives us
a standards-based common implementation.

This migration also required moving a handful of other Fetch AOs over
to LibHTTP. (It turns out these AOs were all from the Fetch/Infra/HTTP
folder, so perhaps it makes sense for LibHTTP to be the implementation
of that entire set of facilities.)

Libraries/LibWeb/Fetch/Request.cpp

@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <LibHTTP/Method.h>
 #include <LibJS/Runtime/Completion.h>
 #include <LibWeb/Bindings/Intrinsics.h>
 #include <LibWeb/Bindings/RequestPrototype.h>
@@ -12,9 +13,7 @@
 #include <LibWeb/Fetch/Enums.h>
 #include <LibWeb/Fetch/Headers.h>
 #include <LibWeb/Fetch/Infrastructure/HTTP/Bodies.h>
-#include <LibWeb/Fetch/Infrastructure/HTTP/Headers.h>
 #include <LibWeb/Fetch/Infrastructure/HTTP/MIME.h>
-#include <LibWeb/Fetch/Infrastructure/HTTP/Methods.h>
 #include <LibWeb/Fetch/Infrastructure/HTTP/Requests.h>
 #include <LibWeb/Fetch/Request.h>
 #include <LibWeb/HTML/Scripting/Environments.h>
@@ -188,7 +187,7 @@ WebIDL::ExceptionOr<GC::Ref<Request>> Request::construct_impl(JS::Realm& realm,
 
     // header list
     //     A copy of request’s header list.
-    auto header_list_copy = Infrastructure::HeaderList::create(vm);
+    auto header_list_copy = HTTP::HeaderList::create();
     for (auto& header : *input_request->header_list())
         header_list_copy->append(header);
     request->set_header_list(header_list_copy);
@@ -370,13 +369,13 @@ WebIDL::ExceptionOr<GC::Ref<Request>> Request::construct_impl(JS::Realm& realm,
         auto method = *init.method;
 
         // 2. If method is not a method or method is a forbidden method, then throw a TypeError.
-        if (!Infrastructure::is_method(method))
+        if (!HTTP::is_method(method))
             return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Method has invalid value"sv };
-        if (Infrastructure::is_forbidden_method(method))
+        if (HTTP::is_forbidden_method(method))
             return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Method must not be one of CONNECT, TRACE, or TRACK"sv };
 
         // 3. Normalize method.
-        auto normalized_method = Infrastructure::normalize_method(method);
+        auto normalized_method = HTTP::normalize_method(method);
 
         // 4. Set request’s method to method.
         request->set_method(move(normalized_method));
@@ -410,7 +409,7 @@ WebIDL::ExceptionOr<GC::Ref<Request>> Request::construct_impl(JS::Realm& realm,
     // 32. If this’s request’s mode is "no-cors", then:
     if (request_object->request()->mode() == Infrastructure::Request::Mode::NoCORS) {
         // 1. If this’s request’s method is not a CORS-safelisted method, then throw a TypeError.
-        if (!Infrastructure::is_cors_safelisted_method(request_object->request()->method()))
+        if (!HTTP::is_cors_safelisted_method(request_object->request()->method()))
             return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Method must be one of GET, HEAD, or POST"sv };
 
         // 2. Set this’s headers’s guard to "request-no-cors".
@@ -420,24 +419,28 @@ WebIDL::ExceptionOr<GC::Ref<Request>> Request::construct_impl(JS::Realm& realm,
     // 33. If init is not empty, then:
     if (!init.is_empty()) {
         // 1. Let headers be a copy of this’s headers and its associated header list.
-        auto headers = Variant<HeadersInit, GC::Ref<Infrastructure::HeaderList>> { request_object->headers()->header_list() };
-
         // 2. If init["headers"] exists, then set headers to init["headers"].
-        if (init.headers.has_value())
-            headers = *init.headers;
+        auto headers = [&]() -> Variant<HeadersInit, NonnullRefPtr<HTTP::HeaderList>> {
+            if (init.headers.has_value())
+                return init.headers.value();
+            return HTTP::HeaderList::create(request_object->headers()->header_list()->headers());
+        }();
 
         // 3. Empty this’s headers’s header list.
         request_object->headers()->header_list()->clear();
 
-        // 4. If headers is a Headers object, then for each header of its header list, append header to this’s headers.
-        if (auto* header_list = headers.get_pointer<GC::Ref<Infrastructure::HeaderList>>()) {
-            for (auto& header : *header_list->ptr())
-                TRY(request_object->headers()->append(Infrastructure::Header::isomorphic_encode(header.name, header.value)));
-        }
-        // 5. Otherwise, fill this’s headers with headers.
-        else {
-            TRY(request_object->headers()->fill(headers.get<HeadersInit>()));
-        }
+        TRY(headers.visit(
+            // 4. If headers is a Headers object, then for each header of its header list, append header to this’s headers.
+            [&](NonnullRefPtr<HTTP::HeaderList> const& headers) -> WebIDL::ExceptionOr<void> {
+                for (auto const& header : *headers)
+                    TRY(request_object->headers()->append(HTTP::Header::isomorphic_encode(header.name, header.value)));
+                return {};
+            },
+            // 5. Otherwise, fill this’s headers with headers.
+            [&](HeadersInit const& headers) -> WebIDL::ExceptionOr<void> {
+                TRY(request_object->headers()->fill(headers));
+                return {};
+            }));
     }
 
     // 34. Let inputBody be input’s request’s body if input is a Request object; otherwise null.
@@ -465,7 +468,7 @@ WebIDL::ExceptionOr<GC::Ref<Request>> Request::construct_impl(JS::Realm& realm,
 
         // 4. If type is non-null and this’s headers’s header list does not contain `Content-Type`, then append (`Content-Type`, type) to this’s headers.
         if (type.has_value() && !request_object->headers()->header_list()->contains("Content-Type"sv))
-            TRY(request_object->headers()->append(Infrastructure::Header::isomorphic_encode("Content-Type"sv, *type)));
+            TRY(request_object->headers()->append(HTTP::Header::isomorphic_encode("Content-Type"sv, *type)));
     }
 
     // 38. Let inputOrInitBody be initBody if it is non-null; otherwise inputBody.