[robobun]

Problem

• A route handler asks uWS for the method name and looks it up in METHOD_MAP. 12 readers handle a failed lookup. 10 of them substitute GET, POST or OPTIONS (RequestContext.rs:1426, DevServer.rs:1774).
• With Bun.serve: answer 501 to an unknown method and 404 to a router miss, not a closed socket #45396 and Bun.serve http3: 501 or 400 before the router for a request line the HTTP/2 listener refuses #45357 no handler runs for a name that is not in the map, so the arms cannot run.

Fix

• Request::method() returns a Method. The shim asks uWS for the id of the method (uws_req_get_method_id).
• The 12 arms go, and the Option<Method> parameters with them. So do Method::find(), RouteMethod::specific() and the string fallback in NodeHTTP.cpp.
• An id that is no Method fails a debug assertion. A release build reads it as GET, as before.
• Self-reviewed: 33 concerns raised, 32 addressed (Bun.serve: answer 501 to an unknown method and 404 to a router miss, not a closed socket #45396).

Behaviour change: none

Tests that cover this code: test/js/bun/http/bun-serve-routes.test.ts (each of the 36 methods must arrive as req.method), test/js/node/http/node-http.test.ts, test/js/bun/http/serve-http2.test.ts, test/js/bun/http/serve-http3.test.ts, test/js/bun/http/bun-serve-file.test.ts.

Background

• methodIdFromWire() (uws: resolve a request method to its id inline #44510) maps a method name to the discriminant of Method.
• Each transport answers a method with no id before a handler: 501 on HTTP/1.1 (Bun.serve: answer 501 to an unknown method and 404 to a router miss, not a closed socket #45396), HTTP/2 (Bun.serve http2: reject the request bytes the HTTP/1 parser rejects #40676) and HTTP/3 (Bun.serve http3: 501 or 400 before the router for a request line the HTTP/2 listener refuses #45357), 400 from the node:http parser.
• Considered an unchecked conversion of the id. Method::from_repr costs one compare.

Downsides

• Draft until Bun.serve http3: 501 or 400 before the router for a request line the HTTP/2 listener refuses #45357 lands. Without its HTTP/3 check an unknown :method reaches a handler: a debug build fails the assertion, and PatCh arrives as GET, not PATCH.
• Per request: the shim resolves the id (17 instructions for GET), and Method::which (22 for GET) goes. Release binary: 8,704 bytes smaller.

Notes

• The 12 arms: RequestContext.rs:1426, StaticRoute.rs:292, FileRoute.rs:233, DirectoryRoute.rs:107 and DevServer.rs:2129 (GET). DevServer.rs:1774 and :2099 (POST). mod.rs:758, server_body.rs:2904 and NodeHTTPResponse.rs:2751 (OPTIONS, for the body length). mod.rs:1315 passed undefined to C++, which then made a string from the name (NodeHTTP.cpp:96). HTMLBundle.rs:276 answered 405.
• Four functions lose their method parameter and read it from the request: prepare_js_request_context, prepare_js_request_context_for, prepare_and_save_js_request_context and upgrade_web_socket_user_route. RequestContext::create and create_in take a Method.
• RouteMethod::specific() gave the method of a route to its handler. It was always the method of the request: the HEAD that Bun derives from a GET route is registered as a HEAD route.
• Why no handler runs for a request without an id: the Bun.serve HTTP/1.1 dispatch answers 501 first (Bun.serve: answer 501 to an unknown method and 404 to a router miss, not a closed socket #45396), HTTP/2 does since Bun.serve http2: reject the request bytes the HTTP/1 parser rejects #40676, HTTP/3 does with Bun.serve http3: 501 or 400 before the router for a request line the HTTP/2 listener refuses #45357, and the parser of the node:http instantiation answers 400 (Bun.serve: answer 501 to an unknown method and 404 to a router miss, not a closed socket #45396 made that check part of the instantiation).
• This PR is a draft until Bun.serve http3: 501 or 400 before the router for a request line the HTTP/2 listener refuses #45357 lands. On HTTP/3 main lowercases the method for the lookup, so PatCh arrives as PATCH and BREW as GET. With this PR and no HTTP/3 check both arrive as GET in a release build, and a debug build fails the assertion.
• Before it leaves draft this branch needs a rebase: bake: move the code into folders by job (no behavior change) #45489 moved DevServer.rs into dev_server/, and three of the removed arms are there.
• Open question before this PR leaves draft: the first ask of Custom HTTP methods via Bun.serve() #6556, a method outside the 36 that reaches fetch. fetch, Request, server.fetch: stop sending GET for a method outside the method table #44718 (open) lets a Request carry any method token. This PR and uws: key HttpRouter by method id #45400 remove the method name from the path between uWS and Rust, so a request with no method id has no name to deliver. If maintainers want such a request delivered, the name must stay readable for it. That needs a maintainer decision.
• A release build reads an id that is no Method as GET. That is what each of the 10 arms did. uws: key HttpRouter by method id #45400 makes the router refuse such an id, and then Request::method() asserts it in release builds too.
• Instructions per request. In uWS (standalone driver over the real HttpParser.h and HttpRouter.h, clang -O3, qemu-x86_64 -one-insn-per-tb -d exec,nochain), node:http: keep the method of a dispatched request as sent in 'clientError' rawPacket #45398 then this PR: GET 2395, 2412. POST 2697, 2710. The 17 and 13 more are methodIdFromWire() in the shim. In Rust, Method::which goes: 31 instructions per call for GET and 30 for POST in a loop whose empty body costs 9 and 5 (cargo build --release of an example that calls it, same counter). The slice that the old shim returned goes too and is not counted.
• Instructions per request end to end: not measured. perf is not available in the build container (perf_event_paranoid is 4), and valgrind is not installed.
• sizeof: no struct changes.
• Release binary (llvm-size): text 80,701,779 -> 80,693,075 bytes (node:http: keep the method of a dispatched request as sent in 'clientError' rawPacket #45398, then this PR, on base f4d755a; measured before the two id getters moved into this PR). data and bss do not change.
• Suites (debug build with ASAN). On this PR: bun-serve-routes (86 tests), node-http-pipeline-callbacks, node-http, serve-http2, serve-http2-protocol, serve-http3, bun-serve-static, bun-serve-file, serve-directory-routes, bun-serve-html. On uws: key HttpRouter by method id #45400, which has this change: also node-http-displaced-response, request-smuggling, three test-http-*-client-error Node tests, and serve.test.ts.

[robobun]

Status

This PR changes no behaviour once #45357 is in. It is a draft until then. #45396 has the reproduction of the bug that this stack fixes.

The stack: #44510, #45396, #45397, #45398, #45399 (draft), #45400 (draft).