Allow GET requests with bodies in entry worker (#677)

Whilst prohibited by the `Request` API spec, `GET` requests are
allowed to have bodies. If `Content-Length` or `Transfer-Encoding`
are specified, `workerd` will give the request a (potentially empty)
body. Passing a bodied-GET-request through to the `new Request()`
constructor should throw, but `workerd` has special handling to allow
this if a `Request` instance is passed.

Miniflare was previously decomposing the request before passing it
back to the `new Request()` constructor, defeating this detection.
This change ensures we always pass full `Request` instances to the
`new Request()` constructor in the entry worker.

Closes cloudflare/workerd#1122

packages/miniflare/src/workers/core/entry.worker.ts

@@ -46,13 +46,18 @@ function getUserRequest(
     url = new URL(path, upstreamUrl);
   }
 
-  request = new Request(url, {
-    method: request.method,
-    headers: request.headers,
-    cf: request.cf ?? env[CoreBindings.JSON_CF_BLOB],
-    redirect: request.redirect,
-    body: request.body,
-  });
+  // Note when constructing new `Request`s from `request`, we must always pass
+  // `request` as is to the `new Request()` constructor. Whilst prohibited by
+  // the `Request` API spec, `GET` requests are allowed to have bodies. If
+  // `Content-Length` or `Transfer-Encoding` are specified, `workerd` will give
+  // the request a (potentially empty) body. Passing a bodied-GET-request
+  // through to the `new Request()` constructor should throw, but `workerd` has
+  // special handling to allow this if a `Request` instance is passed.
+  // See https://github.com/cloudflare/workerd/issues/1122 for more details.
+  request = new Request(url, request);
+  if (request.cf === undefined) {
+    request = new Request(request, { cf: env[CoreBindings.JSON_CF_BLOB] });
+  }
   request.headers.delete(CoreHeaders.ORIGINAL_URL);
   return request;
 }

packages/miniflare/test/index.spec.ts

@@ -6,6 +6,7 @@ import http from "http";
 import { AddressInfo } from "net";
 import path from "path";
 import { Writable } from "stream";
+import { json } from "stream/consumers";
 import util from "util";
 import {
   D1Database,
@@ -403,6 +404,48 @@ test("Miniflare: custom outbound service", async (t) => {
   });
 });
 
+test("Miniflare: can send GET request with body", async (t) => {
+  // https://github.com/cloudflare/workerd/issues/1122
+  const mf = new Miniflare({
+    compatibilityDate: "2023-08-01",
+    modules: true,
+    script: `export default {
+      async fetch(request) {
+        return Response.json({
+          cf: request.cf,
+          contentLength: request.headers.get("Content-Length"),
+          hasBody: request.body !== null,
+        });
+      }
+    }`,
+    cf: { key: "value" },
+  });
+  t.teardown(() => mf.dispose());
+
+  // Can't use `dispatchFetch()` here as `fetch()` prohibits `GET` requests
+  // with bodies/`Content-Length: 0` headers
+  const url = await mf.ready;
+  function get(opts: http.RequestOptions = {}): Promise<http.IncomingMessage> {
+    return new Promise((resolve, reject) => {
+      http.get(url, opts, resolve).on("error", reject);
+    });
+  }
+
+  let res = await get();
+  t.deepEqual(await json(res), {
+    cf: { key: "value" },
+    contentLength: null,
+    hasBody: false,
+  });
+
+  res = await get({ headers: { "content-length": "0" } });
+  t.deepEqual(await json(res), {
+    cf: { key: "value" },
+    contentLength: "0",
+    hasBody: true,
+  });
+});
+
 test("Miniflare: fetch mocking", async (t) => {
   const fetchMock = createFetchMock();
   fetchMock.disableNetConnect();