feat: fetch() now handles redirects (#2561)

js/fetch.ts

@@ -247,7 +247,7 @@ export class Response implements domTypes.Response {
   readonly url: string = "";
   statusText = "FIXME"; // TODO
   readonly type = "basic"; // TODO
-  redirected = false; // TODO
+  readonly redirected: boolean;
   headers: domTypes.Headers;
   readonly trailer: Promise<domTypes.Headers>;
   bodyUsed = false;
@@ -257,6 +257,7 @@ export class Response implements domTypes.Response {
     readonly status: number,
     headersList: Array<[string, string]>,
     rid: number,
+    redirected_: boolean,
     body_: null | Body = null
   ) {
     this.trailer = createResolvable();
@@ -268,6 +269,8 @@ export class Response implements domTypes.Response {
     } else {
       this.body = body_;
     }
+
+    this.redirected = redirected_;
   }
 
   async arrayBuffer(): Promise<ArrayBuffer> {
@@ -308,7 +311,13 @@ export class Response implements domTypes.Response {
       headersList.push(header);
     }
 
-    return new Response(this.status, headersList, -1, this.body);
+    return new Response(
+      this.status,
+      headersList,
+      -1,
+      this.redirected,
+      this.body
+    );
   }
 }
 
@@ -352,6 +361,29 @@ function deserializeHeaderFields(m: msg.HttpHeader): Array<[string, string]> {
   return out;
 }
 
+async function getFetchRes(
+  url: string,
+  method: string | null,
+  headers: domTypes.Headers | null,
+  body: ArrayBufferView | undefined
+): Promise<msg.FetchRes> {
+  // Send Fetch message
+  const builder = flatbuffers.createBuilder();
+  const headerOff = msgHttpRequest(builder, url, method, headers);
+  const resBase = await sendAsync(
+    builder,
+    msg.Any.Fetch,
+    msg.Fetch.createFetch(builder, headerOff),
+    body
+  );
+
+  // Decode FetchRes
+  assert(msg.Any.FetchRes === resBase.innerType());
+  const inner = new msg.FetchRes();
+  assert(resBase.inner(inner) != null);
+  return inner;
+}
+
 /** Fetch a resource from the network. */
 export async function fetch(
   input: domTypes.Request | string,
@@ -361,6 +393,8 @@ export async function fetch(
   let method: string | null = null;
   let headers: domTypes.Headers | null = null;
   let body: ArrayBufferView | undefined;
+  let redirected = false;
+  let remRedirectCount = 20; // TODO: use a better way to handle
 
   if (typeof input === "string") {
     url = input;
@@ -414,28 +448,48 @@ export async function fetch(
     }
   }
 
-  // Send Fetch message
-  const builder = flatbuffers.createBuilder();
-  const headerOff = msgHttpRequest(builder, url, method, headers);
-  const resBase = await sendAsync(
-    builder,
-    msg.Any.Fetch,
-    msg.Fetch.createFetch(builder, headerOff),
-    body
-  );
+  while (remRedirectCount) {
+    const inner = await getFetchRes(url, method, headers, body);
 
-  // Decode FetchRes
-  assert(msg.Any.FetchRes === resBase.innerType());
-  const inner = new msg.FetchRes();
-  assert(resBase.inner(inner) != null);
+    const header = inner.header()!;
+    const bodyRid = inner.bodyRid();
+    assert(!header.isRequest());
+    const status = header.status();
 
-  const header = inner.header()!;
-  const bodyRid = inner.bodyRid();
-  assert(!header.isRequest());
-  const status = header.status();
+    const headersList = deserializeHeaderFields(header);
 
-  const headersList = deserializeHeaderFields(header);
-
-  const response = new Response(status, headersList, bodyRid);
-  return response;
+    const response = new Response(status, headersList, bodyRid, redirected);
+    if ([301, 302, 303, 307, 308].includes(response.status)) {
+      // We're in a redirect status
+      switch ((init && init.redirect) || "follow") {
+        case "error":
+          throw notImplemented();
+        case "manual":
+          throw notImplemented();
+        case "follow":
+        default:
+          let redirectUrl = response.headers.get("Location");
+          if (redirectUrl == null) {
+            return response; // Unspecified
+          }
+          if (
+            !redirectUrl.startsWith("http://") &&
+            !redirectUrl.startsWith("https://")
+          ) {
+            redirectUrl =
+              url.split("//")[0] +
+              "//" +
+              url.split("//")[1].split("/")[0] +
+              redirectUrl; // TODO: handle relative redirection more gracefully
+          }
+          url = redirectUrl;
+          redirected = true;
+          remRedirectCount--;
+      }
+    } else {
+      return response;
+    }
+  }
+  // Return a network error due to too many redirections
+  throw notImplemented();
 }

js/fetch_test.ts

@@ -99,6 +99,32 @@ testPerm(
   }
 );
 
+testPerm({ net: true }, async function fetchWithRedirection(): Promise<void> {
+  const response = await fetch("http://localhost:4546/"); // will redirect to http://localhost:4545/
+  assertEquals(response.status, 200);
+  const body = await response.text();
+  assert(body.includes("<title>Directory listing for /</title>"));
+});
+
+testPerm({ net: true }, async function fetchWithRelativeRedirection(): Promise<
+  void
+> {
+  const response = await fetch("http://localhost:4545/tests"); // will redirect to /tests/
+  assertEquals(response.status, 200);
+  const body = await response.text();
+  assert(body.includes("<title>Directory listing for /tests/</title>"));
+});
+
+// The feature below is not implemented, but the test should work after implementation
+/*
+testPerm({ net: true }, async function fetchWithInfRedirection(): Promise<
+  void
+> {
+  const response = await fetch("http://localhost:4549/tests"); // will redirect to the same place
+  assertEquals(response.status, 0); // network error
+});
+*/
+
 testPerm({ net: true }, async function fetchInitStringBody(): Promise<void> {
   const data = "Hello World";
   const response = await fetch("http://localhost:4545/echo_server", {

tools/http_server.py

@@ -16,6 +16,7 @@ PORT = 4545
 REDIRECT_PORT = 4546
 ANOTHER_REDIRECT_PORT = 4547
 DOUBLE_REDIRECTS_PORT = 4548
+INF_REDIRECTS_PORT = 4549
 
 QUIET = '-v' not in sys.argv and '--verbose' not in sys.argv
 
@@ -153,6 +154,11 @@ def double_redirects_server():
     return base_redirect_server(DOUBLE_REDIRECTS_PORT, REDIRECT_PORT)
 
 
+# redirect server that points to itself
+def inf_redirects_server():
+    return base_redirect_server(INF_REDIRECTS_PORT, INF_REDIRECTS_PORT)
+
+
 def start(s):
     thread = Thread(target=s.serve_forever, kwargs={"poll_interval": 0.05})
     thread.daemon = True
@@ -175,7 +181,7 @@ def spawn():
 
 def main():
     servers = (server(), redirect_server(), another_redirect_server(),
-               double_redirects_server())
+               double_redirects_server(), inf_redirects_server())
     try:
         while all(s.thread.is_alive() for s in servers):
             sleep(10)