Check allow-net in fetch

js/fetch.ts

@@ -166,8 +166,7 @@ class FetchRequest {
     fbs.FetchReq.addId(builder, this.id);
     fbs.FetchReq.addUrl(builder, url);
     const msg = fbs.FetchReq.endFetchReq(builder);
-    const res = send(builder, fbs.Any.FetchReq, msg);
-    assert(res == null);
+    send(builder, fbs.Any.FetchReq, msg);
   }
 }
 
@@ -177,7 +176,7 @@ export function fetch(
 ): Promise<Response> {
   const fetchReq = new FetchRequest(input as string);
   const response = fetchReq.response;
-  return new Promise((resolve, reject) => {
+  const promise = new Promise<Response>((resolve, reject) => {
     response.onHeader = (response: FetchResponse) => {
       log("onHeader");
       resolve(response);
@@ -186,6 +185,7 @@ export function fetch(
       log("onError", error);
       reject(error);
     };
-    fetchReq.start();
   });
+  fetchReq.start();
+  return promise;
 }

js/fetch_test.ts

 // Copyright 2018 the Deno authors. All rights reserved. MIT license.
-import { testPerm, assertEqual } from "./test_util.ts";
+import { test, testPerm, assert, assertEqual } from "./test_util.ts";
 import * as deno from "deno";
 
 testPerm({ net: true }, async function fetchJsonSuccess() {
@@ -7,3 +7,15 @@ testPerm({ net: true }, async function fetchJsonSuccess() {
   const json = await response.json();
   assertEqual(json.name, "deno");
 });
+
+test(async function fetchPerm() {
+  let err;
+  try {
+    await fetch("http://localhost:4545/package.json");
+  } catch (err_) {
+    err = err_;
+  }
+  // TODO assert(err instanceof deno.PermissionDenied).
+  assert(err);
+  assertEqual(err.name, "deno.PermissionDenied");
+});

src/handlers.rs

@@ -289,10 +289,17 @@ fn handle_fetch_req(
   base: msg::Base,
   _builder: &mut FlatBufferBuilder,
 ) -> HandlerResult {
+  let deno = from_c(d);
+  if !deno.flags.allow_net {
+    let err = std::io::Error::new(
+      std::io::ErrorKind::PermissionDenied,
+      "allow_net is off.",
+    );
+    return Err(err.into());
+  }
   let msg = base.msg_as_fetch_req().unwrap();
   let id = msg.id();
   let url = msg.url().unwrap();
-  let deno = from_c(d);
   let url = url.parse::<hyper::Uri>().unwrap();
   let client = Client::new();