feat: top-level-for-await (#3212)

18 files changed, 257 insertions, 263 deletions

diff --git a/.prettierignore b/.prettierignore
index 2504e5517..589a2a3a4 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -1,5 +1,6 @@
 cli/tests/error_syntax.js
 cli/tests/badly_formatted.js
+cli/tests/top_level_for_await.js
 std/**/testdata
 std/**/vendor
-std/node_modules
\ No newline at end of file
+std/node_modules
diff --git a/cli/js/compiler.ts b/cli/js/compiler.ts
index 57e5e3a47..e4953cee2 100644
--- a/cli/js/compiler.ts
+++ b/cli/js/compiler.ts
@@ -616,6 +616,9 @@ window.compilerMain = function compilerMain(): void {
 
       diagnostics = ts.getPreEmitDiagnostics(program).filter(
         ({ code }): boolean => {
+          // TS1103: 'for-await-of' statement is only allowed within an async
+          // function or async generator.
+          if (code === 1103) return false;
           // TS1308: 'await' expression is only allowed within an async
           // function.
           if (code === 1308) return false;
diff --git a/cli/tests/045_proxy_client.ts b/cli/tests/045_proxy_client.ts
index 3d7003750..221ac57f6 100644
--- a/cli/tests/045_proxy_client.ts
+++ b/cli/tests/045_proxy_client.ts
@@ -1,7 +1,3 @@
 // Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
-async function main(): Promise<void> {
-  const res = await fetch("http://localhost:4545/std/examples/colors.ts");
-  console.log(`Response http: ${await res.text()}`);
-}
-
-main();
+const res = await fetch("http://localhost:4545/std/examples/colors.ts");
+console.log(`Response http: ${await res.text()}`);
diff --git a/cli/tests/045_proxy_test.ts b/cli/tests/045_proxy_test.ts
index 0e7225b3f..98225dbf1 100644
--- a/cli/tests/045_proxy_test.ts
+++ b/cli/tests/045_proxy_test.ts
@@ -55,11 +55,7 @@ async function testModuleDownload(): Promise<void> {
   http.close();
 }
 
-async function main(): Promise<void> {
-  proxyServer();
-  await testFetch();
-  await testModuleDownload();
-  Deno.exit(0);
-}
-
-main();
+proxyServer();
+await testFetch();
+await testModuleDownload();
+Deno.exit(0);
diff --git a/cli/tests/integration_tests.rs b/cli/tests/integration_tests.rs
index ee8f1384c..09f148736 100644
--- a/cli/tests/integration_tests.rs
+++ b/cli/tests/integration_tests.rs
@@ -597,3 +597,13 @@ itest!(top_level_await_ts {
   args: "--allow-read top_level_await.ts",
   output: "top_level_await.out",
 });
+
+itest!(top_level_for_await {
+  args: "top_level_for_await.js",
+  output: "top_level_for_await.out",
+});
+
+itest!(top_level_for_await_ts {
+  args: "top_level_for_await.ts",
+  output: "top_level_for_await.out",
+});
diff --git a/cli/tests/top_level_for_await.js b/cli/tests/top_level_for_await.js
new file mode 100644
index 000000000..fa3b496a8
--- /dev/null
+++ b/cli/tests/top_level_for_await.js
@@ -0,0 +1,10 @@
+async function* asyncGenerator() {
+  let i = 0;
+  while (i < 3) {
+    yield i++;
+  }
+}
+
+for await (const num of asyncGenerator()) {
+  console.log(num);
+};
diff --git a/cli/tests/top_level_for_await.out b/cli/tests/top_level_for_await.out
new file mode 100644
index 000000000..4539bbf2d
--- /dev/null
+++ b/cli/tests/top_level_for_await.out
@@ -0,0 +1,3 @@
+0
+1
+2
diff --git a/cli/tests/top_level_for_await.ts b/cli/tests/top_level_for_await.ts
new file mode 100644
index 000000000..9179322d7
--- /dev/null
+++ b/cli/tests/top_level_for_await.ts
@@ -0,0 +1,10 @@
+async function* asyncGenerator(): AsyncIterableIterator<number> {
+  let i = 0;
+  while (i < 3) {
+    yield i++;
+  }
+}
+
+for await (const num of asyncGenerator()) {
+  console.log(num);
+}
diff --git a/std/examples/cat.ts b/std/examples/cat.ts
index 3626e3c29..9e713d862 100644
--- a/std/examples/cat.ts
+++ b/std/examples/cat.ts
@@ -1,10 +1,7 @@
 // Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
-async function cat(filenames: string[]): Promise<void> {
-  for (const filename of filenames) {
-    const file = await Deno.open(filename);
-    await Deno.copy(Deno.stdout, file);
-    file.close();
-  }
+const filenames = Deno.args.slice(1);
+for (const filename of filenames) {
+  const file = await Deno.open(filename);
+  await Deno.copy(Deno.stdout, file);
+  file.close();
 }
-
-cat(Deno.args.slice(1));
diff --git a/std/examples/catj.ts b/std/examples/catj.ts
index cbe06d4b8..87fd6a964 100644
--- a/std/examples/catj.ts
+++ b/std/examples/catj.ts
@@ -79,32 +79,28 @@ function print(data: any): void {
   }
 }
 
-async function main(): Promise<void> {
-  const parsedArgs = parse(Deno.args.slice(1));
-
-  if (parsedArgs.h || parsedArgs.help || parsedArgs._.length === 0) {
-    console.log("Usage: catj [-h|--help] [file...]");
-    console.log();
-    console.log("Examples:");
-    console.log();
-    console.log("// print file:\n   catj file.json");
-    console.log();
-    console.log("// print multiple files:\n   catj file1.json file2.json");
-    console.log();
-    console.log("// print from stdin:\n   cat file.json | catj -");
-  }
+const parsedArgs = parse(Deno.args.slice(1));
+
+if (parsedArgs.h || parsedArgs.help || parsedArgs._.length === 0) {
+  console.log("Usage: catj [-h|--help] [file...]");
+  console.log();
+  console.log("Examples:");
+  console.log();
+  console.log("// print file:\n   catj file.json");
+  console.log();
+  console.log("// print multiple files:\n   catj file1.json file2.json");
+  console.log();
+  console.log("// print from stdin:\n   cat file.json | catj -");
+}
 
-  if (parsedArgs._[0] === "-") {
-    const contents = await Deno.readAll(Deno.stdin);
-    const json = JSON.parse(decoder.decode(contents));
+if (parsedArgs._[0] === "-") {
+  const contents = await Deno.readAll(Deno.stdin);
+  const json = JSON.parse(decoder.decode(contents));
+  print(json);
+} else {
+  for (const fileName of parsedArgs._) {
+    const fileContents = await Deno.readFile(fileName);
+    const json = JSON.parse(decoder.decode(fileContents));
     print(json);
-  } else {
-    for (const fileName of parsedArgs._) {
-      const fileContents = await Deno.readFile(fileName);
-      const json = JSON.parse(decoder.decode(fileContents));
-      print(json);
-    }
   }
 }
-
-main();
diff --git a/std/examples/curl.ts b/std/examples/curl.ts
index 04dd9d601..e020016f8 100644
--- a/std/examples/curl.ts
+++ b/std/examples/curl.ts
@@ -1,8 +1,4 @@
 // Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
-async function curl(url: string): Promise<void> {
-  const res = await fetch(url);
-  await Deno.copy(Deno.stdout, res.body);
-}
-
-await curl(Deno.args[1]);
-Deno.exit(0);
+const url = Deno.args[1];
+const res = await fetch(url);
+await Deno.copy(Deno.stdout, res.body);
diff --git a/std/http/README.md b/std/http/README.md
index e4086c1a4..26fe25bf6 100644
--- a/std/http/README.md
+++ b/std/http/README.md
@@ -56,14 +56,11 @@ console.log("Set-Cookie:", cookieHeader);
 ```typescript
 import { serve } from "https://deno.land/std/http/server.ts";
 const s = serve("0.0.0.0:8000");
+const body = new TextEncoder().encode("Hello World\n");
 
-async function main() {
-  for await (const req of s) {
-    req.respond({ body: new TextEncoder().encode("Hello World\n") });
-  }
+for await (const req of s) {
+  req.respond({ body });
 }
-
-main();
 ```
 
 ### File Server
diff --git a/std/http/testdata/simple_server.ts b/std/http/testdata/simple_server.ts
index 67b957ad5..d53e72dcf 100644
--- a/std/http/testdata/simple_server.ts
+++ b/std/http/testdata/simple_server.ts
@@ -2,10 +2,8 @@
 // This is an example of a server that responds with an empty body
 import { serve } from "../server.ts";
 
-window.onload = async function main() {
-  const addr = "0.0.0.0:4502";
-  console.log(`Simple server listening on ${addr}`);
-  for await (const req of serve(addr)) {
-    req.respond({});
-  }
+const addr = "0.0.0.0:4502";
+console.log(`Simple server listening on ${addr}`);
+for await (const req of serve(addr)) {
+  req.respond({});
 }
diff --git a/std/manual.md b/std/manual.md
index 03042c0fd..6da2d0ec2 100644
--- a/std/manual.md
+++ b/std/manual.md
@@ -937,12 +937,10 @@ Example:
 
 import { serve } from "http/server.ts";
 
-window.onload = async function() {
-  const body = new TextEncoder().encode("Hello World\n");
-  for await (const req of serve(":8000")) {
-    req.respond({ body });
-  }
-};
+const body = new TextEncoder().encode("Hello World\n");
+for await (const req of serve(":8000")) {
+  req.respond({ body });
+}
 ```
 
 ```shell
diff --git a/std/ws/README.md b/std/ws/README.md
index fe5bae983..271bf2afb 100644
--- a/std/ws/README.md
+++ b/std/ws/README.md
@@ -15,61 +15,56 @@ import {
   WebSocket
 } from "https://deno.land/std/ws/mod.ts";
 
+/** websocket echo server */
 const port = Deno.args[1] || "8080";
-async function main(): Promise<void> {
-  console.log(`websocket server is running on :${port}`);
-  for await (const req of serve(`:${port}`)) {
-    const { headers, conn } = req;
-    acceptWebSocket({
-      conn,
-      headers,
-      bufReader: req.r,
-      bufWriter: req.w
-    })
-      .then(
-        async (sock: WebSocket): Promise<void> => {
-          console.log("socket connected!");
-          const it = sock.receive();
-          while (true) {
-            try {
-              const { done, value } = await it.next();
-              if (done) {
-                break;
-              }
-              const ev = value;
-              if (typeof ev === "string") {
-                // text message
-                console.log("ws:Text", ev);
-                await sock.send(ev);
-              } else if (ev instanceof Uint8Array) {
-                // binary message
-                console.log("ws:Binary", ev);
-              } else if (isWebSocketPingEvent(ev)) {
-                const [, body] = ev;
-                // ping
-                console.log("ws:Ping", body);
-              } else if (isWebSocketCloseEvent(ev)) {
-                // close
-                const { code, reason } = ev;
-                console.log("ws:Close", code, reason);
-              }
-            } catch (e) {
-              console.error(`failed to receive frame: ${e}`);
-              await sock.close(1000).catch(console.error);
+console.log(`websocket server is running on :${port}`);
+for await (const req of serve(`:${port}`)) {
+  const { headers, conn } = req;
+  acceptWebSocket({
+    conn,
+    headers,
+    bufReader: req.r,
+    bufWriter: req.w
+  })
+    .then(
+      async (sock: WebSocket): Promise<void> => {
+        console.log("socket connected!");
+        const it = sock.receive();
+        while (true) {
+          try {
+            const { done, value } = await it.next();
+            if (done) {
+              break;
             }
+            const ev = value;
+            if (typeof ev === "string") {
+              // text message
+              console.log("ws:Text", ev);
+              await sock.send(ev);
+            } else if (ev instanceof Uint8Array) {
+              // binary message
+              console.log("ws:Binary", ev);
+            } else if (isWebSocketPingEvent(ev)) {
+              const [, body] = ev;
+              // ping
+              console.log("ws:Ping", body);
+            } else if (isWebSocketCloseEvent(ev)) {
+              // close
+              const { code, reason } = ev;
+              console.log("ws:Close", code, reason);
+            }
+          } catch (e) {
+            console.error(`failed to receive frame: ${e}`);
+            await sock.close(1000).catch(console.error);
           }
         }
-      )
-      .catch(
-        (err: Error): void => {
-          console.error(`failed to accept websocket: ${err}`);
-        }
-      );
-  }
-}
-
-if (import.meta.main) {
-  main();
+      }
+    )
+    .catch(
+      (err: Error): void => {
+        console.error(`failed to accept websocket: ${err}`);
+      }
+    );
 }
 ```
 
@@ -88,46 +83,49 @@ import { TextProtoReader } from "https://deno.land/std/textproto/mod.ts";
 import { blue, green, red, yellow } from "https://deno.land/std/fmt/colors.ts";
 
 const endpoint = Deno.args[1] || "ws://127.0.0.1:8080";
-async function main(): Promise<void> {
-  const sock = await connectWebSocket(endpoint);
-  console.log(green("ws connected! (type 'close' to quit)"));
-  (async function(): Promise<void> {
-    for await (const msg of sock.receive()) {
-      if (typeof msg === "string") {
-        console.log(yellow("< " + msg));
-      } else if (isWebSocketPingEvent(msg)) {
-        console.log(blue("< ping"));
-      } else if (isWebSocketPongEvent(msg)) {
-        console.log(blue("< pong"));
-      } else if (isWebSocketCloseEvent(msg)) {
-        console.log(red(`closed: code=${msg.code}, reason=${msg.reason}`));
-      }
+/** simple websocket cli */
+const sock = await connectWebSocket(endpoint);
+console.log(green("ws connected! (type 'close' to quit)"));
+(async function(): Promise<void> {
+  for await (const msg of sock.receive()) {
+    if (typeof msg === "string") {
+      console.log(yellow("< " + msg));
+    } else if (isWebSocketPingEvent(msg)) {
+      console.log(blue("< ping"));
+    } else if (isWebSocketPongEvent(msg)) {
+      console.log(blue("< pong"));
+    } else if (isWebSocketCloseEvent(msg)) {
+      console.log(red(`closed: code=${msg.code}, reason=${msg.reason}`));
     }
-  })();
-  const tpr = new TextProtoReader(new BufReader(Deno.stdin));
-  while (true) {
-    await Deno.stdout.write(encode("> "));
-    const [line, err] = await tpr.readLine();
-    if (err) {
-      console.error(red(`failed to read line from stdin: ${err}`));
-      break;
-    }
-    if (line === "close") {
-      break;
-    } else if (line === "ping") {
-      await sock.ping();
-    } else {
-      await sock.send(line);
-    }
-    await new Promise((resolve): number => setTimeout(resolve, 0));
   }
-  await sock.close(1000);
-  Deno.exit(0);
-}
-
-if (import.meta.main) {
-  main();
+})();
+
+const tpr = new TextProtoReader(new BufReader(Deno.stdin));
+while (true) {
+  await Deno.stdout.write(encode("> "));
+  const [line, err] = await tpr.readLine();
+  if (err) {
+    console.error(red(`failed to read line from stdin: ${err}`));
+    break;
+  }
+  if (line === "close") {
+    break;
+  } else if (line === "ping") {
+    await sock.ping();
+  } else {
+    await sock.send(line);
+  }
+  // FIXME: Without this,
+  // sock.receive() won't resolved though it is readable...
+  await new Promise(
+    (resolve): void => {
+      setTimeout(resolve, 0);
+    }
+  );
 }
+await sock.close(1000);
+// FIXME: conn.close() won't shutdown process...
+Deno.exit(0);
 ```
 
 ## API
diff --git a/std/ws/example_client.ts b/std/ws/example_client.ts
index a6649570e..3b132281f 100644
--- a/std/ws/example_client.ts
+++ b/std/ws/example_client.ts
@@ -11,50 +11,45 @@ import { blue, green, red, yellow } from "../fmt/colors.ts";
 
 const endpoint = Deno.args[1] || "ws://127.0.0.1:8080";
 /** simple websocket cli */
-async function main(): Promise<void> {
-  const sock = await connectWebSocket(endpoint);
-  console.log(green("ws connected! (type 'close' to quit)"));
-  (async function(): Promise<void> {
-    for await (const msg of sock.receive()) {
-      if (typeof msg === "string") {
-        console.log(yellow("< " + msg));
-      } else if (isWebSocketPingEvent(msg)) {
-        console.log(blue("< ping"));
-      } else if (isWebSocketPongEvent(msg)) {
-        console.log(blue("< pong"));
-      } else if (isWebSocketCloseEvent(msg)) {
-        console.log(red(`closed: code=${msg.code}, reason=${msg.reason}`));
-      }
+const sock = await connectWebSocket(endpoint);
+console.log(green("ws connected! (type 'close' to quit)"));
+(async function(): Promise<void> {
+  for await (const msg of sock.receive()) {
+    if (typeof msg === "string") {
+      console.log(yellow("< " + msg));
+    } else if (isWebSocketPingEvent(msg)) {
+      console.log(blue("< ping"));
+    } else if (isWebSocketPongEvent(msg)) {
+      console.log(blue("< pong"));
+    } else if (isWebSocketCloseEvent(msg)) {
+      console.log(red(`closed: code=${msg.code}, reason=${msg.reason}`));
     }
-  })();
-  const tpr = new TextProtoReader(new BufReader(Deno.stdin));
-  while (true) {
-    await Deno.stdout.write(encode("> "));
-    const [line, err] = await tpr.readLine();
-    if (err) {
-      console.error(red(`failed to read line from stdin: ${err}`));
-      break;
-    }
-    if (line === "close") {
-      break;
-    } else if (line === "ping") {
-      await sock.ping();
-    } else {
-      await sock.send(line);
-    }
-    // FIXME: Without this,
-    // sock.receive() won't resolved though it is readable...
-    await new Promise(
-      (resolve): void => {
-        setTimeout(resolve, 0);
-      }
-    );
   }
-  await sock.close(1000);
-  // FIXME: conn.close() won't shutdown process...
-  Deno.exit(0);
-}
+})();
 
-if (import.meta.main) {
-  main();
+const tpr = new TextProtoReader(new BufReader(Deno.stdin));
+while (true) {
+  await Deno.stdout.write(encode("> "));
+  const [line, err] = await tpr.readLine();
+  if (err) {
+    console.error(red(`failed to read line from stdin: ${err}`));
+    break;
+  }
+  if (line === "close") {
+    break;
+  } else if (line === "ping") {
+    await sock.ping();
+  } else {
+    await sock.send(line);
+  }
+  // FIXME: Without this,
+  // sock.receive() won't resolved though it is readable...
+  await new Promise(
+    (resolve): void => {
+      setTimeout(resolve, 0);
+    }
+  );
 }
+await sock.close(1000);
+// FIXME: conn.close() won't shutdown process...
+Deno.exit(0);
diff --git a/std/ws/example_server.ts b/std/ws/example_server.ts
index cd51ff94c..ea981256e 100644
--- a/std/ws/example_server.ts
+++ b/std/ws/example_server.ts
@@ -9,58 +9,52 @@ import {
 
 /** websocket echo server */
 const port = Deno.args[1] || "8080";
-async function main(): Promise<void> {
-  console.log(`websocket server is running on :${port}`);
-  for await (const req of serve(`:${port}`)) {
-    const { headers, conn } = req;
-    acceptWebSocket({
-      conn,
-      headers,
-      bufReader: req.r,
-      bufWriter: req.w
-    })
-      .then(
-        async (sock: WebSocket): Promise<void> => {
-          console.log("socket connected!");
-          const it = sock.receive();
-          while (true) {
-            try {
-              const { done, value } = await it.next();
-              if (done) {
-                break;
-              }
-              const ev = value;
-              if (typeof ev === "string") {
-                // text message
-                console.log("ws:Text", ev);
-                await sock.send(ev);
-              } else if (ev instanceof Uint8Array) {
-                // binary message
-                console.log("ws:Binary", ev);
-              } else if (isWebSocketPingEvent(ev)) {
-                const [, body] = ev;
-                // ping
-                console.log("ws:Ping", body);
-              } else if (isWebSocketCloseEvent(ev)) {
-                // close
-                const { code, reason } = ev;
-                console.log("ws:Close", code, reason);
-              }
-            } catch (e) {
-              console.error(`failed to receive frame: ${e}`);
-              await sock.close(1000).catch(console.error);
+console.log(`websocket server is running on :${port}`);
+for await (const req of serve(`:${port}`)) {
+  const { headers, conn } = req;
+  acceptWebSocket({
+    conn,
+    headers,
+    bufReader: req.r,
+    bufWriter: req.w
+  })
+    .then(
+      async (sock: WebSocket): Promise<void> => {
+        console.log("socket connected!");
+        const it = sock.receive();
+        while (true) {
+          try {
+            const { done, value } = await it.next();
+            if (done) {
+              break;
             }
+            const ev = value;
+            if (typeof ev === "string") {
+              // text message
+              console.log("ws:Text", ev);
+              await sock.send(ev);
+            } else if (ev instanceof Uint8Array) {
+              // binary message
+              console.log("ws:Binary", ev);
+            } else if (isWebSocketPingEvent(ev)) {
+              const [, body] = ev;
+              // ping
+              console.log("ws:Ping", body);
+            } else if (isWebSocketCloseEvent(ev)) {
+              // close
+              const { code, reason } = ev;
+              console.log("ws:Close", code, reason);
+            }
+          } catch (e) {
+            console.error(`failed to receive frame: ${e}`);
+            await sock.close(1000).catch(console.error);
           }
         }
-      )
-      .catch(
-        (err: Error): void => {
-          console.error(`failed to accept websocket: ${err}`);
-        }
-      );
-  }
-}
-
-if (import.meta.main) {
-  main();
+      }
+    )
+    .catch(
+      (err: Error): void => {
+        console.error(`failed to accept websocket: ${err}`);
+      }
+    );
 }
diff --git a/tools/deno_http_proxy.ts b/tools/deno_http_proxy.ts
index 728e4fd3f..5f601723a 100644
--- a/tools/deno_http_proxy.ts
+++ b/tools/deno_http_proxy.ts
@@ -5,13 +5,6 @@ const addr = Deno.args[1] || "127.0.0.1:4500";
 const originAddr = Deno.args[2] || "127.0.0.1:4501";
 const server = serve(addr);
 
-async function main(): Promise<void> {
-  console.log(`Proxy listening on http://${addr}/`);
-  for await (const req of server) {
-    proxyRequest(req);
-  }
-}
-
 async function proxyRequest(req: ServerRequest): Promise<void> {
   const url = `http://${originAddr}${req.url}`;
   const resp = await fetch(url, {
@@ -21,4 +14,7 @@ async function proxyRequest(req: ServerRequest): Promise<void> {
   req.respond(resp);
 }
 
-main();
+console.log(`Proxy listening on http://${addr}/`);
+for await (const req of server) {
+  proxyRequest(req);
+}