chore(examples): Converting Deno Streams to Web Streams (#2765)

examples/cat.ts

@@ -5,10 +5,8 @@
  * @module
  */
 
-import { copy } from "../streams/conversion.ts";
 const filenames = Deno.args;
 for (const filename of filenames) {
   const file = await Deno.open(filename);
-  await copy(file, Deno.stdout);
-  file.close();
+  await file.readable.pipeTo(Deno.stdout.writable, { preventClose: true });
 }

examples/curl.ts

@@ -8,9 +8,4 @@
 const url_ = Deno.args[0];
 const res = await fetch(url_);
 
-// TODO(ry) Re-enable streaming in this example.
-// Originally we did: await Deno.copy(res.body, Deno.stdout);
-// But maybe more JS-y would be: res.pipeTo(Deno.stdout);
-
-const body = new Uint8Array(await res.arrayBuffer());
-await Deno.stdout.write(body);
+await res.body?.pipeTo(Deno.stdout.writable);

examples/xeval.ts

@@ -6,7 +6,7 @@
  */
 
 import { parse } from "../flags/mod.ts";
-import { readStringDelim } from "../io/buffer.ts";
+import { TextDelimiterStream } from "../streams/delimiter.ts";
 
 // See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncFunction.
 const AsyncFunction = Object.getPrototypeOf(async function () {})
@@ -33,7 +33,7 @@ OPTIONS:
 ARGS:
   <code>`;
 
-export type XevalFunc = (v: string) => void;
+export type XevalFunc = (v: string) => Promise<unknown>;
 
 export interface XevalOptions {
   delimiter?: string;
@@ -42,11 +42,14 @@ export interface XevalOptions {
 const DEFAULT_DELIMITER = "\n";
 
 export async function xeval(
-  reader: Deno.Reader,
+  readable: ReadableStream<Uint8Array>,
   xevalFunc: XevalFunc,
   { delimiter = DEFAULT_DELIMITER }: XevalOptions = {},
 ) {
-  for await (const chunk of readStringDelim(reader, delimiter)) {
+  const chunks = readable
+    .pipeThrough(new TextDecoderStream())
+    .pipeThrough(new TextDelimiterStream(delimiter));
+  for await (const chunk of chunks) {
     // Ignore empty chunks.
     if (chunk.length > 0) {
       await xevalFunc(chunk);
@@ -89,7 +92,7 @@ async function main() {
 
   const xEvalFunc = new AsyncFunction(replVar, code);
 
-  await xeval(Deno.stdin, xEvalFunc, { delimiter });
+  await xeval(Deno.stdin.readable, xEvalFunc, { delimiter });
 }
 
 if (import.meta.main) {

examples/xeval_test.ts

@@ -1,22 +1,33 @@
 // Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
 import { xeval } from "./xeval.ts";
-import { StringReader } from "../io/readers.ts";
 import { assertEquals, assertStringIncludes } from "../testing/asserts.ts";
 import { dirname, fromFileUrl } from "../path/mod.ts";
 
 const moduleDir = dirname(fromFileUrl(import.meta.url));
 
+function createReadableStream(str: string) {
+  return new ReadableStream<Uint8Array>({
+    start(controller) {
+      controller.enqueue(new TextEncoder().encode(str));
+      controller.close();
+    },
+  });
+}
+
 Deno.test("xevalSuccess", async function () {
   const chunks: string[] = [];
-  await xeval(new StringReader("a\nb\nc"), ($): number => chunks.push($));
+  await xeval(
+    createReadableStream("a\nb\nc"),
+    ($) => Promise.resolve(chunks.push($)),
+  );
   assertEquals(chunks, ["a", "b", "c"]);
 });
 
 Deno.test("xevalDelimiter", async function () {
   const chunks: string[] = [];
   await xeval(
-    new StringReader("!MADMADAMADAM!"),
-    ($): number => chunks.push($),
+    createReadableStream("!MADMADAMADAM!"),
+    ($) => Promise.resolve(chunks.push($)),
     {
       delimiter: "MADAM",
     },