fix(io/bufio): fix handling of trailing new line (#990)

io/bufio.ts

@@ -7,7 +7,7 @@
 type Reader = Deno.Reader;
 type Writer = Deno.Writer;
 type WriterSync = Deno.WriterSync;
-import { copy } from "../bytes/mod.ts";
+import { concat, copy } from "../bytes/mod.ts";
 import { assert } from "../_util/assert.ts";
 import { BytesList } from "../bytes/bytes_list.ts";
 import { writeAll, writeAllSync } from "./util.ts";
@@ -252,6 +252,9 @@ export class BufReader implements Reader {
     try {
       line = await this.readSlice(LF);
     } catch (err) {
+      if (err instanceof Deno.errors.BadResource) {
+        throw err;
+      }
       let { partial } = err;
       assert(
         partial instanceof Uint8Array,
@@ -707,13 +710,21 @@ export async function* readLines(
     ignoreBOM?: boolean;
   },
 ): AsyncIterableIterator<string> {
-  for await (let chunk of readStringDelim(reader, "\n", decoderOpts)) {
-    // Finding a CR at the end of the line is evidence of a
-    // "\r\n" at the end of the line. The "\r" part should be
-    // removed too.
-    if (chunk.endsWith("\r")) {
-      chunk = chunk.slice(0, -1);
+  const bufReader = new BufReader(reader);
+  let chunks: Uint8Array[] = [];
+  const decoder = new TextDecoder(decoderOpts?.encoding, decoderOpts);
+  while (true) {
+    const res = await bufReader.readLine();
+    if (!res) {
+      if (chunks.length > 0) {
+        yield decoder.decode(concat(...chunks));
+      }
+      break;
+    }
+    chunks.push(res.line);
+    if (!res.more) {
+      yield decoder.decode(concat(...chunks));
+      chunks = [];
     }
-    yield chunk;
   }
 }

io/bufio_test.ts

@@ -3,7 +3,12 @@
 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
-import { assert, assertEquals, fail } from "../testing/asserts.ts";
+import {
+  assert,
+  assertEquals,
+  assertThrowsAsync,
+  fail,
+} from "../testing/asserts.ts";
 import {
   BufferFullError,
   BufReader,
@@ -242,6 +247,15 @@ Deno.test("bufioReadLine", async function () {
   await testReadLine(testInputrn);
 });
 
+Deno.test("bufioReadLineBadResource", async () => {
+  const file = await Deno.open("README.md");
+  const bufReader = new BufReader(file);
+  file.close();
+  assertThrowsAsync(async () => {
+    await bufReader.readLine();
+  }, Deno.errors.BadResource);
+});
+
 Deno.test("[io] readStringDelim basic", async () => {
   const delim = "!#$%&()=~";
   const exp = [
@@ -480,6 +494,7 @@ Deno.test("readStringDelimAndLines", async function () {
   assertEquals(chunks_, ["Hello World", "Hello World 2", "Hello World 3"]);
 
   const linesData = new Buffer(enc.encode("0\n1\n2\n3\n4\n5\n6\n7\n8\n9"));
+  const linesDataWithTrailingNewLine = new Buffer(enc.encode("1\n2\n3\n"));
   // consider data with windows newlines too
   const linesDataWindows = new Buffer(
     enc.encode("0\r\n1\r\n2\r\n3\r\n4\r\n5\r\n6\r\n7\r\n8\r\n9"),
@@ -493,6 +508,14 @@ Deno.test("readStringDelimAndLines", async function () {
   assertEquals(lines_.length, 10);
   assertEquals(lines_, ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]);
 
+  lines_.length = 0;
+  for await (const l of readLines(linesDataWithTrailingNewLine)) {
+    lines_.push(l);
+  }
+
+  assertEquals(lines_.length, 3);
+  assertEquals(lines_, ["1", "2", "3"]); // No empty line at the end
+
   // Now test for "windows" lines
   lines_.length = 0;
   for await (const l of readLines(linesDataWindows)) {
@@ -512,7 +535,7 @@ Deno.test("readLinesWithEncodingISO-8859-15", async function () {
 
   Deno.close(file_.rid);
 
-  assertEquals(lines_.length, 13);
+  assertEquals(lines_.length, 12);
   assertEquals(lines_, [
     "\u0020!\"#$%&'()*+,-./",
     "0123456789:;<=>?",
@@ -526,7 +549,6 @@ Deno.test("readLinesWithEncodingISO-8859-15", async function () {
     "ÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞß",
     "àáâãäåæçèéêëìíîï",
     "ðñòóôõö÷øùúûüýþÿ",
-    "",
   ]);
 });