io: refactor BufReader/Writer interfaces to be more idiomatic (denoland/deno_std#444)

Thanks Vincent Le Goff (@zekth) for porting over the CSV reader
implementation.

Fixes: denoland/deno_std#436

Original: https://github.com/denoland/deno_std/commit/0ee6334b698072b50c6f5ac8d42d34dc4c94b948

2 files changed, 59 insertions, 58 deletions

diff --git a/textproto/mod.ts b/textproto/mod.ts
index 72ecd252f..66f303905 100644
--- a/textproto/mod.ts
+++ b/textproto/mod.ts
@@ -3,7 +3,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-import { BufReader, BufState } from "../io/bufio.ts";
+import { BufReader, EOF, UnexpectedEOFError } from "../io/bufio.ts";
 import { charCode } from "../io/util.ts";
 
 const asciiDecoder = new TextDecoder();
@@ -39,9 +39,10 @@ export class TextProtoReader {
   /** readLine() reads a single line from the TextProtoReader,
    * eliding the final \n or \r\n from the returned string.
    */
-  async readLine(): Promise<[string, BufState]> {
-    let [line, err] = await this.readLineSlice();
-    return [str(line), err];
+  async readLine(): Promise<string | EOF> {
+    const s = await this.readLineSlice();
+    if (s === EOF) return EOF;
+    return str(s);
   }
 
   /** ReadMIMEHeader reads a MIME-style header from r.
@@ -64,29 +65,31 @@ export class TextProtoReader {
    *		"Long-Key": {"Even Longer Value"},
    *	}
    */
-  async readMIMEHeader(): Promise<[Headers, BufState]> {
+  async readMIMEHeader(): Promise<Headers | EOF> {
     let m = new Headers();
     let line: Uint8Array;
 
     // The first line cannot start with a leading space.
-    let [buf, err] = await this.r.peek(1);
-    if (buf[0] == charCode(" ") || buf[0] == charCode("\t")) {
-      [line, err] = await this.readLineSlice();
+    let buf = await this.r.peek(1);
+    if (buf === EOF) {
+      return EOF;
+    } else if (buf[0] == charCode(" ") || buf[0] == charCode("\t")) {
+      line = (await this.readLineSlice()) as Uint8Array;
     }
 
-    [buf, err] = await this.r.peek(1);
-    if (err == null && (buf[0] == charCode(" ") || buf[0] == charCode("\t"))) {
+    buf = await this.r.peek(1);
+    if (buf === EOF) {
+      throw new UnexpectedEOFError();
+    } else if (buf[0] == charCode(" ") || buf[0] == charCode("\t")) {
       throw new ProtocolError(
         `malformed MIME header initial line: ${str(line)}`
       );
     }
 
     while (true) {
-      let [kv, err] = await this.readLineSlice(); // readContinuedLineSlice
-
-      if (kv.byteLength === 0) {
-        return [m, err];
-      }
+      let kv = await this.readLineSlice(); // readContinuedLineSlice
+      if (kv === EOF) throw new UnexpectedEOFError();
+      if (kv.byteLength === 0) return m;
 
       // Key ends at first colon; should not have trailing spaces
       // but they appear in the wild, violating specs, so we remove
@@ -125,29 +128,26 @@ export class TextProtoReader {
       try {
         m.append(key, value);
       } catch {}
-
-      if (err != null) {
-        throw err;
-      }
     }
   }
 
-  async readLineSlice(): Promise<[Uint8Array, BufState]> {
+  async readLineSlice(): Promise<Uint8Array | EOF> {
     // this.closeDot();
     let line: Uint8Array;
     while (true) {
-      let [l, more, err] = await this.r.readLine();
-      if (err != null) {
-        // Go's len(typed nil) works fine, but not in JS
-        return [new Uint8Array(0), err];
-      }
+      const r = await this.r.readLine();
+      if (r === EOF) return EOF;
+      const { line: l, more } = r;
 
       // Avoid the copy if the first call produced a full line.
-      if (line == null && !more) {
+      if (!line && !more) {
+        // TODO(ry):
+        // This skipSpace() is definitely misplaced, but I don't know where it
+        // comes from nor how to fix it.
         if (this.skipSpace(l) === 0) {
-          return [new Uint8Array(0), null];
+          return new Uint8Array(0);
         }
-        return [l, null];
+        return l;
       }
 
       line = append(line, l);
@@ -155,7 +155,7 @@ export class TextProtoReader {
         break;
       }
     }
-    return [line, null];
+    return line;
   }
 
   skipSpace(l: Uint8Array): number {
diff --git a/textproto/reader_test.ts b/textproto/reader_test.ts
index 2d054caba..bd0d39fd3 100644
--- a/textproto/reader_test.ts
+++ b/textproto/reader_test.ts
@@ -3,11 +3,21 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-import { BufReader } from "../io/bufio.ts";
+import { BufReader, EOF } from "../io/bufio.ts";
 import { TextProtoReader, ProtocolError } from "./mod.ts";
 import { stringsReader } from "../io/util.ts";
-import { assert, assertEquals, assertThrows } from "../testing/asserts.ts";
-import { test } from "../testing/mod.ts";
+import {
+  assert,
+  assertEquals,
+  assertNotEquals,
+  assertThrows
+} from "../testing/asserts.ts";
+import { test, runIfMain } from "../testing/mod.ts";
+
+function assertNotEOF<T extends {}>(val: T | EOF): T {
+  assertNotEquals(val, EOF);
+  return val as T;
+}
 
 function reader(s: string): TextProtoReader {
   return new TextProtoReader(new BufReader(stringsReader(s)));
@@ -21,25 +31,21 @@ function reader(s: string): TextProtoReader {
 // });
 
 test(async function textprotoReadEmpty(): Promise<void> {
-  let r = reader("");
-  let [, err] = await r.readMIMEHeader();
-  // Should not crash!
-  assertEquals(err, "EOF");
+  const r = reader("");
+  const m = await r.readMIMEHeader();
+  assertEquals(m, EOF);
 });
 
 test(async function textprotoReader(): Promise<void> {
-  let r = reader("line1\nline2\n");
-  let [s, err] = await r.readLine();
+  const r = reader("line1\nline2\n");
+  let s = await r.readLine();
   assertEquals(s, "line1");
-  assert(err == null);
 
-  [s, err] = await r.readLine();
+  s = await r.readLine();
   assertEquals(s, "line2");
-  assert(err == null);
 
-  [s, err] = await r.readLine();
-  assertEquals(s, "");
-  assert(err == "EOF");
+  s = await r.readLine();
+  assert(s === EOF);
 });
 
 test({
@@ -48,10 +54,9 @@ test({
     const input =
       "my-key: Value 1  \r\nLong-key: Even Longer Value\r\nmy-Key: Value 2\r\n\n";
     const r = reader(input);
-    const [m, err] = await r.readMIMEHeader();
+    const m = assertNotEOF(await r.readMIMEHeader());
     assertEquals(m.get("My-Key"), "Value 1, Value 2");
     assertEquals(m.get("Long-key"), "Even Longer Value");
-    assert(!err);
   }
 });
 
@@ -60,9 +65,8 @@ test({
   async fn(): Promise<void> {
     const input = "Foo: bar\n\n";
     const r = reader(input);
-    let [m, err] = await r.readMIMEHeader();
+    const m = assertNotEOF(await r.readMIMEHeader());
     assertEquals(m.get("Foo"), "bar");
-    assert(!err);
   }
 });
 
@@ -71,9 +75,8 @@ test({
   async fn(): Promise<void> {
     const input = ": bar\ntest-1: 1\n\n";
     const r = reader(input);
-    let [m, err] = await r.readMIMEHeader();
+    const m = assertNotEOF(await r.readMIMEHeader());
     assertEquals(m.get("Test-1"), "1");
-    assert(!err);
   }
 });
 
@@ -86,11 +89,9 @@ test({
       data.push("x");
     }
     const sdata = data.join("");
-    const r = reader(`Cookie: ${sdata}\r\n`);
-    let [m] = await r.readMIMEHeader();
+    const r = reader(`Cookie: ${sdata}\r\n\r\n`);
+    const m = assertNotEOF(await r.readMIMEHeader());
     assertEquals(m.get("Cookie"), sdata);
-    // TODO re-enable, here err === "EOF" is has to be null
-    // assert(!err);
   }
 });
 
@@ -106,12 +107,11 @@ test({
       "Audio Mode : None\r\n" +
       "Privilege : 127\r\n\r\n";
     const r = reader(input);
-    let [m, err] = await r.readMIMEHeader();
+    const m = assertNotEOF(await r.readMIMEHeader());
     assertEquals(m.get("Foo"), "bar");
     assertEquals(m.get("Content-Language"), "en");
     assertEquals(m.get("SID"), "0");
     assertEquals(m.get("Privilege"), "127");
-    assert(!err);
     // Not a legal http header
     assertThrows(
       (): void => {
@@ -176,9 +176,10 @@ test({
       "------WebKitFormBoundaryimeZ2Le9LjohiUiG--\r\n\n"
     ];
     const r = reader(input.join(""));
-    let [m, err] = await r.readMIMEHeader();
+    const m = assertNotEOF(await r.readMIMEHeader());
     assertEquals(m.get("Accept"), "*/*");
     assertEquals(m.get("Content-Disposition"), 'form-data; name="test"');
-    assert(!err);
   }
 });
+
+runIfMain(import.meta);