Flesh out open() modes (#1282)

2 files changed, 110 insertions, 4 deletions

diff --git a/js/files.ts b/js/files.ts
index ef0037511..4392eadf7 100644
--- a/js/files.ts
+++ b/js/files.ts
@@ -29,14 +29,37 @@ export const stdout = new File(1);
 /** An instance of `File` for stderr. */
 export const stderr = new File(2);
 
-// TODO This is just a placeholder - not final API.
-export type OpenMode = "r" | "w" | "w+" | "x";
+type OpenMode =
+  /** Read-only. Default. Starts at beginning of file. */
+  | "r"
+  /** Read-write. Start at beginning of file. */
+  | "r+"
+  /** Write-only. Opens and truncates existing file or creates new one for
+   * writing only.
+   */
+  | "w"
+  /** Read-write. Opens and truncates existing file or creates new one for
+   * writing and reading.
+   */
+  | "w+"
+  /** Write-only. Opens existing file or creates new one. Each write appends
+   * content to the end of file.
+   */
+  | "a"
+  /** Read-write. Behaves like "a" and allows to read from file. */
+  | "a+"
+  /** Write-only. Exclusive create - creates new file only if one doesn't exist
+   * already.
+   */
+  | "x"
+  /** Read-write. Behaves like `x` and allows to read from file. */
+  | "x+";
 
 /** A factory function for creating instances of `File` associated with the
  * supplied file name.
  */
 export function create(filename: string): Promise<File> {
-  return open(filename, "x");
+  return open(filename, "w+");
 }
 
 /** Open a file and return an instance of the `File` object.
@@ -52,8 +75,10 @@ export async function open(
 ): Promise<File> {
   const builder = flatbuffers.createBuilder();
   const filename_ = builder.createString(filename);
+  const mode_ = builder.createString(mode);
   msg.Open.startOpen(builder);
   msg.Open.addFilename(builder, filename_);
+  msg.Open.addMode(builder, mode_);
   const inner = msg.Open.endOpen(builder);
   const baseRes = await dispatch.sendAsync(builder, msg.Any.Open, inner);
   assert(baseRes != null);
diff --git a/js/files_test.ts b/js/files_test.ts
index 37f63d9fa..d46a46906 100644
--- a/js/files_test.ts
+++ b/js/files_test.ts
@@ -1,6 +1,6 @@
 // Copyright 2018 the Deno authors. All rights reserved. MIT license.
 import * as deno from "deno";
-import { test, assert, assertEqual } from "./test_util.ts";
+import { test, testPerm, assert, assertEqual } from "./test_util.ts";
 
 test(function filesStdioFileDescriptors() {
   assertEqual(deno.stdin.rid, 0);
@@ -29,3 +29,84 @@ test(async function filesToAsyncIterator() {
 
   assertEqual(totalSize, 12);
 });
+
+testPerm({ write: true }, async function createFile() {
+  const tempDir = await deno.makeTempDir();
+  const filename = tempDir + "/test.txt";
+  let f = await deno.open(filename, "w");
+  let fileInfo = deno.statSync(filename);
+  assert(fileInfo.isFile());
+  assert(fileInfo.len === 0);
+  const enc = new TextEncoder();
+  const data = enc.encode("Hello");
+  await f.write(data);
+  fileInfo = deno.statSync(filename);
+  assert(fileInfo.len === 5);
+  f.close();
+
+  // TODO: test different modes
+  await deno.removeAll(tempDir);
+});
+
+testPerm({ write: true }, async function openModeWrite() {
+  const tempDir = deno.makeTempDirSync();
+  const encoder = new TextEncoder();
+  const filename = tempDir + "hello.txt";
+  const data = encoder.encode("Hello world!\n");
+
+  let file = await deno.open(filename, "w");
+  // assert file was created
+  let fileInfo = deno.statSync(filename);
+  assert(fileInfo.isFile());
+  assertEqual(fileInfo.len, 0);
+  // write some data
+  await file.write(data);
+  fileInfo = deno.statSync(filename);
+  assertEqual(fileInfo.len, 13);
+  // assert we can't read from file
+  let thrown = false;
+  try {
+    const buf = new Uint8Array(20);
+    await file.read(buf);
+  } catch (e) {
+    thrown = true;
+  } finally {
+    assert(thrown, "'w' mode shouldn't allow to read file");
+  }
+  file.close();
+  // assert that existing file is truncated on open
+  file = await deno.open(filename, "w");
+  file.close();
+  const fileSize = deno.statSync(filename).len;
+  assertEqual(fileSize, 0);
+  await deno.removeAll(tempDir);
+});
+
+testPerm({ write: true }, async function openModeWriteRead() {
+  const tempDir = deno.makeTempDirSync();
+  const encoder = new TextEncoder();
+  const filename = tempDir + "hello.txt";
+  const data = encoder.encode("Hello world!\n");
+
+  let file = await deno.open(filename, "w+");
+  // assert file was created
+  let fileInfo = deno.statSync(filename);
+  assert(fileInfo.isFile());
+  assertEqual(fileInfo.len, 0);
+  // write some data
+  await file.write(data);
+  fileInfo = deno.statSync(filename);
+  assertEqual(fileInfo.len, 13);
+
+  // TODO: this test is not working, I expect because
+  //  file handle points to the end of file, but ATM
+  //  deno has no seek implementation on Rust side
+  // assert file can be read
+  // const buf = new Uint8Array(20);
+  // const result = await file.read(buf);
+  // console.log(result.eof, result.nread);
+  // assertEqual(result.nread, 13);
+  // file.close();
+
+  await deno.removeAll(tempDir);
+});