Implement deno.readlink() (#797)

4 files changed, 93 insertions, 1 deletions

diff --git a/js/deno.ts b/js/deno.ts
index dd6539163..3bbda69e8 100644
--- a/js/deno.ts
+++ b/js/deno.ts
@@ -5,8 +5,9 @@ export { env, exit } from "./os";
 export { mkdirSync, mkdir } from "./mkdir";
 export { makeTempDirSync, makeTempDir } from "./make_temp_dir";
 export { removeSync, remove, removeAllSync, removeAll } from "./remove";
-export { readFileSync, readFile } from "./read_file";
 export { renameSync, rename } from "./rename";
+export { readFileSync, readFile } from "./read_file";
+export { readlinkSync, readlink } from "./read_link";
 export { FileInfo, statSync, lstatSync, stat, lstat } from "./stat";
 export { symlinkSync, symlink } from "./symlink";
 export { writeFileSync, writeFile } from "./write_file";
diff --git a/js/read_link.ts b/js/read_link.ts
new file mode 100644
index 000000000..6bd613389
--- /dev/null
+++ b/js/read_link.ts
@@ -0,0 +1,46 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+import * as fbs from "gen/msg_generated";
+import { flatbuffers } from "flatbuffers";
+import { assert } from "./util";
+import * as dispatch from "./dispatch";
+
+/**
+ * Returns the destination of the named symbolic link synchronously.
+ *
+ *     import { readlinkSync } from "deno";
+ *     const targetPath = readlinkSync("symlink/path");
+ */
+export function readlinkSync(name: string): string {
+  return res(dispatch.sendSync(...req(name)));
+}
+
+/**
+ * Returns the destination of the named symbolic link.
+ *
+ *     import { readlink } from "deno";
+ *     const targetPath = await readlink("symlink/path");
+ */
+export async function readlink(name: string): Promise<string> {
+  return res(await dispatch.sendAsync(...req(name)));
+}
+
+function req(
+  name: string
+): [flatbuffers.Builder, fbs.Any, flatbuffers.Offset] {
+  const builder = new flatbuffers.Builder();
+  const name_ = builder.createString(name);
+  fbs.Readlink.startReadlink(builder);
+  fbs.Readlink.addName(builder, name_);
+  const msg = fbs.Readlink.endReadlink(builder);
+  return [builder, fbs.Any.Readlink, msg];
+}
+
+function res(baseRes: null | fbs.Base): string {
+  assert(baseRes !== null);
+  assert(fbs.Any.ReadlinkRes === baseRes!.msgType());
+  const res = new fbs.ReadlinkRes();
+  assert(baseRes!.msg(res) !== null);
+  const path = res.path();
+  assert(path !== null);
+  return path!;
+}
diff --git a/js/read_link_test.ts b/js/read_link_test.ts
new file mode 100644
index 000000000..2df6b30d0
--- /dev/null
+++ b/js/read_link_test.ts
@@ -0,0 +1,44 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+import { test, testPerm, assert, assertEqual } from "./test_util.ts";
+import * as deno from "deno";
+
+testPerm({ write: true }, function readlinkSyncSuccess() {
+  const testDir = deno.makeTempDirSync() + "/test-readlink-sync";
+  const target = testDir + "/target";
+  const symlink = testDir + "/symln";
+  deno.mkdirSync(target);
+  // TODO Add test for Windows once symlink is implemented for Windows.
+  // See https://github.com/denoland/deno/issues/815.
+  if (deno.platform !== "win32") {
+    deno.symlinkSync(target, symlink);
+    const targetPath = deno.readlinkSync(symlink);
+    assertEqual(targetPath, target);
+  }
+});
+
+test(function readlinkSyncNotFound() {
+  let caughtError = false;
+  let data;
+  try {
+    data = deno.readlinkSync("bad_filename");
+  } catch (e) {
+    caughtError = true;
+    assertEqual(e.kind, deno.ErrorKind.NotFound);
+  }
+  assert(caughtError);
+  assertEqual(data, undefined);
+});
+
+testPerm({ write: true }, async function readlinkSuccess() {
+  const testDir = deno.makeTempDirSync() + "/test-readlink";
+  const target = testDir + "/target";
+  const symlink = testDir + "/symln";
+  deno.mkdirSync(target);
+  // TODO Add test for Windows once symlink is implemented for Windows.
+  // See https://github.com/denoland/deno/issues/815.
+  if (deno.platform !== "win32") {
+    deno.symlinkSync(target, symlink);
+    const targetPath = await deno.readlink(symlink);
+    assertEqual(targetPath, target);
+  }
+});
diff --git a/js/unit_tests.ts b/js/unit_tests.ts
index ae9db2a28..578a65c6d 100644
--- a/js/unit_tests.ts
+++ b/js/unit_tests.ts
@@ -11,6 +11,7 @@ import "./mkdir_test.ts";
 import "./make_temp_dir_test.ts";
 import "./stat_test.ts";
 import "./rename_test.ts";
+import "./read_link_test.ts";
 import "./blob_test.ts";
 import "./timers_test.ts";
 import "./symlink_test.ts";