add fs/exists (#260)

fs/exists.ts

@@ -0,0 +1,27 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+/**
+ * Test whether or not the given path exists by checking with the file system
+ * @export
+ * @param {string} filePath
+ * @returns {Promise<boolean>}
+ */
+export async function exists(filePath: string): Promise<boolean> {
+  return Deno.stat(filePath)
+    .then(() => true)
+    .catch(() => false);
+}
+
+/**
+ * Test whether or not the given path exists by checking with the file system
+ * @export
+ * @param {string} filePath
+ * @returns {boolean}
+ */
+export function existsSync(filePath: string): boolean {
+  try {
+    Deno.statSync(filePath);
+    return true;
+  } catch {
+    return false;
+  }
+}

fs/exists_test.ts

@@ -0,0 +1,36 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+import { test } from "../testing/mod.ts";
+import { assertEquals } from "../testing/asserts.ts";
+import { exists, existsSync } from "./exists.ts";
+import * as path from "./path/mod.ts";
+
+const testdataDir = path.resolve("fs", "testdata");
+
+test(async function existsFile() {
+  assertEquals(
+    await exists(path.join(testdataDir, "not_exist_file.ts")),
+    false
+  );
+  assertEquals(await existsSync(path.join(testdataDir, "0.ts")), true);
+});
+
+test(function existsFileSync() {
+  assertEquals(existsSync(path.join(testdataDir, "not_exist_file.ts")), false);
+  assertEquals(existsSync(path.join(testdataDir, "0.ts")), true);
+});
+
+test(async function existsDirectory() {
+  assertEquals(
+    await exists(path.join(testdataDir, "not_exist_directory")),
+    false
+  );
+  assertEquals(existsSync(testdataDir), true);
+});
+
+test(function existsDirectorySync() {
+  assertEquals(
+    existsSync(path.join(testdataDir, "not_exist_directory")),
+    false
+  );
+  assertEquals(existsSync(testdataDir), true);
+});

test.ts

@@ -14,6 +14,7 @@ import "./fs/path/test.ts";
 import "./fs/walk_test.ts";
 import "./fs/globrex_test.ts";
 import "./fs/glob_test.ts";
+import "./fs/exists_test.ts";
 import "./io/test.ts";
 import "./http/server_test.ts";
 import "./http/file_server_test.ts";