FG-277: correctly handle the leading slash

packages/fs/fs.scandir/src/providers/async.ts

@@ -5,6 +5,7 @@ import { IS_SUPPORT_READDIR_WITH_FILE_TYPES } from '../constants';
 import Settings from '../settings';
 import { Entry, Stats } from '../types';
 import * as utils from '../utils';
+import * as common from './common';
 
 type RplTaskStats = rpl.Task<Stats>;
 type RplTaskEntry = rpl.Task<Entry>;
@@ -30,7 +31,7 @@ export function readdirWithFileTypes(directory: string, settings: Settings, call
 		const entries: Entry[] = dirents.map((dirent) => ({
 			dirent,
 			name: dirent.name,
-			path: `${directory}${settings.pathSegmentSeparator}${dirent.name}`
+			path: common.joinPathSegments(directory, dirent.name, settings.pathSegmentSeparator)
 		}));
 
 		if (!settings.followSymbolicLinks) {
@@ -77,7 +78,7 @@ export function readdir(directory: string, settings: Settings, callback: AsyncCa
 			return callFailureCallback(callback, readdirError);
 		}
 
-		const filepaths = names.map((name) => `${directory}${settings.pathSegmentSeparator}${name}`);
+		const filepaths = names.map((name) => common.joinPathSegments(directory, name, settings.pathSegmentSeparator));
 
 		const tasks: RplTaskStats[] = filepaths.map((filepath): RplTaskStats => {
 			return (done) => fsStat.stat(filepath, settings.fsStatSettings, done);

packages/fs/fs.scandir/src/providers/common.spec.ts

@@ -0,0 +1,24 @@
+import * as assert from 'assert';
+
+import * as common from './common';
+
+describe('Readers → Common', () => {
+	describe('.joinPathSegments', () => {
+		it('should return concatenated string', () => {
+			assert.strictEqual(common.joinPathSegments('.', 'a', '/'), './a');
+		});
+
+		it('should return correct string when the first segment ens with the separator symbol', () => {
+			// Unix
+			assert.strictEqual(common.joinPathSegments('/', 'a', '/'), '/a');
+			assert.strictEqual(common.joinPathSegments('//', 'a', '/'), '//a');
+			assert.strictEqual(common.joinPathSegments('/a/', 'b', '/'), '/a/b');
+
+			// Windows
+			assert.strictEqual(common.joinPathSegments('C:/', 'Users', '/'), 'C:/Users');
+			assert.strictEqual(common.joinPathSegments('C:\\', 'Users', '\\'), 'C:\\Users');
+			assert.strictEqual(common.joinPathSegments('//?/C:/', 'Users', '/'), '//?/C:/Users');
+			assert.strictEqual(common.joinPathSegments('\\\\?\\C:\\', 'Users', '\\'), '\\\\?\\C:\\Users');
+		});
+	});
+});

packages/fs/fs.scandir/src/providers/common.ts

@@ -0,0 +1,10 @@
+export function joinPathSegments(a: string, b: string, separator: string): string {
+	/**
+	 * The correct handling of cases when the first segment is a root (`/`, `C:/`) or UNC path (`//?/C:/`).
+	 */
+	if (a.endsWith(separator)) {
+		return a + b;
+	}
+
+	return a + separator + b;
+}

packages/fs/fs.scandir/src/providers/sync.ts

@@ -4,6 +4,7 @@ import { IS_SUPPORT_READDIR_WITH_FILE_TYPES } from '../constants';
 import Settings from '../settings';
 import { Entry } from '../types';
 import * as utils from '../utils';
+import * as common from './common';
 
 export function read(directory: string, settings: Settings): Entry[] {
 	if (!settings.stats && IS_SUPPORT_READDIR_WITH_FILE_TYPES) {
@@ -20,7 +21,7 @@ export function readdirWithFileTypes(directory: string, settings: Settings): Ent
 		const entry: Entry = {
 			dirent,
 			name: dirent.name,
-			path: `${directory}${settings.pathSegmentSeparator}${dirent.name}`
+			path: common.joinPathSegments(directory, dirent.name, settings.pathSegmentSeparator)
 		};
 
 		if (entry.dirent.isSymbolicLink() && settings.followSymbolicLinks) {
@@ -43,7 +44,7 @@ export function readdir(directory: string, settings: Settings): Entry[] {
 	const names = settings.fs.readdirSync(directory);
 
 	return names.map((name) => {
-		const entryPath = `${directory}${settings.pathSegmentSeparator}${name}`;
+		const entryPath = common.joinPathSegments(directory, name, settings.pathSegmentSeparator);
 		const stats = fsStat.statSync(entryPath, settings.fsStatSettings);
 
 		const entry: Entry = {