Add support for ~user syntax expansion (current user only)

Fixes #1

Author: sindresorhus

index.d.ts

@@ -1,12 +1,18 @@
 /**
 Convert a tilde path to an absolute path: `~/dev` → `/Users/sindresorhus/dev`.
 
+Also expands `~username` when the username matches the current user.
+
 @example
 ```
 import untildify from 'untildify';
 
 untildify('~/dev');
 //=> '/Users/sindresorhus/dev'
+
+// If current user is 'sindresorhus'
+untildify('~sindresorhus/dev');
+//=> '/Users/sindresorhus/dev'
 ```
 */
 export default function untildify(pathWithTilde: string): string;

index.js

@@ -1,11 +1,38 @@
 import os from 'node:os';
 
-const homeDirectory = os.homedir();
+let homeDirectory;
+let currentUser;
 
 export default function untildify(pathWithTilde) {
 	if (typeof pathWithTilde !== 'string') {
 		throw new TypeError(`Expected a string, got ${typeof pathWithTilde}`);
 	}
 
-	return homeDirectory ? pathWithTilde.replace(/^~(?=$|\/|\\)/, homeDirectory) : pathWithTilde;
+	if (homeDirectory === undefined) {
+		homeDirectory = os.homedir();
+	}
+
+	// Handle regular ~ expansion (current user)
+	if (homeDirectory && /^~(?=$|\/|\\)/.test(pathWithTilde)) {
+		return pathWithTilde.replace(/^~/, homeDirectory);
+	}
+
+	// Handle ~username expansion (only for current user)
+	const userMatch = pathWithTilde.match(/^~([^/\\]+)(.*)/);
+	if (userMatch) {
+		if (currentUser === undefined) {
+			currentUser = os.userInfo().username;
+		}
+
+		if (currentUser) {
+			const username = userMatch[1];
+			const rest = userMatch[2];
+			if (username === currentUser) {
+				return homeDirectory + rest;
+			}
+		}
+	}
+
+	// Return unchanged if no expansion occurred
+	return pathWithTilde;
 }

readme.md

@@ -15,8 +15,18 @@ import untildify from 'untildify';
 
 untildify('~/dev');
 //=> '/Users/sindresorhus/dev'
+
+// Assuming the current user is 'sindresorhus'
+untildify('~sindresorhus/dev');
+//=> '/Users/sindresorhus/dev'
 ```
 
+## Features
+
+- Expands `~` to the current user's home directory
+- Expands `~username` to the home directory when username matches the current user
+- Returns path unchanged if username doesn't match the current user
+
 ## Related
 
 See [tildify](https://github.com/sindresorhus/tildify) for the inverse.

test.js

@@ -1,3 +1,4 @@
+import os from 'node:os';
 import test from 'ava';
 import esmock from 'esmock';
 
@@ -49,3 +50,53 @@ test('paths with regex replacement patterns', t => {
 	t.true(expandsTildePrefixWithHome('~/$1'));
 	t.true(expandsTildePrefixWithHome('~/$&'));
 });
+
+// Tests for ~user expansion
+test('~user expansion for current user', async t => {
+	// Use the actual untildify function without mocking for this test
+	const {default: realUntildify} = await import('./index.js');
+	const currentUser = os.userInfo().username;
+	const currentHome = os.homedir();
+
+	// ~currentuser should expand to current user's home
+	t.is(realUntildify(`~${currentUser}`), currentHome);
+	t.is(realUntildify(`~${currentUser}/`), `${currentHome}/`);
+	t.is(realUntildify(`~${currentUser}/dev`), `${currentHome}/dev`);
+});
+
+test('~user expansion for other users', async t => {
+	// Use the actual untildify function without mocking for this test
+	const {default: realUntildify} = await import('./index.js');
+
+	// Other users should return unchanged (simplified implementation)
+	t.is(realUntildify('~root'), '~root');
+	t.is(realUntildify('~root/'), '~root/');
+	t.is(realUntildify('~otheruser/test'), '~otheruser/test');
+});
+
+test('~user expansion for non-existent users', async t => {
+	// Use the actual untildify function without mocking for this test
+	const {default: realUntildify} = await import('./index.js');
+
+	// Non-existent users should return unchanged
+	t.is(realUntildify('~nonexistentuser123'), '~nonexistentuser123');
+	t.is(realUntildify('~nonexistentuser123/'), '~nonexistentuser123/');
+	t.is(realUntildify('~nonexistentuser123/dev'), '~nonexistentuser123/dev');
+});
+
+test('~user expansion edge cases', async t => {
+	// Use the actual untildify function without mocking for this test
+	const {default: realUntildify} = await import('./index.js');
+
+	// Should not expand if not at the beginning
+	t.is(realUntildify('foo~bar'), 'foo~bar');
+	t.is(realUntildify('/~user'), '/~user');
+	t.is(realUntildify('abc~def/ghi'), 'abc~def/ghi');
+
+	// Empty username after ~ (just ~ alone should still work)
+	t.is(realUntildify('~'), os.homedir());
+
+	// Username containing special characters that don't typically appear in usernames
+	t.is(realUntildify('~user!!invalid'), '~user!!invalid');
+	t.is(realUntildify('~user@host'), '~user@host');
+});