Add fallback username for Docker run environment (#22)

Co-authored-by: Sindre Sorhus <[email protected]>

index.js

@@ -24,6 +24,8 @@ const getUsernameFromOsUserInfo = () => {
 
 const cleanWindowsCommand = string => string.replace(/^.*\\/, '');
 
+const makeUsernameFromId = userId => `no-username-${userId}`;
+
 module.exports = mem(async () => {
 	const envVariable = getEnvironmentVariable();
 	if (envVariable) {
@@ -35,12 +37,20 @@ module.exports = mem(async () => {
 		return userInfoUsername;
 	}
 
+	/**
+	First we try to get the ID of the user and then the actual username. We do this because in `docker run --user <uid>:<gid>` context, we don't have "username" available. Therefore, we have a fallback to `makeUsernameFromId` for such scenario. Applies also to the `sync()` method below.
+	*/
 	try {
 		if (process.platform === 'win32') {
 			return cleanWindowsCommand(await execa.stdout('whoami'));
 		}
 
-		return await execa.stdout('id', ['-un']);
+		const userId = await execa.stdout('id', ['-u']);
+		try {
+			return await execa.stdout('id', ['-un', userId]);
+		} catch (_) {}
+
+		return makeUsernameFromId(userId);
 	} catch (_) {}
 });
 
@@ -60,6 +70,11 @@ module.exports.sync = mem(() => {
 			return cleanWindowsCommand(execa.sync('whoami').stdout);
 		}
 
-		return execa.sync('id', ['-un']).stdout;
+		const userId = execa.sync('id', ['-u']).stdout;
+		try {
+			return execa.sync('id', ['-un', userId]).stdout;
+		} catch (_) {}
+
+		return makeUsernameFromId(userId);
 	} catch (_) {}
 });