Helpers: added findCommonDirectory()

src/Framework/Helpers.php

@@ -36,6 +36,35 @@ public static function purge(string $dir): void
 	}
 
 
+	/**
+	 * Find common directory for given paths. All files or directories must exist.
+	 * @return string  Empty when not found. Slash and back slash chars normalized to DIRECTORY_SEPARATOR.
+	 */
+	public static function findCommonDirectory(array $paths): string
+	{
+		$splitPaths = array_map(function ($s) {
+			$real = realpath($s);
+			if ($s === '') {
+				throw new \RuntimeException("Path must not be empty.");
+			} elseif ($real === false) {
+				throw new \RuntimeException("File or directory '$s' does not exist.");
+			}
+			return explode(DIRECTORY_SEPARATOR, $real);
+		}, $paths);
+
+		$first = (array) array_shift($splitPaths);
+		for ($i = 0; $i < count($first); $i++) {
+			foreach ($splitPaths as $s) {
+				if ($first[$i] !== ($s[$i] ?? null)) {
+					break 2;
+				}
+			}
+		}
+		$common = implode(DIRECTORY_SEPARATOR, array_slice($first, 0, $i));
+		return is_dir($common) ? $common : dirname($common);
+	}
+
+
 	/**
 	 * Parse phpDoc comment.
 	 * @internal

tests/Framework/Helpers.findCommonDirectory.phpt

@@ -0,0 +1,56 @@
+<?php
+
+declare(strict_types=1);
+
+use Tester\Assert;
+use Tester\Helpers;
+
+require __DIR__ . '/../bootstrap.php';
+
+Assert::same('', Helpers::findCommonDirectory([]));
+
+Assert::match(__DIR__ . DIRECTORY_SEPARATOR . 'fixtures.helpers', Helpers::findCommonDirectory([
+	__DIR__ . '/fixtures.helpers/a',
+	__DIR__ . '/fixtures.helpers/aa',
+]));
+
+Assert::match(__DIR__ . DIRECTORY_SEPARATOR . 'fixtures.helpers', Helpers::findCommonDirectory([
+	__DIR__ . '/fixtures.helpers/a/file.txt',
+	__DIR__ . '/fixtures.helpers/aa/file.txt',
+]));
+
+Assert::match(__DIR__ . DIRECTORY_SEPARATOR . 'fixtures.helpers', Helpers::findCommonDirectory([
+	__DIR__ . '/fixtures.helpers/a/',
+	__DIR__ . '/fixtures.helpers/aa/file.txt',
+]));
+
+Assert::match(getcwd(), Helpers::findCommonDirectory([
+	'.',
+]));
+
+Assert::match(dirname(getcwd()), Helpers::findCommonDirectory([
+	'..',
+]));
+
+
+// Root directories always end by directory separator.
+if (is_dir('C:/')) {
+	Assert::match('C:\\', Helpers::findCommonDirectory([
+		'C:',
+	]));
+}
+
+if (is_dir('/')) {
+	Assert::match(realpath('/'), Helpers::findCommonDirectory([  // realpath() - may point to C:\ in Cygwin
+		'/',
+	]));
+}
+
+
+Assert::exception(function () {
+	Helpers::findCommonDirectory(['']);
+}, RuntimeException::class, 'Path must not be empty.');
+
+Assert::exception(function () {
+	Helpers::findCommonDirectory(['does-not-exist']);
+}, RuntimeException::class, "File or directory 'does-not-exist' does not exist.");