From 5b28754602d832f3487d92c5021f879007aece9e Mon Sep 17 00:00:00 2001
From: Jordi Boggiano <j.boggiano@seld.be>
Date: Thu, 10 Nov 2022 16:32:18 +0100
Subject: [PATCH] Avoid normalizing to absolute paths if base dir is /toplevel
 to improve docker portability, fixes #11165, fixes #4404 (#11169)

---
 src/Composer/Util/Filesystem.php            | 19 ++++++++++++++++---
 tests/Composer/Test/Util/FilesystemTest.php |  4 +++-
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/src/Composer/Util/Filesystem.php b/src/Composer/Util/Filesystem.php
index d9f55261b..5bbc5a04e 100644
--- a/src/Composer/Util/Filesystem.php
+++ b/src/Composer/Util/Filesystem.php
@@ -440,7 +440,8 @@ class Filesystem
             $commonPath = strtr(\dirname($commonPath), '\\', '/');
         }
 
-        if (0 !== strpos($from, $commonPath) || '/' === $commonPath) {
+        // no commonality at all
+        if (0 !== strpos($from, $commonPath)) {
             return $to;
         }
 
@@ -448,6 +449,11 @@ class Filesystem
         $sourcePathDepth = substr_count((string) substr($from, \strlen($commonPath)), '/');
         $commonPathCode = str_repeat('../', $sourcePathDepth);
 
+        // allow top level /foo & /bar dirs to be addressed relatively as this is common in Docker setups
+        if ('/' === $commonPath && $sourcePathDepth > 1) {
+            return $to;
+        }
+
         $result = $commonPathCode . substr($to, \strlen($commonPath));
         if (\strlen($result) === 0) {
             return './';
@@ -481,15 +487,22 @@ class Filesystem
             $commonPath = strtr(\dirname($commonPath), '\\', '/');
         }
 
-        if (0 !== strpos($from, $commonPath) || '/' === $commonPath || '.' === $commonPath) {
+        // no commonality at all
+        if (0 !== strpos($from, $commonPath) || '.' === $commonPath) {
             return var_export($to, true);
         }
 
         $commonPath = rtrim($commonPath, '/') . '/';
-        if (strpos($to, $from.'/') === 0) {
+        if (str_starts_with($to, $from.'/')) {
             return '__DIR__ . '.var_export((string) substr($to, \strlen($from)), true);
         }
         $sourcePathDepth = substr_count((string) substr($from, \strlen($commonPath)), '/') + (int) $directories;
+
+        // allow top level /foo & /bar dirs to be addressed relatively as this is common in Docker setups
+        if ('/' === $commonPath && $sourcePathDepth > 1) {
+            return var_export($to, true);
+        }
+
         if ($staticCode) {
             $commonPathCode = "__DIR__ . '".str_repeat('/..', $sourcePathDepth)."'";
         } else {
diff --git a/tests/Composer/Test/Util/FilesystemTest.php b/tests/Composer/Test/Util/FilesystemTest.php
index c738c8e68..e667161cf 100644
--- a/tests/Composer/Test/Util/FilesystemTest.php
+++ b/tests/Composer/Test/Util/FilesystemTest.php
@@ -72,6 +72,7 @@ class FilesystemTest extends TestCase
             ['c:\\bin\\run', 'd:/vendor/acme/bin/run', false, "'D:/vendor/acme/bin/run'"],
             ['/foo/bar', '/foo/bar', true, "__DIR__"],
             ['/foo/bar/', '/foo/bar', true, "__DIR__"],
+            ['/foo', '/baz', true, "dirname(__DIR__).'/baz'"],
             ['/foo/bar', '/foo/baz', true, "dirname(__DIR__).'/baz'"],
             ['/foo/bin/run', '/foo/vendor/acme/bin/run', true, "dirname(dirname(__DIR__)).'/vendor/acme/bin/run'"],
             ['/foo/bin/run', '/bar/bin/run', true, "'/bar/bin/run'"],
@@ -150,7 +151,8 @@ class FilesystemTest extends TestCase
             ['C:/Temp', 'c:\Temp\..\..\test', "../test", true],
             ['C:/Temp/../..', 'c:\Temp\..\..\test', "./test", true],
             ['C:/Temp/../..', 'D:\Temp\..\..\test', "D:/test", true],
-            ['/tmp', '/tmp/../../test', '/test', true],
+            ['/tmp', '/tmp/../../test', '../test', true],
+            ['/tmp', '/test', '../test', true],
             ['/foo/bar', '/foo/bar_vendor', '../bar_vendor', true],
             ['/foo/bar_vendor', '/foo/bar', '../bar', true],
             ['/foo/bar_vendor', '/foo/bar/src', '../bar/src', true],