From e829ff80bc7312d7fa70fbd7be441863eb6dcc61 Mon Sep 17 00:00:00 2001
From: Ilya Urvachev <rtm@ctrlz.ru>
Date: Tue, 29 Dec 2020 23:57:29 +0300
Subject: [PATCH 1/3] feat(Cache): make cache writes more atomic

Fixes #9568
---
 src/Composer/Cache.php | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/Composer/Cache.php b/src/Composer/Cache.php
index c4bb4b2eb..df45e66ed 100644
--- a/src/Composer/Cache.php
+++ b/src/Composer/Cache.php
@@ -115,7 +115,8 @@ class Cache
             $this->io->writeError('Writing '.$this->root . $file.' into cache', true, IOInterface::DEBUG);
 
             try {
-                return file_put_contents($this->root . $file.'.tmp', $contents) !== false && rename($this->root . $file . '.tmp', $this->root . $file);
+                $tempFileName = $this->root . $file . uniqid('.tmp.', true);
+                return file_put_contents($tempFileName, $contents) !== false && rename($tempFileName, $this->root . $file);
             } catch (\ErrorException $e) {
                 $this->io->writeError('<warning>Failed to write into cache: '.$e->getMessage().'</warning>', true, IOInterface::DEBUG);
                 if (preg_match('{^file_put_contents\(\): Only ([0-9]+) of ([0-9]+) bytes written}', $e->getMessage(), $m)) {

From ab6e0fa9611ddd6f25e311018b205e1c659a5717 Mon Sep 17 00:00:00 2001
From: Ilya Urvachev <rtm@ctrlz.ru>
Date: Wed, 6 Jan 2021 02:17:34 +0300
Subject: [PATCH 2/3] use `.tmp` extension for temporary files

also updated `catch` block to use temporary filename
---
 src/Composer/Cache.php | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/Composer/Cache.php b/src/Composer/Cache.php
index df45e66ed..fe2b97c59 100644
--- a/src/Composer/Cache.php
+++ b/src/Composer/Cache.php
@@ -114,21 +114,21 @@ class Cache
 
             $this->io->writeError('Writing '.$this->root . $file.' into cache', true, IOInterface::DEBUG);
 
+            $tempFileName = $this->root . $file . uniqid('.', true) . '.tmp';
             try {
-                $tempFileName = $this->root . $file . uniqid('.tmp.', true);
                 return file_put_contents($tempFileName, $contents) !== false && rename($tempFileName, $this->root . $file);
             } catch (\ErrorException $e) {
                 $this->io->writeError('<warning>Failed to write into cache: '.$e->getMessage().'</warning>', true, IOInterface::DEBUG);
                 if (preg_match('{^file_put_contents\(\): Only ([0-9]+) of ([0-9]+) bytes written}', $e->getMessage(), $m)) {
                     // Remove partial file.
-                    unlink($this->root . $file);
+                    unlink($tempFileName);
 
                     $message = sprintf(
                         '<warning>Writing %1$s into cache failed after %2$u of %3$u bytes written, only %4$u bytes of free space available</warning>',
-                        $this->root . $file,
+                        $tempFileName,
                         $m[1],
                         $m[2],
-                        @disk_free_space($this->root . dirname($file))
+                        @disk_free_space($this->root . dirname($tempFileName))
                     );
 
                     $this->io->writeError($message);

From cee8e3e3b7f9239d3f66b489ae10b8f73cb6b7e0 Mon Sep 17 00:00:00 2001
From: Ilya Urvachev <rtm@ctrlz.ru>
Date: Wed, 6 Jan 2021 15:21:45 +0300
Subject: [PATCH 3/3] fix `dirname` usage

---
 src/Composer/Cache.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Composer/Cache.php b/src/Composer/Cache.php
index fe2b97c59..9590693ff 100644
--- a/src/Composer/Cache.php
+++ b/src/Composer/Cache.php
@@ -128,7 +128,7 @@ class Cache
                         $tempFileName,
                         $m[1],
                         $m[2],
-                        @disk_free_space($this->root . dirname($tempFileName))
+                        @disk_free_space(dirname($tempFileName))
                     );
 
                     $this->io->writeError($message);