From 67cbf7f11e0e44663196cdf9e478590f2a957559 Mon Sep 17 00:00:00 2001
From: ydah <13041216+ydah@users.noreply.github.com>
Date: Tue, 28 Jun 2022 17:24:11 +0900
Subject: [PATCH] Add new "Atomic File Operations" rule

When doing file operations after confirming the existence check of a file,
frequent parallel file operations may cause problems that are difficult to reproduce.
Therefore, it is preferable to use atomic file operations.

```ruby
# bad - race condition with another process may result in an error in `mkdir`
unless Dir.exist?(path)
  FileUtils.mkdir(path)
end

# good - atomic and idempotent creation
FileUtils.mkdir_p(path)

# bad - race condition with another process may result in an error in `remove`
if File.exist?(path)
  FileUtils.remove(path)
end

# good - atomic and idempotent removal
FileUtils.rm_f(path)
```
---
 README.adoc | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/README.adoc b/README.adoc
index e43a0e1d..0b590038 100644
--- a/README.adoc
+++ b/README.adoc
@@ -2185,6 +2185,30 @@ File.open('testfile') do |f|
 end
 ----
 
+=== Atomic File Operations [[atomic-file-operations]]
+
+When doing file operations after confirming the existence check of a file, frequent parallel file operations may cause problems that are difficult to reproduce.
+Therefore, it is preferable to use atomic file operations.
+
+[source,ruby]
+----
+# bad - race condition with another process may result in an error in `mkdir`
+unless Dir.exist?(path)
+  FileUtils.mkdir(path)
+end
+
+# good - atomic and idempotent creation
+FileUtils.mkdir_p(path)
+
+# bad - race condition with another process may result in an error in `remove`
+if File.exist?(path)
+  FileUtils.remove(path)
+end
+
+# good - atomic and idempotent removal
+FileUtils.rm_f(path)
+----
+
 === Standard Exceptions [[standard-exceptions]]
 
 Prefer the use of exceptions from the standard library over introducing new exception classes.