From db922514f49bbc8756a55da3cffe5ed5c0463bee Mon Sep 17 00:00:00 2001
From: Samuel Williams <samuel.williams@oriontransfer.co.nz>
Date: Sat, 11 Jan 2020 10:08:56 +1300
Subject: [PATCH] Fix ActiveStorage use-case and add test case. Fixes #1464.

---
 lib/rack/files.rb  |  2 +-
 test/spec_files.rb | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/lib/rack/files.rb b/lib/rack/files.rb
index 20f048e44..f1a91c8bc 100644
--- a/lib/rack/files.rb
+++ b/lib/rack/files.rb
@@ -22,7 +22,7 @@ class Files
     attr_reader :root
 
     def initialize(root, headers = {}, default_mime = 'text/plain')
-      @root = ::File.expand_path root
+      @root = (::File.expand_path(root) if root)
       @headers = headers
       @default_mime = default_mime
       @head = Rack::Head.new(lambda { |env| get env })
diff --git a/test/spec_files.rb b/test/spec_files.rb
index ad57972d2..6e75c073a 100644
--- a/test/spec_files.rb
+++ b/test/spec_files.rb
@@ -12,6 +12,20 @@ def files(*args)
     Rack::Lint.new Rack::Files.new(*args)
   end
 
+  it "can be used without root" do
+    # https://github.com/rack/rack/issues/1464
+
+    app = Rack::Files.new(nil)
+
+    request = Rack::Request.new(
+      Rack::MockRequest.env_for("/cgi/test")
+    )
+    
+    file_path = File.expand_path("cgi/test", __dir__)
+    status, headers, body = app.serving(request, file_path)
+    assert_equal 200, status
+  end
+
   it 'serves files with + in the file name' do
     Dir.mktmpdir do |dir|
       File.write File.join(dir, "you+me.txt"), "hello world"