Don't create empty tempfile if no file was selected

lib/rack/utils.rb

@@ -291,7 +291,10 @@ def self.parse_multipart(env)
               content_length = -1  if $1 == "--"
             end
 
-            if filename
+            if filename == ""
+              # filename is blank which means no file has been selected
+              data = nil
+            elsif filename
               body.rewind
 
               # Take the basename of the upload's original filename.

test/multipart/empty

@@ -0,0 +1,10 @@
+--AaB03x
+Content-Disposition: form-data; name="submit-name"
+
+Larry
+--AaB03x
+Content-Disposition: form-data; name="files"; filename="file1.txt"
+Content-Type: text/plain
+
+
+--AaB03x--

test/multipart/none

@@ -0,0 +1,9 @@
+--AaB03x
+Content-Disposition: form-data; name="submit-name"
+
+Larry
+--AaB03x
+Content-Disposition: form-data; name="files"; filename=""
+
+
+--AaB03x--

test/spec_rack_utils.rb

@@ -184,6 +184,26 @@ def context env, app=@app; app.call(env); end
     params["files"][:tempfile].read.length.should.equal 26473
   end
 
+  specify "should parse multipart upload with empty file" do
+    env = Rack::MockRequest.env_for("/", multipart_fixture(:empty))
+    params = Rack::Utils::Multipart.parse_multipart(env)
+    params["submit-name"].should.equal "Larry"
+    params["files"][:type].should.equal "text/plain"
+    params["files"][:filename].should.equal "file1.txt"
+    params["files"][:head].should.equal "Content-Disposition: form-data; " +
+      "name=\"files\"; filename=\"file1.txt\"\r\n" +
+      "Content-Type: text/plain\r\n"
+    params["files"][:name].should.equal "files"
+    params["files"][:tempfile].read.should.equal ""
+  end
+
+  specify "should not create empty an tempfile if no file was selected" do
+    env = Rack::MockRequest.env_for("/", multipart_fixture(:none))
+    params = Rack::Utils::Multipart.parse_multipart(env)
+    params["submit-name"].should.equal "Larry"
+    params["files"].should.equal nil
+  end
+
   specify "should parse IE multipart upload and clean up filename" do
     env = Rack::MockRequest.env_for("/", multipart_fixture(:ie))
     params = Rack::Utils::Multipart.parse_multipart(env)