net/http: double Content-Length in Response.Write on POST/PUT Request #8180
Description
From golang-dev: """ Matthew Endsley: I was testing the go1.3rc1 release on our codebase and found it failed one of our test cases involving http responses. It appears that in some cases, http.Response.Write will emit 2 Content-Length headers. A short example the reproduces the behavior can be found here: http://play.golang.org/p/qsH1MeVSHu In go 1.2 this generated the following output: HTTP/1.1 200 OK Content-Length: 0 In go1.3rc1 I'm getting the following: HTTP/1.1 200 OK Content-Length: 0 Content-Length: 0 For reference, on current tip (087e446f2c41) I see the same output as go1.3rc1 As a side note, this issue only occurs if response.Request.Method is "POST". If the request method is "GET" the duplicate Content-Length is not emitted. """ The problem was introduced in revision b2ebbbcfc615 for fixing issue #5381. The net/http Server doesn't use this code, but it is a regression from 1.2. In the earlier fix, I didn't take care of the case where PUT/POST were special-cased in transfer.go ages ago in revision 4d792b5bea35 for HTTP Requests, but the transfer code deals with both Requests and Responses, so a Content-Length of length 0 was always being sent for Responses too. That code deserves a second look in Go 1.4, but will fix minimally for now.