Preserve headers from the root object on expand

There is a bug where, when running an expand query, headers from the
response object get dropped.  These headers include OData.type, and the
newly minted Link header, as well as possible others.

This was actually noted in a TODO, although the author of the TODO,
didn't fully understand the consequences at the time, and thought there
was no functional impact.

To resolve this, this commit resolves the TODO, and allows the Response
object to be moved out, instead of having to create a new one, which
preserves all the response state.  To do this, it creates a move
constructor on the Response object for this use.  The move constructor
is relatively benign, with one caveat, that we might be moving while in
a completion handler (as is the most common use).  So both the existing
operator= and Response() move constructor are amended to handle this
case, and simply null out the response object in the copied object,
which would be correct behavior, given that each callback handler should
only be called once per Response object.

Tested:
curl --insecure --user root:0penBmc -vvvv
https://192.168.7.2/redfish/v1\?\$expand\=\*\(\$levels\=2\)

returns the same body as previously, now with the included:
OData-Version: 4.0
Allow: Get

headers in the response.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: I221364dd4304903b37cacb1386f621b073a0a891

1 files changed, 2 insertions, 0 deletions

diff --git a/include/async_resp.hpp b/include/async_resp.hpp
index 219d9df796..d7f5819142 100644
--- a/include/async_resp.hpp
+++ b/include/async_resp.hpp
@@ -16,6 +16,8 @@ class AsyncResp
 {
   public:
     AsyncResp() = default;
+    explicit AsyncResp(crow::Response&& resIn) : res(std::move(resIn))
+    {}
 
     AsyncResp(const AsyncResp&) = delete;
     AsyncResp(AsyncResp&&) = delete;