From cb0cde7337489afd6915277c5871c96f8f81e1bb Mon Sep 17 00:00:00 2001
From: Chris Prather <chris@prather.org>
Date: Thu, 29 Oct 2020 03:44:19 -0400
Subject: [PATCH] Skip decoding if Content-Length is zero (#63)

* Some servers send a 0 length response, without a 204 StatusNoContent. Skip decoding these responses, as if they're 204s

Co-authored-by: Dalton Hubble <dghubble@gmail.com>
---
 sling.go      | 15 ++++++++-------
 sling_test.go | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/sling.go b/sling.go
index 889407d..797b7fe 100644
--- a/sling.go
+++ b/sling.go
@@ -360,9 +360,9 @@ func (s *Sling) ReceiveSuccess(successV interface{}) (*http.Response, error) {
 // Receive creates a new HTTP request and returns the response. Success
 // responses (2XX) are JSON decoded into the value pointed to by successV and
 // other responses are JSON decoded into the value pointed to by failureV.
-// If the status code of response is 204(no content), decoding is skipped.
-// Any error creating the request, sending it, or decoding the response is
-// returned.
+// If the status code of response is 204(no content) or the Content-Lenght is 0,
+// decoding is skipped. Any error creating the request, sending it, or decoding
+// the response is returned.
 // Receive is shorthand for calling Request and Do.
 func (s *Sling) Receive(successV, failureV interface{}) (*http.Response, error) {
 	req, err := s.Request()
@@ -375,8 +375,9 @@ func (s *Sling) Receive(successV, failureV interface{}) (*http.Response, error)
 // Do sends an HTTP request and returns the response. Success responses (2XX)
 // are JSON decoded into the value pointed to by successV and other responses
 // are JSON decoded into the value pointed to by failureV.
-// If the status code of response is 204(no content), decoding is skipped.
-// Any error sending the request or decoding the response is returned.
+// If the status code of response is 204(no content) or the Content-Length is 0,
+// decoding is skipped. Any error sending the request or decoding the response
+// is returned.
 func (s *Sling) Do(req *http.Request, successV, failureV interface{}) (*http.Response, error) {
 	resp, err := s.httpClient.Do(req)
 	if err != nil {
@@ -391,8 +392,8 @@ func (s *Sling) Do(req *http.Request, successV, failureV interface{}) (*http.Res
 	// See: https://golang.org/pkg/net/http/#Response
 	defer io.Copy(ioutil.Discard, resp.Body)
 
-	// Don't try to decode on 204s
-	if resp.StatusCode == http.StatusNoContent {
+	// Don't try to decode on 204s or Content-Length is 0
+	if resp.StatusCode == http.StatusNoContent || resp.ContentLength == 0 {
 		return resp, nil
 	}
 
diff --git a/sling_test.go b/sling_test.go
index 132edec..aca29aa 100644
--- a/sling_test.go
+++ b/sling_test.go
@@ -828,6 +828,38 @@ func TestReceive_success(t *testing.T) {
 	}
 }
 
+func TestReceive_StatusOKNoContent(t *testing.T) {
+	client, mux, server := testServer()
+	defer server.Close()
+	mux.HandleFunc("/foo/submit", func(w http.ResponseWriter, r *http.Request) {
+		assertMethod(t, "POST", r)
+		w.WriteHeader(201)
+		w.Header().Set("Location", "/foo/latest")
+	})
+
+	endpoint := New().Client(client).Base("http://example.com/").Path("foo/").Post("submit")
+	// fake a post response for testing purposes, checking that it's valid happens in other tests
+	params := FakeParams{}
+	model := new(FakeModel)
+	apiError := new(APIError)
+	resp, err := endpoint.New().BodyForm(params).Receive(model, apiError)
+
+	if err != nil {
+		t.Errorf("expected nil, got %v", err)
+	}
+	if resp.StatusCode != 201 {
+		t.Errorf("expected %d, got %d", 201, resp.StatusCode)
+	}
+	expectedModel := &FakeModel{}
+	if !reflect.DeepEqual(expectedModel, model) {
+		t.Errorf("expected %v, got %v", expectedModel, model)
+	}
+	expectedAPIError := &APIError{}
+	if !reflect.DeepEqual(expectedAPIError, apiError) {
+		t.Errorf("failureV should be zero valued, exepcted %v, got %v", expectedAPIError, apiError)
+	}
+}
+
 func TestReceive_failure(t *testing.T) {
 	client, mux, server := testServer()
 	defer server.Close()