fix: enforce content length header when body is nil and client specifies SetContentLength true (go-resty#1003)

* fix: only override nil body if valid http verb

* test: add testcase validating http server receives correct Content-Length Header

* fix: update Test_parseRequestBody to accommodate nil body request with SetContentLength override scenario

* fix: remove redundant conditional check

---------

Co-authored-by: Jeevanandam M. <jeeva@myjeeva.com>

Author: Libero-Dev

middleware.go

@@ -196,6 +196,10 @@ func parseRequestBody(c *Client, r *Request) error {
 			}
 		case len(c.FormData) > 0 || len(r.FormData) > 0: // Handling Form Data
 			handleFormData(c, r)
+		case r.Body == nil && r.bodyBuf == nil: // Handling Request body when nil body
+			// Go http library omits Content-Length if body is nil; use http.NoBody to force it if SetContentLength is true
+			r.Body = http.NoBody
+			fallthrough
 		case r.Body != nil: // Handling Request body
 			handleContentType(c, r)
 
@@ -315,6 +319,7 @@ func createCurlCmd(c *Client, r *Request) (err error) {
 		}
 		*r.resultCurlCmd = buildCurlRequest(r.RawRequest, c.httpClient.Jar)
 	}
+
 	return nil
 }
 

middleware_test.go

@@ -513,13 +513,15 @@ func Test_parseRequestBody(t *testing.T) {
 				r.SetContentLength(true)
 			},
 			expectedContentLength: "0",
+			expectedBodyBuf:       []byte{},
 		},
 		{
 			name: "empty body with SetContentLength by client",
 			init: func(c *Client, r *Request) {
 				c.SetContentLength(true)
 			},
 			expectedContentLength: "0",
+			expectedBodyBuf:       []byte{},
 		},
 		{
 			name: "string body",

request_test.go

@@ -2283,3 +2283,27 @@ func TestRequestGH917(t *testing.T) {
 	}
 	wg.Wait()
 }
+
+func TestSetContentLengthTrueWithNilBody(t *testing.T) {
+	ts := createPostServer(t)
+	defer ts.Close()
+
+	c := dc()
+
+	c.OnBeforeRequest(func(client *Client, request *Request) error {
+		request.
+			SetBody(nil).
+			SetContentLength(true)
+
+		return nil
+	})
+
+	c = c.SetBaseURL(ts.URL)
+
+	resp, err := c.R().Execute("POST", "/check-request-content-length")
+
+	assertNil(t, err)
+
+	// when body is nil and SetContentLength is true expect Content-Length == "0"
+	assertEqual(t, "0", resp.Header().Get("Request-Content-Length"))
+}

resty_test.go

@@ -326,6 +326,10 @@ func createPostServer(t *testing.T) *httptest.Server {
 				}
 				http.SetCookie(w, &cookie)
 				w.WriteHeader(http.StatusOK)
+			case "/check-request-content-length":
+				// test endpoint for checking the server receives the correct Content-Length Header from a request
+				w.Header().Add("Request-Content-Length", r.Header.Get("Content-Length"))
+				w.WriteHeader(http.StatusOK)
 			}
 		}
 	})