Fix unexpected panic when calling Do of a PipelineClient (#997)

* fix: Unexpected panic for PipelineClient

PipelineClient would panic when calling `Do` with a nil Response as
the second parm

This commit fixes the unexpected panic by checking nil first before
setting fields for Response

* Add tests to ensure nil resp is valid for PipelineClient

client.go

@@ -1443,8 +1443,7 @@ var (
 		"Make sure the server returns 'Connection: close' response header before closing the connection")
 )
 
-type timeoutError struct {
-}
+type timeoutError struct{}
 
 func (e *timeoutError) Error() string {
 	return "timeout"
@@ -1458,10 +1457,8 @@ func (e *timeoutError) Timeout() bool {
 	return true
 }
 
-var (
-	// ErrTimeout is returned from timed out calls.
-	ErrTimeout = &timeoutError{}
-)
+// ErrTimeout is returned from timed out calls.
+var ErrTimeout = &timeoutError{}
 
 // SetMaxConns sets up the maximum number of connections which may be established to all hosts listed in Addr.
 func (c *HostClient) SetMaxConns(newMaxConns int) {
@@ -1571,7 +1568,6 @@ func (c *HostClient) queueForIdle(w *wantConn) {
 
 func (c *HostClient) dialConnFor(w *wantConn) {
 	conn, err := c.dialHostHard()
-
 	if err != nil {
 		w.tryDeliver(nil, err)
 		c.decConnsCount()
@@ -1690,7 +1686,6 @@ func (c *HostClient) decConnsCount() {
 	if !dialed {
 		c.connsCount--
 	}
-
 }
 
 // ConnsCount returns connection count of HostClient
@@ -2078,15 +2073,13 @@ func (q *wantConnQueue) popFront() *wantConn {
 
 // peekFront returns the wantConn at the front of the queue without removing it.
 func (q *wantConnQueue) peekFront() *wantConn {
-
 	if q.headPos < len(q.head) {
 		return q.head[q.headPos]
 	}
 	if len(q.tail) > 0 {
 		return q.tail[0]
 	}
 	return nil
-
 }
 
 // cleanFront pops any wantConns that are no longer waiting from the head of the
@@ -2389,8 +2382,6 @@ func (c *PipelineClient) Do(req *Request, resp *Response) error {
 func (c *pipelineConnClient) Do(req *Request, resp *Response) error {
 	c.init()
 
-	resp.Header.disableNormalizing = c.DisableHeaderNamesNormalizing
-
 	if c.DisablePathNormalizing {
 		req.URI().DisablePathNormalizing = true
 	}
@@ -2403,6 +2394,7 @@ func (c *pipelineConnClient) Do(req *Request, resp *Response) error {
 	w := acquirePipelineWork(&c.workPool, 0)
 	w.req = req
 	if resp != nil {
+		resp.Header.disableNormalizing = c.DisableHeaderNamesNormalizing
 		w.resp = resp
 	} else {
 		w.resp = &w.respCopy

client_test.go

@@ -305,6 +305,34 @@ func TestClientNilResp(t *testing.T) {
 	}
 }
 
+func TestPipelineClientNilResp(t *testing.T) {
+	t.Parallel()
+
+	ln := fasthttputil.NewInmemoryListener()
+	s := &Server{
+		Handler: func(ctx *RequestCtx) {
+		},
+	}
+	go s.Serve(ln) //nolint:errcheck
+	c := &PipelineClient{
+		Dial: func(addr string) (net.Conn, error) {
+			return ln.Dial()
+		},
+	}
+	req := AcquireRequest()
+	req.Header.SetMethod(MethodGet)
+	req.SetRequestURI("http://example.com")
+	if err := c.Do(req, nil); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.DoTimeout(req, nil, time.Second); err != nil {
+		t.Fatal(err)
+	}
+	if err := c.DoDeadline(req, nil, time.Now().Add(time.Second)); err != nil {
+		t.Fatal(err)
+	}
+}
+
 func TestClientParseConn(t *testing.T) {
 	t.Parallel()
 
@@ -337,7 +365,6 @@ func TestClientParseConn(t *testing.T) {
 	if !regexp.MustCompile(`^127\.0\.0\.1:[0-9]{4,5}$`).MatchString(res.LocalAddr().String()) {
 		t.Fatalf("res LocalAddr addr match fail: %s, hope match: %s", res.LocalAddr().String(), "^127.0.0.1:[0-9]{4,5}$")
 	}
-
 }
 
 func TestClientPostArgs(t *testing.T) {
@@ -419,7 +446,6 @@ func TestClientRedirectSameSchema(t *testing.T) {
 		t.Fatalf("HostClient error code response %d", statusCode)
 		return
 	}
-
 }
 
 func TestClientRedirectClientChangingSchemaHttp2Https(t *testing.T) {
@@ -2601,7 +2627,6 @@ func TestHostClientMaxConnWaitTimeoutError(t *testing.T) {
 					t.Errorf("unexpected body %q. Expecting %q", body, "abcd")
 				}
 			}
-
 		}()
 	}
 	wg.Wait()
@@ -2694,7 +2719,6 @@ func TestHostClientMaxConnWaitTimeoutWithEarlierDeadline(t *testing.T) {
 					t.Errorf("unexpected body %q. Expecting %q", body, "abcd")
 				}
 			}
-
 		}()
 	}
 	wg.Wait()