client.go Simplify default UA logic (#1466)

The getClientName() checks if !NoDefaultUserAgentHeader then returns the Client.Name field.
But it also saves it to atomic field clientName. This is not needed and logic can be simplified.
Previously the clientName vas a byte slice that was copied from c.Name and cached. See 02e0722

Fix #1458

client.go

@@ -788,7 +788,6 @@ type HostClient struct {
 	// Connection pool strategy. Can be either LIFO or FIFO (default).
 	ConnPoolStrategy ConnPoolStrategyType
 
-	clientName  atomic.Value
 	lastUseTime uint32
 
 	connsLock  sync.Mutex
@@ -1327,9 +1326,14 @@ func (c *HostClient) doNonNilReqResp(req *Request, resp *Response) (bool, error)
 
 	userAgentOld := req.Header.UserAgent()
 	if len(userAgentOld) == 0 {
-		req.Header.userAgent = append(req.Header.userAgent[:0], c.getClientName()...)
+		userAgent := c.Name
+		if userAgent == "" && !c.NoDefaultUserAgentHeader {
+			userAgent = defaultUserAgent
+		}
+		if userAgent != "" {
+			req.Header.userAgent = append(req.Header.userAgent[:], userAgent...)
+		}
 	}
-
 	if c.Transport != nil {
 		err := c.Transport(req, resp)
 		return err == nil, err
@@ -1990,21 +1994,6 @@ func dialAddr(addr string, dial DialFunc, dialDualStack, isTLS bool, tlsConfig *
 	return conn, nil
 }
 
-func (c *HostClient) getClientName() []byte {
-	v := c.clientName.Load()
-	var clientName []byte
-	if v == nil {
-		clientName = []byte(c.Name)
-		if len(clientName) == 0 && !c.NoDefaultUserAgentHeader {
-			clientName = defaultUserAgent
-		}
-		c.clientName.Store(clientName)
-	} else {
-		clientName = v.([]byte)
-	}
-	return clientName
-}
-
 // AddMissingPort adds a port to a host if it is missing.
 // A literal IPv6 address in hostport must be enclosed in square
 // brackets, as in "[::1]:80", "[::1%lo0]:80".
@@ -2318,7 +2307,6 @@ type pipelineConnClient struct {
 
 	tlsConfigLock sync.Mutex
 	tlsConfig     *tls.Config
-	clientName    atomic.Value
 }
 
 type pipelineWork struct {
@@ -2389,7 +2377,13 @@ func (c *pipelineConnClient) DoDeadline(req *Request, resp *Response, deadline t
 
 	userAgentOld := req.Header.UserAgent()
 	if len(userAgentOld) == 0 {
-		req.Header.userAgent = append(req.Header.userAgent[:0], c.getClientName()...)
+		userAgent := c.Name
+		if userAgent == "" && !c.NoDefaultUserAgentHeader {
+			userAgent = defaultUserAgent
+		}
+		if userAgent != "" {
+			req.Header.userAgent = append(req.Header.userAgent[:], userAgent...)
+		}
 	}
 
 	w := c.acquirePipelineWork(timeout)
@@ -2490,7 +2484,13 @@ func (c *pipelineConnClient) Do(req *Request, resp *Response) error {
 
 	userAgentOld := req.Header.UserAgent()
 	if len(userAgentOld) == 0 {
-		req.Header.userAgent = append(req.Header.userAgent[:0], c.getClientName()...)
+		userAgent := c.Name
+		if userAgent == "" && !c.NoDefaultUserAgentHeader {
+			userAgent = defaultUserAgent
+		}
+		if userAgent != "" {
+			req.Header.userAgent = append(req.Header.userAgent[:], userAgent...)
+		}
 	}
 
 	w := c.acquirePipelineWork(0)
@@ -2886,19 +2886,4 @@ func (c *pipelineConnClient) PendingRequests() int {
 	return n
 }
 
-func (c *pipelineConnClient) getClientName() []byte {
-	v := c.clientName.Load()
-	var clientName []byte
-	if v == nil {
-		clientName = []byte(c.Name)
-		if len(clientName) == 0 && !c.NoDefaultUserAgentHeader {
-			clientName = defaultUserAgent
-		}
-		c.clientName.Store(clientName)
-	} else {
-		clientName = v.([]byte)
-	}
-	return clientName
-}
-
 var errPipelineConnStopped = errors.New("pipeline connection has been stopped")

client_test.go

@@ -724,7 +724,7 @@ func TestClientDefaultUserAgent(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if userAgentSeen != string(defaultUserAgent) {
+	if userAgentSeen != defaultUserAgent {
 		t.Fatalf("User-Agent defers %q != %q", userAgentSeen, defaultUserAgent)
 	}
 }

strings.go

@@ -2,7 +2,7 @@ package fasthttp
 
 var (
 	defaultServerName  = []byte("fasthttp")
-	defaultUserAgent   = []byte("fasthttp")
+	defaultUserAgent   = "fasthttp"
 	defaultContentType = []byte("text/plain; charset=utf-8")
 )