caddyhttp: support unix sockets in caddy respond command (#6010)

previously the `caddy respond` command would treat the argument
passed to --listen as a TCP socket address, iterating over a possible
port range.

this patch factors the server creation out into a separate function,
allowing this to be reused in case the listen address is a unix network
address.

modules/caddyhttp/staticresp.go

@@ -257,6 +257,53 @@ func (s StaticResponse) ServeHTTP(w http.ResponseWriter, r *http.Request, next H
 	return nil
 }
 
+func buildHTTPServer(i int, port uint, addr string, statusCode int, hdr http.Header, body string, accessLog bool) (*Server, error) {
+	var handlers []json.RawMessage
+
+	// response body supports a basic template; evaluate it
+	tplCtx := struct {
+		N       int    // server number
+		Port    uint   // only the port
+		Address string // listener address
+	}{
+		N:       i,
+		Port:    port,
+		Address: addr,
+	}
+	tpl, err := template.New("body").Parse(body)
+	if err != nil {
+		return nil, err
+	}
+	buf := new(bytes.Buffer)
+	err = tpl.Execute(buf, tplCtx)
+	if err != nil {
+		return nil, err
+	}
+
+	// create route with handler
+	handler := StaticResponse{
+		StatusCode: WeakString(fmt.Sprintf("%d", statusCode)),
+		Headers:    hdr,
+		Body:       buf.String(),
+	}
+	handlers = append(handlers, caddyconfig.JSONModuleObject(handler, "handler", "static_response", nil))
+	route := Route{HandlersRaw: handlers}
+
+	server := &Server{
+		Listen:            []string{addr},
+		ReadHeaderTimeout: caddy.Duration(10 * time.Second),
+		IdleTimeout:       caddy.Duration(30 * time.Second),
+		MaxHeaderBytes:    1024 * 10,
+		Routes:            RouteList{route},
+		AutoHTTPS:         &AutoHTTPSConfig{DisableRedir: true},
+	}
+	if accessLog {
+		server.Logs = new(ServerLogConfig)
+	}
+
+	return server, nil
+}
+
 func cmdRespond(fl caddycmd.Flags) (int, error) {
 	caddy.TrapSignals()
 
@@ -332,66 +379,39 @@ func cmdRespond(fl caddycmd.Flags) (int, error) {
 		hdr.Set(key, val)
 	}
 
+	// build each HTTP server
+	httpApp := App{Servers: make(map[string]*Server)}
+
 	// expand listen address, if more than one port
 	listenAddr, err := caddy.ParseNetworkAddress(listen)
 	if err != nil {
 		return caddy.ExitCodeFailedStartup, err
 	}
+
+	if !listenAddr.IsUnixNetwork() {
 		listenAddrs := make([]string, 0, listenAddr.PortRangeSize())
 		for offset := uint(0); offset < listenAddr.PortRangeSize(); offset++ {
 			listenAddrs = append(listenAddrs, listenAddr.JoinHostPort(offset))
 		}
 
-	// build each HTTP server
-	httpApp := App{Servers: make(map[string]*Server)}
-
 		for i, addr := range listenAddrs {
-		var handlers []json.RawMessage
-
-		// response body supports a basic template; evaluate it
-		tplCtx := struct {
-			N       int    // server number
-			Port    uint   // only the port
-			Address string // listener address
-		}{
-			N:       i,
-			Port:    listenAddr.StartPort + uint(i),
-			Address: addr,
-		}
-		tpl, err := template.New("body").Parse(body)
+			server, err := buildHTTPServer(i, listenAddr.StartPort+uint(i), addr, statusCode, hdr, body, accessLog)
 			if err != nil {
 				return caddy.ExitCodeFailedStartup, err
 			}
-		buf := new(bytes.Buffer)
-		err = tpl.Execute(buf, tplCtx)
-		if err != nil {
-			return caddy.ExitCodeFailedStartup, err
-		}
-
-		// create route with handler
-		handler := StaticResponse{
-			StatusCode: WeakString(fmt.Sprintf("%d", statusCode)),
-			Headers:    hdr,
-			Body:       buf.String(),
-		}
-		handlers = append(handlers, caddyconfig.JSONModuleObject(handler, "handler", "static_response", nil))
-		route := Route{HandlersRaw: handlers}
-
-		server := &Server{
-			Listen:            []string{addr},
-			ReadHeaderTimeout: caddy.Duration(10 * time.Second),
-			IdleTimeout:       caddy.Duration(30 * time.Second),
-			MaxHeaderBytes:    1024 * 10,
-			Routes:            RouteList{route},
-			AutoHTTPS:         &AutoHTTPSConfig{DisableRedir: true},
-		}
-		if accessLog {
-			server.Logs = new(ServerLogConfig)
-		}
 
 			// save server
 			httpApp.Servers[fmt.Sprintf("static%d", i)] = server
 		}
+	} else {
+		server, err := buildHTTPServer(0, 0, listen, statusCode, hdr, body, accessLog)
+		if err != nil {
+			return caddy.ExitCodeFailedStartup, err
+		}
+
+		// save server
+		httpApp.Servers[fmt.Sprintf("static%d", 0)] = server
+	}
 
 	// finish building the config
 	var false bool