cmds/commands: Update 'client-addr' to support Unix domain sockets (#3819)

* cmds/commands: Update 'client-addr' to support Unix domain sockets

This change updates the '--client-addr' flag to accept Unix domain sockets (UDS). Currently, the --listen flag supports UDS, but --client-addr does not. This modification ensures consistency across the APIs and improves support for vscode-go, which uses reverse mode (via client-addr) to connect to DAP.

Fixes #3814

* Undo formatter changes in dlv_test.go

* Update commands.go

Documentation/usage/dlv_dap.md

@@ -33,7 +33,7 @@ dlv dap [flags]
 ### Options
 
 ```
-      --client-addr string   host:port where the DAP client is waiting for the DAP server to dial in
+      --client-addr string   Address where the DAP client is waiting for the DAP server to dial in. Prefix with 'unix:' to use a unix domain socket.
   -h, --help                 help for dap
 ```
 

cmd/dlv/cmds/commands.go

@@ -244,7 +244,7 @@ will exit when the debug session ends.`,
 		Run:               dapCmd,
 		ValidArgsFunction: cobra.NoFileCompletions,
 	}
-	dapCommand.Flags().StringVar(&dapClientAddr, "client-addr", "", "host:port where the DAP client is waiting for the DAP server to dial in")
+	dapCommand.Flags().StringVar(&dapClientAddr, "client-addr", "", "Address where the DAP client is waiting for the DAP server to dial in. Prefix with 'unix:' to use a unix domain socket.")
 	must(dapCommand.RegisterFlagCompletionFunc("client-addr", cobra.NoFileCompletions))
 
 	// TODO(polina): support --tty when dlv dap allows to launch a program from command-line
@@ -463,7 +463,8 @@ Some backends can be configured using environment variables:
 * DELVE_DEBUGSERVER_PATH specifies the path of the debugserver executable for the lldb backend
 * DELVE_RR_RECORD_FLAGS specifies additional flags used when calling 'rr record'
 * DELVE_RR_REPLAY_FLAGS specifies additional flags used when calling 'rr replay'
-`})
+`,
+	})
 
 	rootCommand.AddCommand(&cobra.Command{
 		Use:   "log",
@@ -581,12 +582,7 @@ func dapCmd(cmd *cobra.Command, args []string) {
 			}
 			cfg.Listener = listener
 		} else { // with a predetermined client.
-			var err error
+			conn = netDial(dapClientAddr)
-			conn, err = net.Dial("tcp", dapClientAddr)
-			if err != nil {
-				fmt.Fprintf(os.Stderr, "Failed to connect to the DAP client: %v\n", err)
-				return 1
-			}
 		}
 
 		server := dap.NewServer(cfg)

cmd/dlv/dlv_test.go

@@ -922,6 +922,53 @@ func TestDAPCmdWithClient(t *testing.T) {
 	}
 }
 
+// TestDAPCmdWithUnixClient tests dlv dap --client-addr can be started with unix domain socket and shut down.
+func TestDAPCmdWithUnixClient(t *testing.T) {
+	tmpdir := os.TempDir()
+	if tmpdir == "" {
+		return
+	}
+
+	listenPath := filepath.Join(tmpdir, "dap_test")
+	listener, err := net.Listen("unix", listenPath)
+	if err != nil {
+		t.Fatalf("cannot setup listener required for testing: %v", err)
+	}
+	defer listener.Close()
+
+	dlvbin := getDlvBin(t)
+
+	cmd := exec.Command(dlvbin, "dap", "--log-output=dap", "--log", "--client-addr=unix:"+listener.Addr().String())
+	buf := &bytes.Buffer{}
+	cmd.Stdin = buf
+	cmd.Stdout = buf
+	assertNoError(cmd.Start(), t, "start dlv dap process with --client-addr flag")
+
+	// Wait for the connection.
+	conn, err := listener.Accept()
+	if err != nil {
+		cmd.Process.Kill() // release the socket file
+		t.Fatalf("Failed to get connection: %v", err)
+	}
+	t.Log("dlv dap process dialed in successfully")
+
+	client := daptest.NewClientFromConn(conn)
+	client.InitializeRequest()
+	client.ExpectInitializeResponse(t)
+
+	// Close the connection.
+	if err := conn.Close(); err != nil {
+		cmd.Process.Kill()
+		t.Fatalf("Failed to get connection: %v", err)
+	}
+
+	// Connection close should trigger dlv-reverse command's normal exit.
+	if err := cmd.Wait(); err != nil {
+		cmd.Process.Kill()
+		t.Fatalf("command failed: %v\n%s\n%v", err, buf.Bytes(), cmd.Process.Pid)
+	}
+}
+
 func TestTrace(t *testing.T) {
 	dlvbin := getDlvBin(t)