cmd/acme-lsp: add -rpc.trace flag

This helps with debugging LSP servers that don't do tracing.

internal/lsp/acmelsp/client.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"log"
 	"net"
+	"os"
 	"path/filepath"
 	"sync"
 
@@ -99,6 +100,7 @@ type ClientConfig struct {
 	*config.Server
 	RootDirectory string                     // used to compute RootURI in initialization
 	HideDiag      bool                       // don't write diagnostics to DiagWriter
+	RPCTrace      bool                       // print LSP rpc trace to stderr
 	DiagWriter    DiagnosticsWriter          // notification handler writes diagnostics here
 	Workspaces    []protocol.WorkspaceFolder // initial workspace folders
 	Logger        *log.Logger
@@ -121,6 +123,9 @@ func NewClient(conn net.Conn, cfg *ClientConfig) (*Client, error) {
 func (c *Client) init(conn net.Conn, cfg *ClientConfig) error {
 	ctx := context.Background()
 	stream := jsonrpc2.NewHeaderStream(conn, conn)
+	if cfg.RPCTrace {
+		stream = protocol.LoggingStream(stream, os.Stderr)
+	}
 	ctx, rpc, server := protocol.NewClient(ctx, stream, &clientHandler{
 		cfg:        cfg,
 		hideDiag:   cfg.HideDiag,

internal/lsp/acmelsp/config/config.go

@@ -50,6 +50,9 @@ type File struct {
 	// Format file when Put is executed in a window.
 	FormatOnPut bool
 
+	// Print to stderr the full rpc trace in lsp inspector format
+	RPCTrace bool
+
 	// LSP code actions to run when Put is executed in a window.
 	CodeActionsOnPut []protocol.CodeActionKind
 
@@ -247,6 +250,7 @@ func (cfg *Config) ParseFlags(flags Flags, f *flag.FlagSet, arguments []string)
 		f.BoolVar(&cfg.Verbose, "debug", cfg.Verbose, "turn on debugging prints (deprecated: use -v)")
 		f.StringVar(&cfg.RootDirectory, "rootdir", cfg.RootDirectory, "root directory used for LSP initialization")
 		f.BoolVar(&cfg.HideDiagnostics, "hidediag", false, "hide diagnostics sent by LSP server")
+		f.BoolVar(&cfg.RPCTrace, "rpc.trace", false, "print the full rpc trace in lsp inspector format")
 		f.StringVar(&workspaces, "workspaces", "", "colon-separated list of initial workspace directories")
 		f.Var(&userServers, "server", `language server command for filename match (e.g. '\.go$:gopls')`)
 		f.Var(&dialServers, "dial", `language server address for filename match (e.g. '\.go$:localhost:4389')`)

internal/lsp/acmelsp/exec.go

@@ -217,6 +217,7 @@ func (ss *ServerSet) ClientConfig(info *ServerInfo) *ClientConfig {
 		Server:        info.Server,
 		RootDirectory: ss.cfg.RootDirectory,
 		HideDiag:      ss.cfg.HideDiagnostics,
+		RPCTrace:      ss.cfg.RPCTrace,
 		DiagWriter:    ss.diagWriter,
 		Workspaces:    ss.Workspaces(),
 		Logger:        info.Logger,