internal/lsp: refactor the command line handling

This switched the golsp binary to support a sub-command model so it can grow
some guru like command line query capabilites

Change-Id: I1a7a49bb17701e62004bba636d6bee9de2481ffd
Reviewed-on: https://go-review.googlesource.com/c/154559
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

cmd/golsp/main.go

@@ -10,148 +10,12 @@ package main // import "golang.org/x/tools/cmd/golsp"
 
 import (
 	"context"
-	"encoding/json"
-	"flag"
-	"fmt"
-	"io"
-	"log"
 	"os"
-	"path/filepath"
-	"runtime"
-	"runtime/pprof"
-	"runtime/trace"
-	"strings"
-	"time"
 
-	"golang.org/x/tools/internal/jsonrpc2"
+	"golang.org/x/tools/internal/lsp/cmd"
-	"golang.org/x/tools/internal/lsp"
+	"golang.org/x/tools/internal/tool"
-)
-
-var (
-	cpuprofile = flag.String("cpuprofile", "", "write CPU profile to this file")
-	memprofile = flag.String("memprofile", "", "write memory profile to this file")
-	traceFlag  = flag.String("trace", "", "write trace log to this file")
-	logfile    = flag.String("logfile", "", "filename to log to. if value is \"auto\", then logging to a default output file is enabled")
-
-	// Flags for compatitibility with VSCode.
-	mode = flag.String("mode", "", "no effect")
 )
 
 func main() {
-	flag.Usage = func() {
+	tool.Main(context.Background(), &cmd.Application{}, os.Args[1:])
-		fmt.Fprintf(os.Stderr, "usage: golsp [flags]\n")
-		flag.PrintDefaults()
-	}
-	flag.Parse()
-	if flag.NArg() > 0 {
-		flag.Usage()
-		os.Exit(2)
-	}
-
-	if *cpuprofile != "" {
-		f, err := os.Create(*cpuprofile)
-		if err != nil {
-			log.Fatal(err)
-		}
-		if err := pprof.StartCPUProfile(f); err != nil {
-			log.Fatal(err)
-		}
-		// NB: profile won't be written in case of error.
-		defer pprof.StopCPUProfile()
-	}
-
-	if *traceFlag != "" {
-		f, err := os.Create(*traceFlag)
-		if err != nil {
-			log.Fatal(err)
-		}
-		if err := trace.Start(f); err != nil {
-			log.Fatal(err)
-		}
-		// NB: trace log won't be written in case of error.
-		defer func() {
-			trace.Stop()
-			log.Printf("To view the trace, run:\n$ go tool trace view %s", *traceFlag)
-		}()
-	}
-
-	if *memprofile != "" {
-		f, err := os.Create(*memprofile)
-		if err != nil {
-			log.Fatal(err)
-		}
-		// NB: memprofile won't be written in case of error.
-		defer func() {
-			runtime.GC() // get up-to-date statistics
-			if err := pprof.WriteHeapProfile(f); err != nil {
-				log.Fatalf("Writing memory profile: %v", err)
-			}
-			f.Close()
-		}()
-	}
-
-	out := os.Stderr
-	if *logfile != "" {
-		filename := *logfile
-		if filename == "auto" {
-			filename = filepath.Join(os.TempDir(), fmt.Sprintf("golsp-%d.log", os.Getpid()))
-		}
-		f, err := os.Create(filename)
-		if err != nil {
-			log.Fatalf("Unable to create log file: %v", err)
-		}
-		defer f.Close()
-		log.SetOutput(io.MultiWriter(os.Stderr, f))
-		out = f
-	}
-	if err := lsp.RunServer(
-		context.Background(),
-		jsonrpc2.NewHeaderStream(os.Stdin, os.Stdout),
-		func(direction jsonrpc2.Direction, id *jsonrpc2.ID, elapsed time.Duration, method string, payload *json.RawMessage, err *jsonrpc2.Error) {
-
-			const eol = "\r\n\r\n\r\n"
-			if err != nil {
-				fmt.Fprintf(out, "[Error - %v] %s %s%s %v%s", time.Now().Format("3:04:05 PM"),
-					direction, method, id, err, eol)
-				return
-			}
-			outx := new(strings.Builder)
-			fmt.Fprintf(outx, "[Trace - %v] ", time.Now().Format("3:04:05 PM"))
-			switch direction {
-			case jsonrpc2.Send:
-				fmt.Fprint(outx, "Received ")
-			case jsonrpc2.Receive:
-				fmt.Fprint(outx, "Sending ")
-			}
-			switch {
-			case id == nil:
-				fmt.Fprint(outx, "notification ")
-			case elapsed >= 0:
-				fmt.Fprint(outx, "response ")
-			default:
-				fmt.Fprint(outx, "request ")
-			}
-			fmt.Fprintf(outx, "'%s", method)
-			switch {
-			case id == nil:
-				// do nothing
-			case id.Name != "":
-				fmt.Fprintf(outx, " - (%s)", id.Name)
-			default:
-				fmt.Fprintf(outx, " - (%d)", id.Number)
-			}
-			fmt.Fprint(outx, "'")
-			if elapsed >= 0 {
-				fmt.Fprintf(outx, " in %vms", elapsed.Nanoseconds()/1000)
-			}
-			params := string(*payload)
-			if params == "null" {
-				params = "{}"
-			}
-			fmt.Fprintf(outx, ".\r\nParams: %s%s", params, eol)
-			fmt.Fprintf(out, "%s", outx.String())
-		},
-	); err != nil {
-		log.Fatal(err)
-	}
 }

internal/lsp/cmd/cmd.go

@@ -0,0 +1,81 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package cmd handles the golsp command line.
+// It contains a handler for each of the modes, along with all the flag handling
+// and the command line output format.
+package cmd
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"golang.org/x/tools/internal/tool"
+)
+
+// Application is the main application as passed to tool.Main
+// It handles the main command line parsing and dispatch to the sub commands.
+type Application struct {
+	// Embed the basic profiling flags supported by the tool package
+	tool.Profile
+
+	// we also include the server directly for now, so the flags work even without
+	// the verb. We should remove this when we stop allowing the server verb by
+	// default
+	Server server
+}
+
+// Name implements tool.Application returning the binary name.
+func (app *Application) Name() string { return "golsp" }
+
+// Usage implements tool.Application returning empty extra argument usage.
+func (app *Application) Usage() string { return "<mode> [mode-flags] [mode-args]" }
+
+// ShortHelp implements tool.Application returning the main binary help.
+func (app *Application) ShortHelp() string {
+	return "The Go Language Smartness Provider."
+}
+
+// DetailedHelp implements tool.Application returning the main binary help.
+// This includes the short help for all the sub commands.
+func (app *Application) DetailedHelp(f *flag.FlagSet) {
+	fmt.Fprint(f.Output(), `
+Available modes are:
+`)
+	for _, c := range app.modes() {
+		fmt.Fprintf(f.Output(), "  %s : %v\n", c.Name(), c.ShortHelp())
+	}
+	fmt.Fprint(f.Output(), `
+golsp flags are:
+`)
+	f.PrintDefaults()
+}
+
+// Run takes the args after top level flag processing, and invokes the correct
+// sub command as specified by the first argument.
+// If no arguments are passed it will invoke the server sub command, as a
+// temporary measure for compatability.
+func (app *Application) Run(ctx context.Context, args ...string) error {
+	if len(args) == 0 {
+		tool.Main(ctx, &app.Server, args)
+		return nil
+	}
+	mode, args := args[0], args[1:]
+	for _, m := range app.modes() {
+		if m.Name() == mode {
+			tool.Main(ctx, m, args)
+			return nil
+		}
+	}
+	return tool.CommandLineErrorf("Unknown mode %v", mode)
+}
+
+// modes returns the set of command modes supported by the golsp tool on the
+// command line.
+// The mode is specified by the first non flag argument.
+func (app *Application) modes() []tool.Application {
+	return []tool.Application{
+		&app.Server,
+	}
+}

internal/lsp/cmd/server.go

@@ -0,0 +1,110 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cmd
+
+import (
+	"context"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"golang.org/x/tools/internal/jsonrpc2"
+	"golang.org/x/tools/internal/lsp"
+	"golang.org/x/tools/internal/tool"
+)
+
+// server is a struct that exposes the configurable parts of the LSP server as
+// flags, in the right form for tool.Main to consume.
+type server struct {
+	Logfile string `flag:"logfile" help:"filename to log to. if value is \"auto\", then logging to a default output file is enabled"`
+	Mode    string `flag:"mode" help:"no effect"`
+}
+
+func (s *server) Name() string  { return "server" }
+func (s *server) Usage() string { return "" }
+func (s *server) ShortHelp() string {
+	return "run a server for Go code using the Language Server Protocol"
+}
+func (s *server) DetailedHelp(f *flag.FlagSet) {
+	fmt.Fprint(f.Output(), `
+The server communicates using JSONRPC2 on stdin and stdout, and is intended to be run directly as
+a child of an editor process.
+`)
+}
+
+// Run configures a server based on the flags, and then runs it.
+// It blocks until the server shuts down.
+func (s *server) Run(ctx context.Context, args ...string) error {
+	if len(args) > 0 {
+		return tool.CommandLineErrorf("server does not take arguments, got %v", args)
+	}
+	out := os.Stderr
+	if s.Logfile != "" {
+		filename := s.Logfile
+		if filename == "auto" {
+			filename = filepath.Join(os.TempDir(), fmt.Sprintf("golsp-%d.log", os.Getpid()))
+		}
+		f, err := os.Create(filename)
+		if err != nil {
+			return fmt.Errorf("Unable to create log file: %v", err)
+		}
+		defer f.Close()
+		log.SetOutput(io.MultiWriter(os.Stderr, f))
+		out = f
+	}
+	return lsp.RunServer(
+		ctx,
+		jsonrpc2.NewHeaderStream(os.Stdin, os.Stdout),
+		func(direction jsonrpc2.Direction, id *jsonrpc2.ID, elapsed time.Duration, method string, payload *json.RawMessage, err *jsonrpc2.Error) {
+			const eol = "\r\n\r\n\r\n"
+			if err != nil {
+				fmt.Fprintf(out, "[Error - %v] %s %s%s %v%s", time.Now().Format("3:04:05 PM"),
+					direction, method, id, err, eol)
+				return
+			}
+			outx := new(strings.Builder)
+			fmt.Fprintf(outx, "[Trace - %v] ", time.Now().Format("3:04:05 PM"))
+			switch direction {
+			case jsonrpc2.Send:
+				fmt.Fprint(outx, "Received ")
+			case jsonrpc2.Receive:
+				fmt.Fprint(outx, "Sending ")
+			}
+			switch {
+			case id == nil:
+				fmt.Fprint(outx, "notification ")
+			case elapsed >= 0:
+				fmt.Fprint(outx, "response ")
+			default:
+				fmt.Fprint(outx, "request ")
+			}
+			fmt.Fprintf(outx, "'%s", method)
+			switch {
+			case id == nil:
+				// do nothing
+			case id.Name != "":
+				fmt.Fprintf(outx, " - (%s)", id.Name)
+			default:
+				fmt.Fprintf(outx, " - (%d)", id.Number)
+			}
+			fmt.Fprint(outx, "'")
+			if elapsed >= 0 {
+				fmt.Fprintf(outx, " in %vms", elapsed.Nanoseconds()/1000)
+			}
+			params := string(*payload)
+			if params == "null" {
+				params = "{}"
+			}
+			fmt.Fprintf(outx, ".\r\nParams: %s%s", params, eol)
+			fmt.Fprintf(out, "%s", outx.String())
+		},
+	)
+}