tools/gopls: add cmd support for prepare_rename

Updates golang/go#32875

internal/lsp/cmd/cmd.go

@@ -174,6 +174,7 @@ func (app *Application) featureCommands() []tool.Application {
 		&implementation{app: app},
 		&imports{app: app},
 		&links{app: app},
+		&prepareRename{app: app},
 		&query{app: app},
 		&references{app: app},
 		&rename{app: app},

internal/lsp/cmd/prepare_rename.go

@@ -0,0 +1,89 @@
+// Copyright 2019 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"
+	"flag"
+	"fmt"
+
+	"golang.org/x/tools/internal/lsp/protocol"
+	"golang.org/x/tools/internal/span"
+	"golang.org/x/tools/internal/tool"
+)
+
+// prepareRename implements the prepare_rename verb for gopls.
+type prepareRename struct {
+	app *Application
+}
+
+func (r *prepareRename) Name() string      { return "prepare_rename" }
+func (r *prepareRename) Usage() string     { return "<position>" }
+func (r *prepareRename) ShortHelp() string { return "test validity of a rename operation at location" }
+func (r *prepareRename) DetailedHelp(f *flag.FlagSet) {
+	fmt.Fprint(f.Output(), `
+Example:
+
+	$ # 1-indexed location (:line:column or :#offset) of the target identifier
+	$ gopls prepare_rename helper/helper.go:8:6
+	$ gopls prepare_rename helper/helper.go:#53
+
+	gopls prepare_rename flags are:
+`)
+	f.PrintDefaults()
+}
+
+func (r *prepareRename) Run(ctx context.Context, args ...string) error {
+	if len(args) != 1 {
+		return tool.CommandLineErrorf("prepare_rename expects 1 argument (file)")
+	}
+
+	conn, err := r.app.connect(ctx)
+	if err != nil {
+		return err
+	}
+	defer conn.terminate(ctx)
+
+	from := span.Parse(args[0])
+	file := conn.AddFile(ctx, from.URI())
+	if file.err != nil {
+		return file.err
+	}
+	loc, err := file.mapper.Location(from)
+	if err != nil {
+		return err
+	}
+	p := protocol.PrepareRenameParams{
+		TextDocumentPositionParams: protocol.TextDocumentPositionParams{
+			TextDocument: protocol.TextDocumentIdentifier{URI: loc.URI},
+			Position:     loc.Range.Start,
+		},
+	}
+	result, err := conn.PrepareRename(ctx, &p)
+	if err != nil {
+		return fmt.Errorf("prepare_rename failed: %v", err)
+	}
+	if result == nil {
+		return fmt.Errorf("request is not valid at the given position")
+	}
+
+	resRange, ok := result.(protocol.Range)
+	if !ok {
+		return fmt.Errorf("prepare_rename failed to convert result to range, got: %T", result)
+	}
+
+	l := protocol.Location{Range: resRange}
+	s, err := file.mapper.Span(l)
+	if err != nil {
+		return err
+	}
+
+	if s.IsPoint() {
+		return fmt.Errorf("request is not valid at the given position")
+	}
+
+	fmt.Println(s)
+	return nil
+}

internal/lsp/cmd/test/cmdtest.go

@@ -95,10 +95,6 @@ func (r *runner) RankCompletion(t *testing.T, src span.Span, test tests.Completi
 	//TODO: add command line completions tests when it works
 }
 
-func (r *runner) PrepareRename(t *testing.T, src span.Span, want *source.PrepareItem) {
-	//TODO: add command line prepare rename tests when it works
-}
-
 func (r *runner) RunGoplsCmd(t testing.TB, args ...string) (string, string) {
 	rStdout, wStdout, err := os.Pipe()
 	if err != nil {

internal/lsp/cmd/test/prepare_rename.go

@@ -0,0 +1,46 @@
+// Copyright 2019 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 cmdtest
+
+import (
+	"fmt"
+	"testing"
+
+	"golang.org/x/tools/internal/lsp/protocol"
+	"golang.org/x/tools/internal/lsp/source"
+	"golang.org/x/tools/internal/span"
+)
+
+func (r *runner) PrepareRename(t *testing.T, src span.Span, want *source.PrepareItem) {
+	m, err := r.data.Mapper(src.URI())
+	if err != nil {
+		t.Errorf("prepare_rename failed: %v", err)
+	}
+
+	var (
+		target         = fmt.Sprintf("%v", src)
+		args           = []string{"prepare_rename", target}
+		stdOut, stdErr = r.NormalizeGoplsCmd(t, args...)
+		expect         string
+	)
+
+	if want.Text == "" {
+		expect = "request is not valid at the given position"
+		if stdErr != expect {
+			t.Errorf("prepare_rename failed for %s,\nexpected:\n`%v`\ngot:\n`%v`", target, expect, stdErr)
+		}
+		return
+	}
+
+	ws, err := m.Span(protocol.Location{Range: want.Range})
+	if err != nil {
+		t.Errorf("prepare_rename failed: %v", err)
+	}
+
+	expect = r.Normalize(fmt.Sprintln(ws))
+	if expect != stdOut {
+		t.Errorf("prepare_rename failed for %s expected:\n`%s`\ngot:\n`%s`\n", target, expect, stdOut)
+	}
+}