--- /dev/null
+// 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"
+ errors "golang.org/x/xerrors"
+)
+
+// 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()
+}
+
+// ErrInvalidRenamePosition is returned when prepareRename is run at a position that
+// is not a candidate for renaming.
+var ErrInvalidRenamePosition = errors.New("request is not valid at the given position")
+
+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 errors.Errorf("prepare_rename failed: %w", err)
+ }
+ if result == nil {
+ return ErrInvalidRenamePosition
+ }
+
+ l := protocol.Location{Range: *result}
+ s, err := file.mapper.Span(l)
+ if err != nil {
+ return err
+ }
+
+ fmt.Println(s)
+ return nil
+}