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// 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/gopls/internal/lsp/protocol"
"golang.org/x/tools/gopls/internal/span"
"golang.org/x/tools/internal/tool"
)
// signature implements the signature verb for gopls
type signature struct {
app *Application
}
func (r *signature) Name() string { return "signature" }
func (r *signature) Parent() string { return r.app.Name() }
func (r *signature) Usage() string { return "<position>" }
func (r *signature) ShortHelp() string { return "display selected identifier's signature" }
func (r *signature) DetailedHelp(f *flag.FlagSet) {
fmt.Fprint(f.Output(), `
Example:
$ # 1-indexed location (:line:column or :#offset) of the target identifier
$ gopls signature helper/helper.go:8:6
$ gopls signature helper/helper.go:#53
`)
printFlagDefaults(f)
}
func (r *signature) Run(ctx context.Context, args ...string) error {
if len(args) != 1 {
return tool.CommandLineErrorf("signature expects 1 argument (position)")
}
conn, err := r.app.connect(ctx)
if err != nil {
return err
}
defer conn.terminate(ctx)
from := span.Parse(args[0])
file := conn.openFile(ctx, from.URI())
if file.err != nil {
return file.err
}
loc, err := file.mapper.Location(from)
if err != nil {
return err
}
tdpp := protocol.TextDocumentPositionParams{
TextDocument: protocol.TextDocumentIdentifier{
URI: protocol.URIFromSpanURI(from.URI()),
},
Position: loc.Range.Start,
}
p := protocol.SignatureHelpParams{
TextDocumentPositionParams: tdpp,
}
s, err := conn.SignatureHelp(ctx, &p)
if err != nil {
return err
}
if s == nil || len(s.Signatures) == 0 {
return tool.CommandLineErrorf("%v: not a function", from)
}
// there is only ever one possible signature,
// see toProtocolSignatureHelp in lsp/signature_help.go
signature := s.Signatures[0]
fmt.Printf("%s\n", signature.Label)
if signature.Documentation != "" {
fmt.Printf("\n%s\n", signature.Documentation)
}
return nil
}
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