1// Copyright 2019 The Go Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style 3// license that can be found in the LICENSE file. 4 5package cmd 6 7import ( 8 "context" 9 "flag" 10 "fmt" 11 12 "golang.org/x/tools/internal/lsp/protocol" 13 "golang.org/x/tools/internal/span" 14 "golang.org/x/tools/internal/tool" 15) 16 17// signature implements the signature verb for gopls 18type signature struct { 19 app *Application 20} 21 22func (r *signature) Name() string { return "signature" } 23func (r *signature) Usage() string { return "<position>" } 24func (r *signature) ShortHelp() string { return "display selected identifier's signature" } 25func (r *signature) DetailedHelp(f *flag.FlagSet) { 26 fmt.Fprint(f.Output(), ` 27Example: 28 29 $ # 1-indexed location (:line:column or :#offset) of the target identifier 30 $ gopls signature helper/helper.go:8:6 31 $ gopls signature helper/helper.go:#53 32 33 gopls signature flags are: 34`) 35 f.PrintDefaults() 36} 37 38func (r *signature) Run(ctx context.Context, args ...string) error { 39 if len(args) != 1 { 40 return tool.CommandLineErrorf("signature expects 1 argument (position)") 41 } 42 43 conn, err := r.app.connect(ctx) 44 if err != nil { 45 return err 46 } 47 defer conn.terminate(ctx) 48 49 from := span.Parse(args[0]) 50 file := conn.AddFile(ctx, from.URI()) 51 if file.err != nil { 52 return file.err 53 } 54 55 loc, err := file.mapper.Location(from) 56 if err != nil { 57 return err 58 } 59 60 tdpp := protocol.TextDocumentPositionParams{ 61 TextDocument: protocol.TextDocumentIdentifier{ 62 URI: protocol.URIFromSpanURI(from.URI()), 63 }, 64 Position: loc.Range.Start, 65 } 66 p := protocol.SignatureHelpParams{ 67 TextDocumentPositionParams: tdpp, 68 } 69 70 s, err := conn.SignatureHelp(ctx, &p) 71 if err != nil { 72 return err 73 } 74 75 if s == nil || len(s.Signatures) == 0 { 76 return tool.CommandLineErrorf("%v: not a function", from) 77 } 78 79 // there is only ever one possible signature, 80 // see toProtocolSignatureHelp in lsp/signature_help.go 81 signature := s.Signatures[0] 82 fmt.Printf("%s\n", signature.Label) 83 if signature.Documentation != "" { 84 fmt.Printf("\n%s\n", signature.Documentation) 85 } 86 87 return nil 88} 89