golang.org/x/tools/gopls@v0.15.3/internal/server/signature_help.go (about)

     1  // Copyright 2018 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  
     5  package server
     6  
     7  import (
     8  	"context"
     9  
    10  	"golang.org/x/tools/gopls/internal/file"
    11  	"golang.org/x/tools/gopls/internal/golang"
    12  	"golang.org/x/tools/gopls/internal/protocol"
    13  	"golang.org/x/tools/internal/event"
    14  	"golang.org/x/tools/internal/event/tag"
    15  )
    16  
    17  func (s *server) SignatureHelp(ctx context.Context, params *protocol.SignatureHelpParams) (*protocol.SignatureHelp, error) {
    18  	ctx, done := event.Start(ctx, "lsp.Server.signatureHelp", tag.URI.Of(params.TextDocument.URI))
    19  	defer done()
    20  
    21  	fh, snapshot, release, err := s.fileOf(ctx, params.TextDocument.URI)
    22  	if err != nil {
    23  		return nil, err
    24  	}
    25  	defer release()
    26  
    27  	if snapshot.FileKind(fh) != file.Go {
    28  		return nil, nil // empty result
    29  	}
    30  
    31  	info, activeParameter, err := golang.SignatureHelp(ctx, snapshot, fh, params.Position)
    32  	if err != nil {
    33  		event.Error(ctx, "no signature help", err, tag.Position.Of(params.Position))
    34  		return nil, nil // sic? There could be many reasons for failure.
    35  	}
    36  	return &protocol.SignatureHelp{
    37  		Signatures:      []protocol.SignatureInformation{*info},
    38  		ActiveParameter: uint32(activeParameter),
    39  	}, nil
    40  }