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// Copyright 2022 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 golang
import (
"context"
"errors"
"fmt"
"go/ast"
"go/doc/comment"
"go/token"
"go/types"
"strings"
"golang.org/x/tools/gopls/internal/cache"
"golang.org/x/tools/gopls/internal/cache/parsego"
"golang.org/x/tools/gopls/internal/protocol"
"golang.org/x/tools/gopls/internal/settings"
"golang.org/x/tools/gopls/internal/util/safetoken"
)
var errNoCommentReference = errors.New("no comment reference found")
// CommentToMarkdown converts comment text to formatted markdown.
// The comment was prepared by DocReader,
// so it is known not to have leading, trailing blank lines
// nor to have trailing spaces at the end of lines.
// The comment markers have already been removed.
func CommentToMarkdown(text string, options *settings.Options) string {
var p comment.Parser
doc := p.Parse(text)
var pr comment.Printer
// The default produces {#Hdr-...} tags for headings.
// vscode displays thems, which is undesirable.
// The godoc for comment.Printer says the tags
// avoid a security problem.
pr.HeadingID = func(*comment.Heading) string { return "" }
pr.DocLinkURL = func(link *comment.DocLink) string {
msg := fmt.Sprintf("https://%s/%s", options.LinkTarget, link.ImportPath)
if link.Name != "" {
msg += "#"
if link.Recv != "" {
msg += link.Recv + "."
}
msg += link.Name
}
return msg
}
easy := pr.Markdown(doc)
return string(easy)
}
// docLinkDefinition finds the definition of the doc link in comments at pos.
// If there is no reference at pos, returns errNoCommentReference.
func docLinkDefinition(ctx context.Context, snapshot *cache.Snapshot, pkg *cache.Package, pgf *parsego.File, pos token.Pos) ([]protocol.Location, error) {
obj, _, err := parseDocLink(pkg, pgf, pos)
if err != nil {
return nil, err
}
loc, err := mapPosition(ctx, pkg.FileSet(), snapshot, obj.Pos(), adjustedObjEnd(obj))
if err != nil {
return nil, err
}
return []protocol.Location{loc}, nil
}
// parseDocLink parses a doc link in a comment such as [fmt.Println]
// and returns the symbol at pos, along with the link's start position.
func parseDocLink(pkg *cache.Package, pgf *parsego.File, pos token.Pos) (types.Object, protocol.Range, error) {
var comment *ast.Comment
for _, cg := range pgf.File.Comments {
for _, c := range cg.List {
if c.Pos() <= pos && pos <= c.End() {
comment = c
break
}
}
if comment != nil {
break
}
}
if comment == nil {
return nil, protocol.Range{}, errNoCommentReference
}
// The canonical parsing algorithm is defined by go/doc/comment, but
// unfortunately its API provides no way to reliably reconstruct the
// position of each doc link from the parsed result.
line := safetoken.Line(pgf.Tok, pos)
var start, end token.Pos
if pgf.Tok.LineStart(line) > comment.Pos() {
start = pgf.Tok.LineStart(line)
} else {
start = comment.Pos()
}
if line < pgf.Tok.LineCount() && pgf.Tok.LineStart(line+1) < comment.End() {
end = pgf.Tok.LineStart(line + 1)
} else {
end = comment.End()
}
offsetStart, offsetEnd, err := safetoken.Offsets(pgf.Tok, start, end)
if err != nil {
return nil, protocol.Range{}, err
}
text := string(pgf.Src[offsetStart:offsetEnd])
lineOffset := int(pos - start)
for _, idx := range docLinkRegex.FindAllStringSubmatchIndex(text, -1) {
// The [idx[2], idx[3]) identifies the first submatch,
// which is the reference name in the doc link.
// e.g. The "[fmt.Println]" reference name is "fmt.Println".
if !(idx[2] <= lineOffset && lineOffset < idx[3]) {
continue
}
p := lineOffset - idx[2]
name := text[idx[2]:idx[3]]
i := strings.LastIndexByte(name, '.')
for i != -1 {
if p > i {
break
}
name = name[:i]
i = strings.LastIndexByte(name, '.')
}
obj := lookupObjectByName(pkg, pgf, name)
if obj == nil {
return nil, protocol.Range{}, errNoCommentReference
}
namePos := start + token.Pos(idx[2]+i+1)
rng, err := pgf.PosRange(namePos, namePos+token.Pos(len(obj.Name())))
if err != nil {
return nil, protocol.Range{}, err
}
return obj, rng, nil
}
return nil, protocol.Range{}, errNoCommentReference
}
func lookupObjectByName(pkg *cache.Package, pgf *parsego.File, name string) types.Object {
scope := pkg.Types().Scope()
fileScope := pkg.TypesInfo().Scopes[pgf.File]
pkgName, suffix, _ := strings.Cut(name, ".")
obj, ok := fileScope.Lookup(pkgName).(*types.PkgName)
if ok {
scope = obj.Imported().Scope()
if suffix == "" {
return obj
}
name = suffix
}
recv, method, ok := strings.Cut(name, ".")
if ok {
obj, ok := scope.Lookup(recv).(*types.TypeName)
if !ok {
return nil
}
t, ok := obj.Type().(*types.Named)
if !ok {
return nil
}
for i := 0; i < t.NumMethods(); i++ {
m := t.Method(i)
if m.Name() == method {
return m
}
}
return nil
}
return scope.Lookup(name)
}
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