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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 source
import (
"context"
"encoding/json"
"fmt"
"go/ast"
"go/constant"
"go/doc"
"go/format"
"go/token"
"go/types"
"strconv"
"strings"
"time"
"unicode/utf8"
"golang.org/x/text/unicode/runenames"
"golang.org/x/tools/internal/event"
"golang.org/x/tools/internal/lsp/protocol"
"golang.org/x/tools/internal/typeparams"
errors "golang.org/x/xerrors"
)
type HoverInformation struct {
// Signature is the symbol's signature.
Signature string `json:"signature"`
// SingleLine is a single line describing the symbol.
// This is recommended only for use in clients that show a single line for hover.
SingleLine string `json:"singleLine"`
// Synopsis is a single sentence synopsis of the symbol's documentation.
Synopsis string `json:"synopsis"`
// FullDocumentation is the symbol's full documentation.
FullDocumentation string `json:"fullDocumentation"`
// LinkPath is the pkg.go.dev link for the given symbol.
// For example, the "go/ast" part of "pkg.go.dev/go/ast#Node".
LinkPath string `json:"linkPath"`
// LinkAnchor is the pkg.go.dev link anchor for the given symbol.
// For example, the "Node" part of "pkg.go.dev/go/ast#Node".
LinkAnchor string `json:"linkAnchor"`
// importPath is the import path for the package containing the given
// symbol.
importPath string
// symbolName is the types.Object.Name for the given symbol.
symbolName string
source interface{}
comment *ast.CommentGroup
// typeName contains the identifier name when the identifier is a type declaration.
// If it is not empty, the hover will have the prefix "type <typeName> ".
typeName string
// isTypeAlias indicates whether the identifier is a type alias declaration.
// If it is true, the hover will have the prefix "type <typeName> = ".
isTypeAlias bool
}
func Hover(ctx context.Context, snapshot Snapshot, fh FileHandle, position protocol.Position) (*protocol.Hover, error) {
ident, err := Identifier(ctx, snapshot, fh, position)
if err != nil {
if hover, innerErr := hoverRune(ctx, snapshot, fh, position); innerErr == nil {
return hover, nil
}
return nil, nil
}
h, err := HoverIdentifier(ctx, ident)
if err != nil {
return nil, err
}
rng, err := ident.Range()
if err != nil {
return nil, err
}
// See golang/go#36998: don't link to modules matching GOPRIVATE.
if snapshot.View().IsGoPrivatePath(h.importPath) {
h.LinkPath = ""
}
hover, err := FormatHover(h, snapshot.View().Options())
if err != nil {
return nil, err
}
return &protocol.Hover{
Contents: protocol.MarkupContent{
Kind: snapshot.View().Options().PreferredContentFormat,
Value: hover,
},
Range: rng,
}, nil
}
func hoverRune(ctx context.Context, snapshot Snapshot, fh FileHandle, position protocol.Position) (*protocol.Hover, error) {
ctx, done := event.Start(ctx, "source.hoverRune")
defer done()
r, mrng, err := findRune(ctx, snapshot, fh, position)
if err != nil {
return nil, err
}
rng, err := mrng.Range()
if err != nil {
return nil, err
}
var desc string
runeName := runenames.Name(r)
if len(runeName) > 0 && runeName[0] == '<' {
// Check if the rune looks like an HTML tag. If so, trim the surrounding <>
// characters to work around https://github.com/microsoft/vscode/issues/124042.
runeName = strings.TrimRight(runeName[1:], ">")
}
if strconv.IsPrint(r) {
desc = fmt.Sprintf("'%s', U+%04X, %s", string(r), uint32(r), runeName)
} else {
desc = fmt.Sprintf("U+%04X, %s", uint32(r), runeName)
}
return &protocol.Hover{
Contents: protocol.MarkupContent{
Kind: snapshot.View().Options().PreferredContentFormat,
Value: desc,
},
Range: rng,
}, nil
}
// ErrNoRuneFound is the error returned when no rune is found at a particular position.
var ErrNoRuneFound = errors.New("no rune found")
// findRune returns rune information for a position in a file.
func findRune(ctx context.Context, snapshot Snapshot, fh FileHandle, position protocol.Position) (rune, MappedRange, error) {
pkg, pgf, err := GetParsedFile(ctx, snapshot, fh, NarrowestPackage)
if err != nil {
return 0, MappedRange{}, err
}
spn, err := pgf.Mapper.PointSpan(position)
if err != nil {
return 0, MappedRange{}, err
}
rng, err := spn.Range(pgf.Mapper.Converter)
if err != nil {
return 0, MappedRange{}, err
}
pos := rng.Start
// Find the basic literal enclosing the given position, if there is one.
var lit *ast.BasicLit
var found bool
ast.Inspect(pgf.File, func(n ast.Node) bool {
if found {
return false
}
if n, ok := n.(*ast.BasicLit); ok && pos >= n.Pos() && pos <= n.End() {
lit = n
found = true
}
return !found
})
if !found {
return 0, MappedRange{}, ErrNoRuneFound
}
var r rune
var start, end token.Pos
switch lit.Kind {
case token.CHAR:
s, err := strconv.Unquote(lit.Value)
if err != nil {
// If the conversion fails, it's because of an invalid syntax, therefore
// there is no rune to be found.
return 0, MappedRange{}, ErrNoRuneFound
}
r, _ = utf8.DecodeRuneInString(s)
if r == utf8.RuneError {
return 0, MappedRange{}, fmt.Errorf("rune error")
}
start, end = lit.Pos(), lit.End()
case token.INT:
// It's an integer, scan only if it is a hex litteral whose bitsize in
// ranging from 8 to 32.
if !(strings.HasPrefix(lit.Value, "0x") && len(lit.Value[2:]) >= 2 && len(lit.Value[2:]) <= 8) {
return 0, MappedRange{}, ErrNoRuneFound
}
v, err := strconv.ParseUint(lit.Value[2:], 16, 32)
if err != nil {
return 0, MappedRange{}, err
}
r = rune(v)
if r == utf8.RuneError {
return 0, MappedRange{}, fmt.Errorf("rune error")
}
start, end = lit.Pos(), lit.End()
case token.STRING:
// It's a string, scan only if it contains a unicode escape sequence under or before the
// current cursor position.
var found bool
litOffset, err := Offset(pgf.Tok, lit.Pos())
if err != nil {
return 0, MappedRange{}, err
}
offset, err := Offset(pgf.Tok, pos)
if err != nil {
return 0, MappedRange{}, err
}
for i := offset - litOffset; i > 0; i-- {
// Start at the cursor position and search backward for the beginning of a rune escape sequence.
rr, _ := utf8.DecodeRuneInString(lit.Value[i:])
if rr == utf8.RuneError {
return 0, MappedRange{}, fmt.Errorf("rune error")
}
if rr == '\\' {
// Got the beginning, decode it.
var tail string
r, _, tail, err = strconv.UnquoteChar(lit.Value[i:], '"')
if err != nil {
// If the conversion fails, it's because of an invalid syntax, therefore is no rune to be found.
return 0, MappedRange{}, ErrNoRuneFound
}
// Only the rune escape sequence part of the string has to be highlighted, recompute the range.
runeLen := len(lit.Value) - (int(i) + len(tail))
start = token.Pos(int(lit.Pos()) + int(i))
end = token.Pos(int(start) + runeLen)
found = true
break
}
}
if !found {
// No escape sequence found
return 0, MappedRange{}, ErrNoRuneFound
}
default:
return 0, MappedRange{}, ErrNoRuneFound
}
mappedRange, err := posToMappedRange(snapshot, pkg, start, end)
if err != nil {
return 0, MappedRange{}, err
}
return r, mappedRange, nil
}
func HoverIdentifier(ctx context.Context, i *IdentifierInfo) (*HoverInformation, error) {
ctx, done := event.Start(ctx, "source.Hover")
defer done()
fset := i.Snapshot.FileSet()
h, err := HoverInfo(ctx, i.Snapshot, i.pkg, i.Declaration.obj, i.Declaration.node, i.Declaration.fullDecl)
if err != nil {
return nil, err
}
// Determine the symbol's signature.
switch x := h.source.(type) {
case ast.Node:
var b strings.Builder
if err := format.Node(&b, fset, x); err != nil {
return nil, err
}
h.Signature = b.String()
if h.typeName != "" {
prefix := "type " + h.typeName + " "
if h.isTypeAlias {
prefix += "= "
}
h.Signature = prefix + h.Signature
}
// Check if the variable is an integer whose value we can present in a more
// user-friendly way, i.e. `var hex = 0xe34e` becomes `var hex = 58190`
if spec, ok := x.(*ast.ValueSpec); ok && len(spec.Values) > 0 {
if lit, ok := spec.Values[0].(*ast.BasicLit); ok && len(spec.Names) > 0 {
val := constant.MakeFromLiteral(types.ExprString(lit), lit.Kind, 0)
h.Signature = fmt.Sprintf("var %s = %s", spec.Names[0], val)
}
}
case types.Object:
// If the variable is implicitly declared in a type switch, we need to
// manually generate its object string.
if typ := i.Declaration.typeSwitchImplicit; typ != nil {
if v, ok := x.(*types.Var); ok {
h.Signature = fmt.Sprintf("var %s %s", v.Name(), types.TypeString(typ, i.qf))
break
}
}
h.Signature = objectString(x, i.qf, i.Inferred)
}
if obj := i.Declaration.obj; obj != nil {
h.SingleLine = objectString(obj, i.qf, nil)
}
obj := i.Declaration.obj
if obj == nil {
return h, nil
}
switch obj := obj.(type) {
case *types.PkgName:
h.importPath = obj.Imported().Path()
h.LinkPath = h.importPath
h.symbolName = obj.Name()
if mod, version, ok := moduleAtVersion(h.LinkPath, i); ok {
h.LinkPath = strings.Replace(h.LinkPath, mod, mod+"@"+version, 1)
}
return h, nil
case *types.Builtin:
h.importPath = "builtin"
h.LinkPath = h.importPath
h.LinkAnchor = obj.Name()
h.symbolName = h.LinkAnchor
return h, nil
}
// Check if the identifier is test-only (and is therefore not part of a
// package's API). This is true if the request originated in a test package,
// and if the declaration is also found in the same test package.
if i.pkg != nil && obj.Pkg() != nil && i.pkg.ForTest() != "" {
if _, err := i.pkg.File(i.Declaration.MappedRange[0].URI()); err == nil {
return h, nil
}
}
// Don't return links for other unexported types.
if !obj.Exported() {
return h, nil
}
var rTypeName string
switch obj := obj.(type) {
case *types.Var:
// If the object is a field, and we have an associated selector
// composite literal, or struct, we can determine the link.
if obj.IsField() {
if named, ok := i.enclosing.(*types.Named); ok {
rTypeName = named.Obj().Name()
}
}
case *types.Func:
typ, ok := obj.Type().(*types.Signature)
if !ok {
return h, nil
}
if r := typ.Recv(); r != nil {
switch rtyp := Deref(r.Type()).(type) {
case *types.Struct:
rTypeName = r.Name()
case *types.Named:
// If we have an unexported type, see if the enclosing type is
// exported (we may have an interface or struct we can link
// to). If not, don't show any link.
if !rtyp.Obj().Exported() {
if named, ok := i.enclosing.(*types.Named); ok && named.Obj().Exported() {
rTypeName = named.Obj().Name()
} else {
return h, nil
}
} else {
rTypeName = rtyp.Obj().Name()
}
}
}
}
if obj.Pkg() == nil {
event.Log(ctx, fmt.Sprintf("nil package for %s", obj))
return h, nil
}
h.importPath = obj.Pkg().Path()
h.LinkPath = h.importPath
if mod, version, ok := moduleAtVersion(h.LinkPath, i); ok {
h.LinkPath = strings.Replace(h.LinkPath, mod, mod+"@"+version, 1)
}
if rTypeName != "" {
h.LinkAnchor = fmt.Sprintf("%s.%s", rTypeName, obj.Name())
h.symbolName = fmt.Sprintf("(%s.%s).%s", obj.Pkg().Name(), rTypeName, obj.Name())
return h, nil
}
// For most cases, the link is "package/path#symbol".
h.LinkAnchor = obj.Name()
h.symbolName = fmt.Sprintf("%s.%s", obj.Pkg().Name(), obj.Name())
return h, nil
}
func moduleAtVersion(path string, i *IdentifierInfo) (string, string, bool) {
if strings.ToLower(i.Snapshot.View().Options().LinkTarget) != "pkg.go.dev" {
return "", "", false
}
impPkg, err := i.pkg.GetImport(path)
if err != nil {
return "", "", false
}
if impPkg.Version() == nil {
return "", "", false
}
version, modpath := impPkg.Version().Version, impPkg.Version().Path
if modpath == "" || version == "" {
return "", "", false
}
return modpath, version, true
}
// objectString is a wrapper around the types.ObjectString function.
// It handles adding more information to the object string.
func objectString(obj types.Object, qf types.Qualifier, inferred *types.Signature) string {
// If the signature type was inferred, prefer the preferred signature with a
// comment showing the generic signature.
if sig, _ := obj.Type().(*types.Signature); sig != nil && typeparams.ForSignature(sig).Len() > 0 && inferred != nil {
obj2 := types.NewFunc(obj.Pos(), obj.Pkg(), obj.Name(), inferred)
str := types.ObjectString(obj2, qf)
// Try to avoid overly long lines.
if len(str) > 60 {
str += "\n"
} else {
str += " "
}
str += "// " + types.TypeString(sig, qf)
return str
}
str := types.ObjectString(obj, qf)
switch obj := obj.(type) {
case *types.Const:
str = fmt.Sprintf("%s = %s", str, obj.Val())
// Try to add a formatted duration as an inline comment
typ, ok := obj.Type().(*types.Named)
if !ok {
break
}
pkg := typ.Obj().Pkg()
if pkg.Path() == "time" && typ.Obj().Name() == "Duration" {
if d, ok := constant.Int64Val(obj.Val()); ok {
str += " // " + time.Duration(d).String()
}
}
}
return str
}
// HoverInfo returns a HoverInformation struct for an ast node and its type
// object. node should be the actual node used in type checking, while fullNode
// could be a separate node with more complete syntactic information.
func HoverInfo(ctx context.Context, s Snapshot, pkg Package, obj types.Object, pkgNode ast.Node, fullDecl ast.Decl) (*HoverInformation, error) {
var info *HoverInformation
// This is problematic for a number of reasons. We really need to have a more
// general mechanism to validate the coherency of AST with type information,
// but absent that we must do our best to ensure that we don't use fullNode
// when we actually need the node that was type checked.
//
// pkgNode may be nil, if it was eliminated from the type-checked syntax. In
// that case, use fullDecl if available.
node := pkgNode
if node == nil && fullDecl != nil {
node = fullDecl
}
switch node := node.(type) {
case *ast.Ident:
// The package declaration.
for _, f := range pkg.GetSyntax() {
if f.Name == pkgNode {
info = &HoverInformation{comment: f.Doc}
}
}
case *ast.ImportSpec:
// Try to find the package documentation for an imported package.
if pkgName, ok := obj.(*types.PkgName); ok {
imp, err := pkg.GetImport(pkgName.Imported().Path())
if err != nil {
return nil, err
}
// Assume that only one file will contain package documentation,
// so pick the first file that has a doc comment.
for _, file := range imp.GetSyntax() {
if file.Doc != nil {
info = &HoverInformation{source: obj, comment: file.Doc}
break
}
}
}
info = &HoverInformation{source: node}
case *ast.GenDecl:
switch obj := obj.(type) {
case *types.TypeName, *types.Var, *types.Const, *types.Func:
// Always use the full declaration here if we have it, because the
// dependent code doesn't rely on pointer identity. This is fragile.
if d, _ := fullDecl.(*ast.GenDecl); d != nil {
node = d
}
// obj may not have been produced by type checking the AST containing
// node, so we need to be careful about using token.Pos.
tok := s.FileSet().File(obj.Pos())
offset, err := Offset(tok, obj.Pos())
if err != nil {
return nil, err
}
tok2 := s.FileSet().File(node.Pos())
var spec ast.Spec
for _, s := range node.Specs {
// Avoid panics by guarding the calls to token.Offset (golang/go#48249).
start, err := Offset(tok2, s.Pos())
if err != nil {
return nil, err
}
end, err := Offset(tok2, s.End())
if err != nil {
return nil, err
}
if start <= offset && offset <= end {
spec = s
break
}
}
info, err = formatGenDecl(node, spec, obj, obj.Type())
if err != nil {
return nil, err
}
}
case *ast.TypeSpec:
if obj.Parent() == types.Universe {
if obj.Name() == "error" {
info = &HoverInformation{source: node}
} else {
info = &HoverInformation{source: node.Name} // comments not needed for builtins
}
}
case *ast.FuncDecl:
switch obj.(type) {
case *types.Func:
info = &HoverInformation{source: obj, comment: node.Doc}
case *types.Builtin:
info = &HoverInformation{source: node.Type, comment: node.Doc}
case *types.Var:
// Object is a function param or the field of an anonymous struct
// declared with ':='. Skip the first one because only fields
// can have docs.
if isFunctionParam(obj, node) {
break
}
field, err := s.PosToField(ctx, pkg, obj.Pos())
if err != nil {
return nil, err
}
if field != nil {
comment := field.Doc
if comment.Text() == "" {
comment = field.Comment
}
info = &HoverInformation{source: obj, comment: comment}
}
}
}
if info == nil {
info = &HoverInformation{source: obj}
}
if info.comment != nil {
info.FullDocumentation = info.comment.Text()
info.Synopsis = doc.Synopsis(info.FullDocumentation)
}
return info, nil
}
// isFunctionParam returns true if the passed object is either an incoming
// or an outgoing function param
func isFunctionParam(obj types.Object, node *ast.FuncDecl) bool {
for _, f := range node.Type.Params.List {
if f.Pos() == obj.Pos() {
return true
}
}
if node.Type.Results != nil {
for _, f := range node.Type.Results.List {
if f.Pos() == obj.Pos() {
return true
}
}
}
return false
}
func formatGenDecl(node *ast.GenDecl, spec ast.Spec, obj types.Object, typ types.Type) (*HoverInformation, error) {
if _, ok := typ.(*types.Named); ok {
switch typ.Underlying().(type) {
case *types.Interface, *types.Struct:
return formatGenDecl(node, spec, obj, typ.Underlying())
}
}
if spec == nil {
return nil, errors.Errorf("no spec for node %v at position %v", node, obj.Pos())
}
// If we have a field or method.
switch obj.(type) {
case *types.Var, *types.Const, *types.Func:
return formatVar(spec, obj, node), nil
}
// Handle types.
switch spec := spec.(type) {
case *ast.TypeSpec:
return formatTypeSpec(spec, node), nil
case *ast.ValueSpec:
return &HoverInformation{source: spec, comment: spec.Doc}, nil
case *ast.ImportSpec:
return &HoverInformation{source: spec, comment: spec.Doc}, nil
}
return nil, errors.Errorf("unable to format spec %v (%T)", spec, spec)
}
func formatTypeSpec(spec *ast.TypeSpec, decl *ast.GenDecl) *HoverInformation {
comment := spec.Doc
if comment == nil && decl != nil {
comment = decl.Doc
}
if comment == nil {
comment = spec.Comment
}
return &HoverInformation{
source: spec.Type,
comment: comment,
typeName: spec.Name.Name,
isTypeAlias: spec.Assign.IsValid(),
}
}
func formatVar(node ast.Spec, obj types.Object, decl *ast.GenDecl) *HoverInformation {
var fieldList *ast.FieldList
switch spec := node.(type) {
case *ast.TypeSpec:
switch t := spec.Type.(type) {
case *ast.StructType:
fieldList = t.Fields
case *ast.InterfaceType:
fieldList = t.Methods
}
case *ast.ValueSpec:
// Try to extract the field list of an anonymous struct
if fieldList = extractFieldList(spec.Type); fieldList != nil {
break
}
comment := spec.Doc
if comment == nil {
comment = decl.Doc
}
if comment == nil {
comment = spec.Comment
}
// We need the AST nodes for variable declarations of basic literals with
// associated values so that we can augment their hover with more information.
if _, ok := obj.(*types.Var); ok && spec.Type == nil && len(spec.Values) > 0 {
if _, ok := spec.Values[0].(*ast.BasicLit); ok {
return &HoverInformation{source: spec, comment: comment}
}
}
return &HoverInformation{source: obj, comment: comment}
}
if fieldList != nil {
comment := findFieldComment(obj.Pos(), fieldList)
return &HoverInformation{source: obj, comment: comment}
}
return &HoverInformation{source: obj, comment: decl.Doc}
}
// extractFieldList recursively tries to extract a field list.
// If it is not found, nil is returned.
func extractFieldList(specType ast.Expr) *ast.FieldList {
switch t := specType.(type) {
case *ast.StructType:
return t.Fields
case *ast.InterfaceType:
return t.Methods
case *ast.ArrayType:
return extractFieldList(t.Elt)
case *ast.MapType:
// Map value has a greater chance to be a struct
if fields := extractFieldList(t.Value); fields != nil {
return fields
}
return extractFieldList(t.Key)
case *ast.ChanType:
return extractFieldList(t.Value)
}
return nil
}
// findFieldComment visits all fields in depth-first order and returns
// the comment of a field with passed position. If no comment is found,
// nil is returned.
func findFieldComment(pos token.Pos, fieldList *ast.FieldList) *ast.CommentGroup {
for _, field := range fieldList.List {
if field.Pos() == pos {
if field.Doc.Text() != "" {
return field.Doc
}
return field.Comment
}
if nestedFieldList := extractFieldList(field.Type); nestedFieldList != nil {
if c := findFieldComment(pos, nestedFieldList); c != nil {
return c
}
}
}
return nil
}
func FormatHover(h *HoverInformation, options *Options) (string, error) {
signature := h.Signature
if signature != "" && options.PreferredContentFormat == protocol.Markdown {
signature = fmt.Sprintf("```go\n%s\n```", signature)
}
switch options.HoverKind {
case SingleLine:
return h.SingleLine, nil
case NoDocumentation:
return signature, nil
case Structured:
b, err := json.Marshal(h)
if err != nil {
return "", err
}
return string(b), nil
}
link := formatLink(h, options)
switch options.HoverKind {
case SynopsisDocumentation:
doc := formatDoc(h.Synopsis, options)
return formatHover(options, signature, link, doc), nil
case FullDocumentation:
doc := formatDoc(h.FullDocumentation, options)
return formatHover(options, signature, link, doc), nil
}
return "", errors.Errorf("no hover for %v", h.source)
}
func formatLink(h *HoverInformation, options *Options) string {
if !options.LinksInHover || options.LinkTarget == "" || h.LinkPath == "" {
return ""
}
plainLink := BuildLink(options.LinkTarget, h.LinkPath, h.LinkAnchor)
switch options.PreferredContentFormat {
case protocol.Markdown:
return fmt.Sprintf("[`%s` on %s](%s)", h.symbolName, options.LinkTarget, plainLink)
case protocol.PlainText:
return ""
default:
return plainLink
}
}
// BuildLink constructs a link with the given target, path, and anchor.
func BuildLink(target, path, anchor string) string {
link := fmt.Sprintf("https://%s/%s", target, path)
if target == "pkg.go.dev" {
link += "?utm_source=gopls"
}
if anchor == "" {
return link
}
return link + "#" + anchor
}
func formatDoc(doc string, options *Options) string {
if options.PreferredContentFormat == protocol.Markdown {
return CommentToMarkdown(doc)
}
return doc
}
func formatHover(options *Options, x ...string) string {
var b strings.Builder
for i, el := range x {
if el != "" {
b.WriteString(el)
// Don't write out final newline.
if i == len(x) {
continue
}
// If any elements of the remainder of the list are non-empty,
// write a newline.
if anyNonEmpty(x[i+1:]) {
if options.PreferredContentFormat == protocol.Markdown {
b.WriteString("\n\n")
} else {
b.WriteRune('\n')
}
}
}
}
return b.String()
}
func anyNonEmpty(x []string) bool {
for _, el := range x {
if el != "" {
return true
}
}
return false
}