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// Copyright 2018 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 (
"bytes"
"context"
"fmt"
"go/ast"
"go/token"
"go/types"
"golang.org/x/tools/go/ast/astutil"
)
// IdentifierInfo holds information about an identifier in Go source.
type IdentifierInfo struct {
Name string
Range Range
File File
Type struct {
Range Range
Object types.Object
}
Declaration struct {
Range Range
Object types.Object
}
ident *ast.Ident
wasEmbeddedField bool
}
// Identifier returns identifier information for a position
// in a file, accounting for a potentially incomplete selector.
func Identifier(ctx context.Context, v View, f File, pos token.Pos) (*IdentifierInfo, error) {
if result, err := identifier(ctx, v, f, pos); err != nil || result != nil {
return result, err
}
// If the position is not an identifier but immediately follows
// an identifier or selector period (as is common when
// requesting a completion), use the path to the preceding node.
return identifier(ctx, v, f, pos-1)
}
func (i *IdentifierInfo) Hover(q types.Qualifier) (string, error) {
if q == nil {
fAST, err := i.File.GetAST()
if err != nil {
return "", err
}
pkg, err := i.File.GetPackage()
if err != nil {
return "", err
}
q = qualifier(fAST, pkg.Types, pkg.TypesInfo)
}
return types.ObjectString(i.Declaration.Object, q), nil
}
// identifier checks a single position for a potential identifier.
func identifier(ctx context.Context, v View, f File, pos token.Pos) (*IdentifierInfo, error) {
fAST, err := f.GetAST()
if err != nil {
return nil, err
}
pkg, err := f.GetPackage()
if err != nil {
return nil, err
}
path, _ := astutil.PathEnclosingInterval(fAST, pos, pos)
result := &IdentifierInfo{
File: f,
}
if path == nil {
return nil, fmt.Errorf("can't find node enclosing position")
}
switch node := path[0].(type) {
case *ast.Ident:
result.ident = node
case *ast.SelectorExpr:
result.ident = node.Sel
}
if result.ident == nil {
return nil, nil
}
for _, n := range path[1:] {
if field, ok := n.(*ast.Field); ok {
result.wasEmbeddedField = len(field.Names) == 0
}
}
result.Name = result.ident.Name
result.Range = Range{Start: result.ident.Pos(), End: result.ident.End()}
result.Declaration.Object = pkg.TypesInfo.ObjectOf(result.ident)
if result.Declaration.Object == nil {
return nil, fmt.Errorf("no object for ident %v", result.Name)
}
if result.wasEmbeddedField {
// The original position was on the embedded field declaration, so we
// try to dig out the type and jump to that instead.
if v, ok := result.Declaration.Object.(*types.Var); ok {
if n, ok := v.Type().(*types.Named); ok {
result.Declaration.Object = n.Obj()
}
}
}
if result.Declaration.Range, err = objToRange(ctx, v, result.Declaration.Object); err != nil {
return nil, err
}
typ := pkg.TypesInfo.TypeOf(result.ident)
if typ == nil {
return nil, fmt.Errorf("no type for %s", result.Name)
}
result.Type.Object = typeToObject(typ)
if result.Type.Object != nil {
if result.Type.Range, err = objToRange(ctx, v, result.Type.Object); err != nil {
return nil, err
}
}
return result, nil
}
func typeToObject(typ types.Type) types.Object {
switch typ := typ.(type) {
case *types.Named:
return typ.Obj()
case *types.Pointer:
return typeToObject(typ.Elem())
default:
return nil
}
}
func objToRange(ctx context.Context, v View, obj types.Object) (Range, error) {
p := obj.Pos()
if !p.IsValid() {
return Range{}, fmt.Errorf("invalid position for %v", obj.Name())
}
tok := v.FileSet().File(p)
pos := tok.Position(p)
if pos.Column == 1 {
// We do not have full position information because exportdata does not
// store the column. For now, we attempt to read the original source
// and find the identifier within the line. If we find it, we patch the
// column to match its offset.
//
// TODO: If we parse from source, we will never need this hack.
f, err := v.GetFile(ctx, ToURI(pos.Filename))
if err != nil {
goto Return
}
src, err := f.Read()
if err != nil {
goto Return
}
tok, err := f.GetToken()
if err != nil {
goto Return
}
start := lineStart(tok, pos.Line)
offset := tok.Offset(start)
col := bytes.Index(src[offset:], []byte(obj.Name()))
p = tok.Pos(offset + col)
}
Return:
return Range{
Start: p,
End: p + token.Pos(identifierLen(obj.Name())),
}, nil
}
// TODO: This needs to be fixed to address golang.org/issue/29149.
func identifierLen(ident string) int {
return len([]byte(ident))
}
// this functionality was borrowed from the analysisutil package
func lineStart(f *token.File, line int) token.Pos {
// Use binary search to find the start offset of this line.
//
// TODO(adonovan): eventually replace this function with the
// simpler and more efficient (*go/token.File).LineStart, added
// in go1.12.
min := 0 // inclusive
max := f.Size() // exclusive
for {
offset := (min + max) / 2
pos := f.Pos(offset)
posn := f.Position(pos)
if posn.Line == line {
return pos - (token.Pos(posn.Column) - 1)
}
if min+1 >= max {
return token.NoPos
}
if posn.Line < line {
min = offset
} else {
max = offset
}
}
}
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