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// Copyright 2013 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 astutil contains common utilities for working with the Go AST.
package astutil // import "golang.org/x/tools/go/ast/astutil"
import (
"fmt"
"go/ast"
"go/token"
"strconv"
"strings"
)
// AddImport adds the import path to the file f, if absent.
func AddImport(fset *token.FileSet, f *ast.File, path string) (added bool) {
return AddNamedImport(fset, f, "", path)
}
// AddNamedImport adds the import with the given name and path to the file f, if absent.
// If name is not empty, it is used to rename the import.
//
// For example, calling
// AddNamedImport(fset, f, "pathpkg", "path")
// adds
// import pathpkg "path"
func AddNamedImport(fset *token.FileSet, f *ast.File, name, path string) (added bool) {
if imports(f, name, path) {
return false
}
newImport := &ast.ImportSpec{
Path: &ast.BasicLit{
Kind: token.STRING,
Value: strconv.Quote(path),
},
}
if name != "" {
newImport.Name = &ast.Ident{Name: name}
}
// Find an import decl to add to.
// The goal is to find an existing import
// whose import path has the longest shared
// prefix with path.
var (
bestMatch = -1 // length of longest shared prefix
lastImport = -1 // index in f.Decls of the file's final import decl
impDecl *ast.GenDecl // import decl containing the best match
impIndex = -1 // spec index in impDecl containing the best match
isThirdPartyPath = isThirdParty(path)
)
for i, decl := range f.Decls {
gen, ok := decl.(*ast.GenDecl)
if ok && gen.Tok == token.IMPORT {
lastImport = i
// Do not add to import "C", to avoid disrupting the
// association with its doc comment, breaking cgo.
if declImports(gen, "C") {
continue
}
// Match an empty import decl if that's all that is available.
if len(gen.Specs) == 0 && bestMatch == -1 {
impDecl = gen
}
// Compute longest shared prefix with imports in this group and find best
// matched import spec.
// 1. Always prefer import spec with longest shared prefix.
// 2. While match length is 0,
// - for stdlib package: prefer first import spec.
// - for third party package: prefer first third party import spec.
// We cannot use last import spec as best match for third party package
// because grouped imports are usually placed last by goimports -local
// flag.
// See issue #19190.
seenAnyThirdParty := false
for j, spec := range gen.Specs {
impspec := spec.(*ast.ImportSpec)
p := importPath(impspec)
n := matchLen(p, path)
if n > bestMatch || (bestMatch == 0 && !seenAnyThirdParty && isThirdPartyPath) {
bestMatch = n
impDecl = gen
impIndex = j
}
seenAnyThirdParty = seenAnyThirdParty || isThirdParty(p)
}
}
}
// If no import decl found, add one after the last import.
if impDecl == nil {
impDecl = &ast.GenDecl{
Tok: token.IMPORT,
}
if lastImport >= 0 {
impDecl.TokPos = f.Decls[lastImport].End()
} else {
// There are no existing imports.
// Our new import, preceded by a blank line, goes after the package declaration
// and after the comment, if any, that starts on the same line as the
// package declaration.
impDecl.TokPos = f.Package
file := fset.File(f.Package)
pkgLine := file.Line(f.Package)
for _, c := range f.Comments {
if file.Line(c.Pos()) > pkgLine {
break
}
// +2 for a blank line
impDecl.TokPos = c.End() + 2
}
}
f.Decls = append(f.Decls, nil)
copy(f.Decls[lastImport+2:], f.Decls[lastImport+1:])
f.Decls[lastImport+1] = impDecl
}
// Insert new import at insertAt.
insertAt := 0
if impIndex >= 0 {
// insert after the found import
insertAt = impIndex + 1
}
impDecl.Specs = append(impDecl.Specs, nil)
copy(impDecl.Specs[insertAt+1:], impDecl.Specs[insertAt:])
impDecl.Specs[insertAt] = newImport
pos := impDecl.Pos()
if insertAt > 0 {
// If there is a comment after an existing import, preserve the comment
// position by adding the new import after the comment.
if spec, ok := impDecl.Specs[insertAt-1].(*ast.ImportSpec); ok && spec.Comment != nil {
pos = spec.Comment.End()
} else {
// Assign same position as the previous import,
// so that the sorter sees it as being in the same block.
pos = impDecl.Specs[insertAt-1].Pos()
}
}
if newImport.Name != nil {
newImport.Name.NamePos = pos
}
newImport.Path.ValuePos = pos
newImport.EndPos = pos
// Clean up parens. impDecl contains at least one spec.
if len(impDecl.Specs) == 1 {
// Remove unneeded parens.
impDecl.Lparen = token.NoPos
} else if !impDecl.Lparen.IsValid() {
// impDecl needs parens added.
impDecl.Lparen = impDecl.Specs[0].Pos()
}
f.Imports = append(f.Imports, newImport)
if len(f.Decls) <= 1 {
return true
}
// Merge all the import declarations into the first one.
var first *ast.GenDecl
for i := 0; i < len(f.Decls); i++ {
decl := f.Decls[i]
gen, ok := decl.(*ast.GenDecl)
if !ok || gen.Tok != token.IMPORT || declImports(gen, "C") {
continue
}
if first == nil {
first = gen
continue // Don't touch the first one.
}
// We now know there is more than one package in this import
// declaration. Ensure that it ends up parenthesized.
first.Lparen = first.Pos()
// Move the imports of the other import declaration to the first one.
for _, spec := range gen.Specs {
spec.(*ast.ImportSpec).Path.ValuePos = first.Pos()
first.Specs = append(first.Specs, spec)
}
f.Decls = append(f.Decls[:i], f.Decls[i+1:]...)
i--
}
return true
}
func isThirdParty(importPath string) bool {
// Third party package import path usually contains "." (".com", ".org", ...)
// This logic is taken from golang.org/x/tools/imports package.
return strings.Contains(importPath, ".")
}
// DeleteImport deletes the import path from the file f, if present.
// If there are duplicate import declarations, all matching ones are deleted.
func DeleteImport(fset *token.FileSet, f *ast.File, path string) (deleted bool) {
return DeleteNamedImport(fset, f, "", path)
}
// DeleteNamedImport deletes the import with the given name and path from the file f, if present.
// If there are duplicate import declarations, all matching ones are deleted.
func DeleteNamedImport(fset *token.FileSet, f *ast.File, name, path string) (deleted bool) {
var delspecs []*ast.ImportSpec
var delcomments []*ast.CommentGroup
// Find the import nodes that import path, if any.
for i := 0; i < len(f.Decls); i++ {
decl := f.Decls[i]
gen, ok := decl.(*ast.GenDecl)
if !ok || gen.Tok != token.IMPORT {
continue
}
for j := 0; j < len(gen.Specs); j++ {
spec := gen.Specs[j]
impspec := spec.(*ast.ImportSpec)
if importName(impspec) != name || importPath(impspec) != path {
continue
}
// We found an import spec that imports path.
// Delete it.
delspecs = append(delspecs, impspec)
deleted = true
copy(gen.Specs[j:], gen.Specs[j+1:])
gen.Specs = gen.Specs[:len(gen.Specs)-1]
// If this was the last import spec in this decl,
// delete the decl, too.
if len(gen.Specs) == 0 {
copy(f.Decls[i:], f.Decls[i+1:])
f.Decls = f.Decls[:len(f.Decls)-1]
i--
break
} else if len(gen.Specs) == 1 {
if impspec.Doc != nil {
delcomments = append(delcomments, impspec.Doc)
}
if impspec.Comment != nil {
delcomments = append(delcomments, impspec.Comment)
}
for _, cg := range f.Comments {
// Found comment on the same line as the import spec.
if cg.End() < impspec.Pos() && fset.Position(cg.End()).Line == fset.Position(impspec.Pos()).Line {
delcomments = append(delcomments, cg)
break
}
}
spec := gen.Specs[0].(*ast.ImportSpec)
// Move the documentation right after the import decl.
if spec.Doc != nil {
for fset.Position(gen.TokPos).Line+1 < fset.Position(spec.Doc.Pos()).Line {
fset.File(gen.TokPos).MergeLine(fset.Position(gen.TokPos).Line)
}
}
for _, cg := range f.Comments {
if cg.End() < spec.Pos() && fset.Position(cg.End()).Line == fset.Position(spec.Pos()).Line {
for fset.Position(gen.TokPos).Line+1 < fset.Position(spec.Pos()).Line {
fset.File(gen.TokPos).MergeLine(fset.Position(gen.TokPos).Line)
}
break
}
}
}
if j > 0 {
lastImpspec := gen.Specs[j-1].(*ast.ImportSpec)
lastLine := fset.Position(lastImpspec.Path.ValuePos).Line
line := fset.Position(impspec.Path.ValuePos).Line
// We deleted an entry but now there may be
// a blank line-sized hole where the import was.
if line-lastLine > 1 || !gen.Rparen.IsValid() {
// There was a blank line immediately preceding the deleted import,
// so there's no need to close the hole. The right parenthesis is
// invalid after AddImport to an import statement without parenthesis.
// Do nothing.
} else if line != fset.File(gen.Rparen).LineCount() {
// There was no blank line. Close the hole.
fset.File(gen.Rparen).MergeLine(line)
}
}
j--
}
}
// Delete imports from f.Imports.
for i := 0; i < len(f.Imports); i++ {
imp := f.Imports[i]
for j, del := range delspecs {
if imp == del {
copy(f.Imports[i:], f.Imports[i+1:])
f.Imports = f.Imports[:len(f.Imports)-1]
copy(delspecs[j:], delspecs[j+1:])
delspecs = delspecs[:len(delspecs)-1]
i--
break
}
}
}
// Delete comments from f.Comments.
for i := 0; i < len(f.Comments); i++ {
cg := f.Comments[i]
for j, del := range delcomments {
if cg == del {
copy(f.Comments[i:], f.Comments[i+1:])
f.Comments = f.Comments[:len(f.Comments)-1]
copy(delcomments[j:], delcomments[j+1:])
delcomments = delcomments[:len(delcomments)-1]
i--
break
}
}
}
if len(delspecs) > 0 {
panic(fmt.Sprintf("deleted specs from Decls but not Imports: %v", delspecs))
}
return
}
// RewriteImport rewrites any import of path oldPath to path newPath.
func RewriteImport(fset *token.FileSet, f *ast.File, oldPath, newPath string) (rewrote bool) {
for _, imp := range f.Imports {
if importPath(imp) == oldPath {
rewrote = true
// record old End, because the default is to compute
// it using the length of imp.Path.Value.
imp.EndPos = imp.End()
imp.Path.Value = strconv.Quote(newPath)
}
}
return
}
// UsesImport reports whether a given import is used.
func UsesImport(f *ast.File, path string) (used bool) {
spec := importSpec(f, path)
if spec == nil {
return
}
name := spec.Name.String()
switch name {
case "<nil>":
// If the package name is not explicitly specified,
// make an educated guess. This is not guaranteed to be correct.
lastSlash := strings.LastIndex(path, "/")
if lastSlash == -1 {
name = path
} else {
name = path[lastSlash+1:]
}
case "_", ".":
// Not sure if this import is used - err on the side of caution.
return true
}
ast.Walk(visitFn(func(n ast.Node) {
sel, ok := n.(*ast.SelectorExpr)
if ok && isTopName(sel.X, name) {
used = true
}
}), f)
return
}
type visitFn func(node ast.Node)
func (fn visitFn) Visit(node ast.Node) ast.Visitor {
fn(node)
return fn
}
// imports reports whether f has an import with the specified name and path.
func imports(f *ast.File, name, path string) bool {
for _, s := range f.Imports {
if importName(s) == name && importPath(s) == path {
return true
}
}
return false
}
// importSpec returns the import spec if f imports path,
// or nil otherwise.
func importSpec(f *ast.File, path string) *ast.ImportSpec {
for _, s := range f.Imports {
if importPath(s) == path {
return s
}
}
return nil
}
// importName returns the name of s,
// or "" if the import is not named.
func importName(s *ast.ImportSpec) string {
if s.Name == nil {
return ""
}
return s.Name.Name
}
// importPath returns the unquoted import path of s,
// or "" if the path is not properly quoted.
func importPath(s *ast.ImportSpec) string {
t, err := strconv.Unquote(s.Path.Value)
if err != nil {
return ""
}
return t
}
// declImports reports whether gen contains an import of path.
func declImports(gen *ast.GenDecl, path string) bool {
if gen.Tok != token.IMPORT {
return false
}
for _, spec := range gen.Specs {
impspec := spec.(*ast.ImportSpec)
if importPath(impspec) == path {
return true
}
}
return false
}
// matchLen returns the length of the longest path segment prefix shared by x and y.
func matchLen(x, y string) int {
n := 0
for i := 0; i < len(x) && i < len(y) && x[i] == y[i]; i++ {
if x[i] == '/' {
n++
}
}
return n
}
// isTopName returns true if n is a top-level unresolved identifier with the given name.
func isTopName(n ast.Expr, name string) bool {
id, ok := n.(*ast.Ident)
return ok && id.Name == name && id.Obj == nil
}
// Imports returns the file imports grouped by paragraph.
func Imports(fset *token.FileSet, f *ast.File) [][]*ast.ImportSpec {
var groups [][]*ast.ImportSpec
for _, decl := range f.Decls {
genDecl, ok := decl.(*ast.GenDecl)
if !ok || genDecl.Tok != token.IMPORT {
break
}
group := []*ast.ImportSpec{}
var lastLine int
for _, spec := range genDecl.Specs {
importSpec := spec.(*ast.ImportSpec)
pos := importSpec.Path.ValuePos
line := fset.Position(pos).Line
if lastLine > 0 && pos > 0 && line-lastLine > 1 {
groups = append(groups, group)
group = []*ast.ImportSpec{}
}
group = append(group, importSpec)
lastLine = line
}
groups = append(groups, group)
}
return groups
}
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