rename.go

package gobfuscate

/*
	Copyright (c) 2009 The Go Authors. All rights reserved.

	Redistribution and use in source and binary forms, with or without
	modification, are permitted provided that the following conditions are
	met:

	* Redistributions of source code must retain the above copyright
	notice, this list of conditions and the following disclaimer.
	* Redistributions in binary form must reproduce the above
	copyright notice, this list of conditions and the following disclaimer
	in the documentation and/or other materials provided with the
	distribution.
	* Neither the name of Google Inc. nor the names of its
	contributors may be used to endorse or promote products derived from
	this software without specific prior written permission.

	THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

import (
	"bytes"
	"errors"
	"fmt"
	"go/ast"
	"go/build"
	"go/format"
	"go/parser"
	"go/token"
	"go/types"
	"io"
	"io/ioutil"
	"os"
	"os/exec"
	"path"
	"regexp"
	"sort"
	"strconv"
	"strings"

	"golang.org/x/tools/go/loader"
	"golang.org/x/tools/go/types/typeutil"
	"golang.org/x/tools/refactor/importgraph"
	"golang.org/x/tools/refactor/satisfy"
)

var (
	// Force enables patching of the source files even if conflicts were reported.
	// The resulting program may be ill-formed.
	// It may even cause gorename to crash.  TODO(adonovan): fix that.
	Force = true // This ensure we ignore any "DO NOT EDIT"s

	// Diff causes the tool to display diffs instead of rewriting files.
	Diff bool

	// DiffCmd specifies the diff command used by the -d feature.
	// (The command must accept a -u flag and two filename arguments.)
	DiffCmd = "diff"

	// ConflictError is returned by Main when it aborts the renaming due to conflicts.
	// (It is distinguished because the interesting errors are the conflicts themselves.)
	ConflictError = errors.New("renaming aborted due to conflicts")

	// Verbose enables extra logging.
	Verbose bool
)

var stdout io.Writer = os.Stdout

type renamer struct {
	iprog              *loader.Program
	objsToUpdate       map[types.Object]bool
	hadConflicts       bool
	from, to           string
	satisfyConstraints map[satisfy.Constraint]bool
	packages           map[*types.Package]*loader.PackageInfo // subset of iprog.AllPackages to inspect
	msets              typeutil.MethodSetCache
	changeMethods      bool
}

var reportError = func(posn token.Position, message string) {
	obfuscateLog.Errorf("%s: %s\n", posn, message)
}

// importName renames imports of fromPath within the package specified by info.
// If fromName is not empty, importName renames only imports as fromName.
// If the renaming would lead to a conflict, the file is left unchanged.
func importName(iprog *loader.Program, info *loader.PackageInfo, fromPath, fromName, to string) error {
	if fromName == to {
		return nil // no-op (e.g. rename x/foo to y/foo)
	}
	for _, f := range info.Files {
		var from types.Object
		for _, imp := range f.Imports {
			importPath, _ := strconv.Unquote(imp.Path.Value)
			importName := path.Base(importPath)
			if imp.Name != nil {
				importName = imp.Name.Name
			}
			if importPath == fromPath && (fromName == "" || importName == fromName) {
				from = info.Implicits[imp]
				break
			}
		}
		if from == nil {
			continue
		}
		r := renamer{
			iprog:        iprog,
			objsToUpdate: make(map[types.Object]bool),
			to:           to,
			packages:     map[*types.Package]*loader.PackageInfo{info.Pkg: info},
		}
		r.check(from)
		if r.hadConflicts {
			reportError(iprog.Fset.Position(f.Imports[0].Pos()), "skipping update of this file")
			continue // ignore errors; leave the existing name
		}
		if err := r.update(); err != nil {
			return err
		}
	}
	return nil
}

// Rename - Rename a symbol
func Rename(ctxt *build.Context, offsetFlag, fromFlag, to string) error {
	// -- Parse the -from or -offset specifier ----------------------------

	if (offsetFlag == "") == (fromFlag == "") {
		return fmt.Errorf("exactly one of the -from and -offset flags must be specified")
	}

	if !isValidIdentifier(to) {
		return fmt.Errorf("-to %q: not a valid identifier", to)
	}

	if Diff {
		defer func(saved func(string, []byte) error) { writeFile = saved }(writeFile)
		writeFile = diff
	}

	var spec *spec
	var err error
	if fromFlag != "" {
		spec, err = parseFromFlag(ctxt, fromFlag)
	} else {
		spec, err = parseOffsetFlag(ctxt, offsetFlag)
	}
	if err != nil {
		return err
	}

	if spec.fromName == to {
		return fmt.Errorf("the old and new names are the same: %s", to)
	}

	// -- Load the program consisting of the initial package  -------------

	iprog, err := loadProgram(ctxt, map[string]bool{spec.pkg: true})
	if err != nil {
		return err
	}

	fromObjects, err := findFromObjects(iprog, spec)
	if err != nil {
		return err
	}

	// -- Load a larger program, for global renamings ---------------------

	if requiresGlobalRename(fromObjects, to) {
		// For a local refactoring, we needn't load more
		// packages, but if the renaming affects the package's
		// API, we we must load all packages that depend on the
		// package defining the object, plus their tests.

		if Verbose {
			obfuscateLog.Info("Potentially global renaming; scanning workspace...")
		}

		// Scan the workspace and build the import graph.
		_, rev, errors := importgraph.Build(ctxt)
		if len(errors) > 0 {
			// With a large GOPATH tree, errors are inevitable.
			// Report them but proceed.
			fmt.Fprintf(os.Stderr, "While scanning Go workspace:\n")
			for path, err := range errors {
				fmt.Fprintf(os.Stderr, "Package %q: %s.\n", path, err)
			}
		}

		// Enumerate the set of potentially affected packages.
		affectedPackages := make(map[string]bool)
		for _, obj := range fromObjects {
			// External test packages are never imported,
			// so they will never appear in the graph.
			for path := range rev.Search(obj.Pkg().Path()) {
				affectedPackages[path] = true
			}
		}

		// TODO(adonovan): allow the user to specify the scope,
		// or -ignore patterns?  Computing the scope when we
		// don't (yet) support inputs containing errors can make
		// the tool rather brittle.

		// Re-load the larger program.
		iprog, err = loadProgram(ctxt, affectedPackages)
		if err != nil {
			return err
		}

		fromObjects, err = findFromObjects(iprog, spec)
		if err != nil {
			return err
		}
	}

	// -- Do the renaming -------------------------------------------------

	r := renamer{
		iprog:        iprog,
		objsToUpdate: make(map[types.Object]bool),
		from:         spec.fromName,
		to:           to,
		packages:     make(map[*types.Package]*loader.PackageInfo),
	}

	// A renaming initiated at an interface method indicates the
	// intention to rename abstract and concrete methods as needed
	// to preserve assignability.
	for _, obj := range fromObjects {
		if obj, ok := obj.(*types.Func); ok {
			recv := obj.Type().(*types.Signature).Recv()
			if recv != nil && isInterface(recv.Type().Underlying()) {
				r.changeMethods = true
				break
			}
		}
	}

	// Only the initially imported packages (iprog.Imported) and
	// their external tests (iprog.Created) should be inspected or
	// modified, as only they have type-checked functions bodies.
	// The rest are just dependencies, needed only for package-level
	// type information.
	for _, info := range iprog.Imported {
		r.packages[info.Pkg] = info
	}
	for _, info := range iprog.Created { // (tests)
		r.packages[info.Pkg] = info
	}

	for _, from := range fromObjects {
		r.check(from)
	}
	if r.hadConflicts && !Force {
		return ConflictError
	}
	return r.update()
}

// loadProgram loads the specified set of packages (plus their tests)
// and all their dependencies, from source, through the specified build
// context.  Only packages in pkgs will have their functions bodies typechecked.
func loadProgram(ctxt *build.Context, pkgs map[string]bool) (*loader.Program, error) {
	conf := loader.Config{
		Build:      ctxt,
		ParserMode: parser.ParseComments,

		// TODO(adonovan): enable this.  Requires making a lot of code more robust!
		AllowErrors: false,
	}
	// Optimization: don't type-check the bodies of functions in our
	// dependencies, since we only need exported package members.
	conf.TypeCheckFuncBodies = func(p string) bool {
		return pkgs[p] || pkgs[strings.TrimSuffix(p, "_test")]
	}

	if Verbose {
		var list []string
		for pkg := range pkgs {
			list = append(list, pkg)
		}
		sort.Strings(list)
		for _, pkg := range list {
			obfuscateLog.Infof("Loading package: %s", pkg)
		}
	}

	for pkg := range pkgs {
		conf.ImportWithTests(pkg)
	}

	// Ideally we would just return conf.Load() here, but go/types
	// reports certain "soft" errors that gc does not (Go issue 14596).
	// As a workaround, we set AllowErrors=true and then duplicate
	// the loader's error checking but allow soft errors.
	// It would be nice if the loader API permitted "AllowErrors: soft".
	conf.AllowErrors = true
	prog, err := conf.Load()
	if err != nil {
		return nil, err
	}

	var errpkgs []string
	// Report hard errors in indirectly imported packages.
	for _, info := range prog.AllPackages {
		if containsHardErrors(info.Errors) {
			errpkgs = append(errpkgs, info.Pkg.Path())
		}
	}
	if errpkgs != nil {
		var more string
		if len(errpkgs) > 3 {
			more = fmt.Sprintf(" and %d more", len(errpkgs)-3)
			errpkgs = errpkgs[:3]
		}
		return nil, fmt.Errorf("couldn't load packages due to errors: %s%s",
			strings.Join(errpkgs, ", "), more)
	}
	return prog, nil
}

func containsHardErrors(errors []error) bool {
	for _, err := range errors {
		if err, ok := err.(types.Error); ok && err.Soft {
			continue
		}
		return true
	}
	return false
}

// requiresGlobalRename reports whether this renaming could potentially
// affect other packages in the Go workspace.
func requiresGlobalRename(fromObjects []types.Object, to string) bool {
	var tfm bool
	for _, from := range fromObjects {
		if from.Exported() {
			return true
		}
		switch objectKind(from) {
		case "type", "field", "method":
			tfm = true
		}
	}
	if ast.IsExported(to) && tfm {
		// A global renaming may be necessary even if we're
		// exporting a previous unexported name, since if it's
		// the name of a type, field or method, this could
		// change selections in other packages.
		// (We include "type" in this list because a type
		// used as an embedded struct field entails a field
		// renaming.)
		return true
	}
	return false
}

// update updates the input files.
func (r *renamer) update() error {
	// We use token.File, not filename, since a file may appear to
	// belong to multiple packages and be parsed more than once.
	// token.File captures this distinction; filename does not.

	var nidents int
	var filesToUpdate = make(map[*token.File]bool)
	docRegexp := regexp.MustCompile(`\b` + r.from + `\b`)
	for _, info := range r.packages {
		// Mutate the ASTs and note the filenames.
		for id, obj := range info.Defs {
			if r.objsToUpdate[obj] {
				nidents++
				id.Name = r.to
				filesToUpdate[r.iprog.Fset.File(id.Pos())] = true
				// Perform the rename in doc comments too.
				if doc := r.docComment(id); doc != nil {
					for _, comment := range doc.List {
						comment.Text = docRegexp.ReplaceAllString(comment.Text, r.to)
					}
				}
			}
		}

		for id, obj := range info.Uses {
			if r.objsToUpdate[obj] {
				nidents++
				id.Name = r.to
				filesToUpdate[r.iprog.Fset.File(id.Pos())] = true
			}
		}
	}

	// Renaming not supported if cgo files are affected.
	var generatedFileNames []string
	for _, info := range r.packages {
		for _, f := range info.Files {
			tokenFile := r.iprog.Fset.File(f.Pos())
			if filesToUpdate[tokenFile] && generated(f, tokenFile) {
				generatedFileNames = append(generatedFileNames, tokenFile.Name())
			}
		}
	}
	if !Force && len(generatedFileNames) > 0 {
		return fmt.Errorf("refusing to modify generated file%s containing DO NOT EDIT marker: %v", plural(len(generatedFileNames)), generatedFileNames)
	}

	// Write affected files.
	var nerrs, npkgs int
	for _, info := range r.packages {
		first := true
		for _, f := range info.Files {
			tokenFile := r.iprog.Fset.File(f.Pos())
			if filesToUpdate[tokenFile] {
				if first {
					npkgs++
					first = false
					if Verbose {
						obfuscateLog.Infof("Updating package %s", info.Pkg.Path())
					}
				}

				filename := tokenFile.Name()
				var buf bytes.Buffer
				if err := format.Node(&buf, r.iprog.Fset, f); err != nil {
					obfuscateLog.Infof("failed to pretty-print syntax tree: %v", err)
					nerrs++
					continue
				}
				if err := writeFile(filename, buf.Bytes()); err != nil {
					obfuscateLog.Error(err)
					nerrs++
				}
			}
		}
	}
	if !Diff {
		obfuscateLog.Infof("Renamed %d occurrence%s in %d file%s in %d package%s.\n",
			nidents, plural(nidents),
			len(filesToUpdate), plural(len(filesToUpdate)),
			npkgs, plural(npkgs))
	}
	if nerrs > 0 {
		return fmt.Errorf("failed to rewrite %d file%s", nerrs, plural(nerrs))
	}
	return nil
}

// docComment returns the doc for an identifier.
func (r *renamer) docComment(id *ast.Ident) *ast.CommentGroup {
	_, nodes, _ := r.iprog.PathEnclosingInterval(id.Pos(), id.End())
	for _, node := range nodes {
		switch decl := node.(type) {
		case *ast.FuncDecl:
			return decl.Doc
		case *ast.Field:
			return decl.Doc
		case *ast.GenDecl:
			return decl.Doc
		// For {Type,Value}Spec, if the doc on the spec is absent,
		// search for the enclosing GenDecl
		case *ast.TypeSpec:
			if decl.Doc != nil {
				return decl.Doc
			}
		case *ast.ValueSpec:
			if decl.Doc != nil {
				return decl.Doc
			}
		case *ast.Ident:
		default:
			return nil
		}
	}
	return nil
}

func plural(n int) string {
	if n != 1 {
		return "s"
	}
	return ""
}

// writeFile is a seam for testing and for the -d flag.
var writeFile = reallyWriteFile

func reallyWriteFile(filename string, content []byte) error {
	return ioutil.WriteFile(filename, content, 0644)
}

func diff(filename string, content []byte) error {
	renamed := fmt.Sprintf("%s.%d.renamed", filename, os.Getpid())
	if err := ioutil.WriteFile(renamed, content, 0644); err != nil {
		return err
	}
	defer os.Remove(renamed)

	diff, err := exec.Command(DiffCmd, "-u", filename, renamed).CombinedOutput()
	if len(diff) > 0 {
		// diff exits with a non-zero status when the files don't match.
		// Ignore that failure as long as we get output.
		stdout.Write(diff)
		return nil
	}
	if err != nil {
		return fmt.Errorf("computing diff: %v", err)
	}
	return nil
}