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cmd/gorename: a precise, type-aware renaming tool for Go identifiers.

Browse Source 
See the usage message in main.go for orientation.

To the best of my knowledge, the tool implements all required
soundness checks, except:
- the dynamic behaviour of reflection is obviously undecidable.
- it rejects method renamings that change the "implements" relation.
  It should probably be more aggressive.
- actually it only checks the part of the "implements" relation
  needed for compilation.  Understanding the dynamic behaviour
  of interfaces is obviously undecidable.
- a couple of minor gaps are indicated by TODO comments.

Also:
- Emacs integration.
- tests of all safety checks and (some) successful rewrites.

LGTM=dominik.honnef, sameer
R=gri, sameer, dominik.honnef
CC=golang-codereviews
https://golang.org/cl/139150044
This commit is contained in:
Alan Donovan 2014-09-23 10:23:04 -04:00
parent aba8625c37
commit 74021b4175
7 changed files with 2671 additions and 0 deletions
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137
cmd/gorename/main.go Normal file
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// The gorename command performs precise type-safe renaming of
// identifiers in Go source code. See the -help message or Usage
// constant for details.
package main
import (
"flag"
"fmt"
"go/build"
"os"
"runtime"
"code.google.com/p/go.tools/refactor/rename"
)
var (
offsetFlag = flag.String("offset", "", "file and byte offset of identifier to be renamed, e.g. 'file.go:#123'. For use by editors.")
fromFlag = flag.String("from", "", "identifier to be renamed; see -help for formats")
toFlag = flag.String("to", "", "new name for identifier")
helpFlag = flag.Bool("help", false, "show usage message")
)
func init() {
flag.BoolVar(&rename.Force, "force", false, "proceed, even if conflicts were reported")
flag.BoolVar(&rename.DryRun, "dryrun", false, "show the change, but do not apply it")
flag.BoolVar(&rename.Verbose, "v", false, "print verbose information")
// If $GOMAXPROCS isn't set, use the full capacity of the machine.
// For small machines, use at least 4 threads.
if os.Getenv("GOMAXPROCS") == "" {
n := runtime.NumCPU()
if n < 4 {
n = 4
}
runtime.GOMAXPROCS(n)
}
}
const Usage = `gorename: precise type-safe renaming of identifiers in Go source code.
Usage:
gorename (-from <spec> | -offset <file>:#<byte-offset>) -to <name> [-force]
You must specify the object (named entity) to rename using the -offset
or -from flag. Exactly one must be specified.
Flags:
-offset specifies the filename and byte offset of an identifier to rename.
This form is intended for use by text editors.
-from specifies the object to rename using a query notation;
This form is intended for interactive use at the command line.
` + rename.FromFlagUsage + `
-to the new name.
-force causes the renaming to proceed even if conflicts were reported.
The resulting program may be ill-formed, or experience a change
in behaviour.
WARNING: this flag may even cause the renaming tool to crash.
(In due course this bug will be fixed by moving certain
analyses into the type-checker.)
-v enables verbose logging.
gorename automatically computes the set of packages that might be
affected. For a local renaming, this is just the package specified by
-from or -offset, but for a potentially exported name, gorename scans
the workspace ($GOROOT and $GOPATH).
gorename rejects any renaming that would create a conflict at the point
of declaration, or a reference conflict (ambiguity or shadowing), or
anything else that could cause the resulting program not to compile.
Currently, it also rejects any method renaming that would change the
assignability relation between types and interfaces.
Examples:
% gorename -offset file.go:#123 -to foo
Rename the object whose identifer is at byte offset 123 within file file.go.
% gorename -from '(bytes.Buffer).Len' -to Size
Rename the "Len" method of the *bytes.Buffer type to "Size".
---- TODO ----
Correctness:
- implement remaining safety checks.
- handle dot imports correctly
- document limitations (reflection, 'implements' guesswork).
- sketch a proof of exhaustiveness.
Features:
- support running on programs containing errors (loader.Config.AllowErrors)
- allow users to specify a scope other than "global" (to avoid being
stuck by neglected packages in $GOPATH that don't build).
- support renaming the package clause (no object)
- support renaming an import path (no ident or object)
(requires filesystem + SCM updates).
- detect and reject edits to autogenerated files (cgo, protobufs)
and optionally $GOROOT packages.
- report all conflicts, or at least all qualitatively distinct ones.
Sometimes we stop to avoid redundancy, but
it may give a disproportionate sense of safety in -force mode.
- support renaming all instances of a pattern, e.g.
all receiver vars of a given type,
all local variables of a given type,
all PkgNames for a given package.
- emit JSON output for other editors and tools.
- integration support for editors other than Emacs.
`
func main() {
flag.Parse()
if len(flag.Args()) > 0 {
fmt.Fprintf(os.Stderr, "Error: surplus arguments.\n")
os.Exit(1)
}
if *helpFlag || (*offsetFlag == "" && *fromFlag == "" && *toFlag == "") {
fmt.Println(Usage)
return
}
if err := rename.Main(&build.Default, *offsetFlag, *fromFlag, *toFlag); err != nil {
if err != rename.ConflictError {
fmt.Fprintf(os.Stderr, "Error: %s.\n", err)
}
os.Exit(1)
}
}

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refactor/rename/check.go Normal file
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// Copyright 2014 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 rename
// This file defines the safety checks for each kind of renaming.
import (
"fmt"
"go/ast"
"go/token"
"code.google.com/p/go.tools/go/loader"
"code.google.com/p/go.tools/go/types"
"code.google.com/p/go.tools/refactor/lexical"
"code.google.com/p/go.tools/refactor/satisfy"
)
// errorf reports an error (e.g. conflict) and prevents file modification.
func (r *renamer) errorf(pos token.Pos, format string, args ...interface{}) {
r.hadConflicts = true
reportError(r.iprog.Fset.Position(pos), fmt.Sprintf(format, args...))
}
// check performs safety checks of the renaming of the 'from' object to r.to.
func (r *renamer) check(from types.Object) {
if r.objsToUpdate[from] {
return
}
r.objsToUpdate[from] = true
// NB: order of conditions is important.
if from_, ok := from.(*types.PkgName); ok {
r.checkInFileBlock(from_)
} else if from_, ok := from.(*types.Label); ok {
r.checkLabel(from_)
} else if isPackageLevel(from) {
r.checkInPackageBlock(from)
} else if v, ok := from.(*types.Var); ok && v.IsField() {
r.checkStructField(v)
} else if f, ok := from.(*types.Func); ok && f.Type().(*types.Signature).Recv() != nil {
r.checkMethod(f)
} else if isLocal(from) {
r.checkInLocalScope(from)
} else {
r.errorf(from.Pos(), "unexpected %s object %q (please report a bug)\n",
objectKind(from), from)
}
}
// checkInFileBlock performs safety checks for renames of objects in the file block,
// i.e. imported package names.
func (r *renamer) checkInFileBlock(from *types.PkgName) {
// Check import name is not "init".
if r.to == "init" {
r.errorf(from.Pos(), "%q is not a valid imported package name", r.to)
}
// Check for conflicts between file and package block.
if prev := from.Pkg().Scope().Lookup(r.to); prev != nil {
r.errorf(from.Pos(), "renaming this %s %q to %q would conflict",
objectKind(from), from.Name(), r.to)
r.errorf(prev.Pos(), "\twith this package member %s",
objectKind(prev))
return // since checkInPackageBlock would report redundant errors
}
// Check for conflicts in lexical scope.
r.checkInLexicalScope(from, r.packages[from.Pkg()])
// Finally, modify ImportSpec syntax to add or remove the Name as needed.
info, path, _ := r.iprog.PathEnclosingInterval(from.Pos(), from.Pos())
if from.Imported().Name() == r.to {
// ImportSpec.Name not needed
path[1].(*ast.ImportSpec).Name = nil
} else {
// ImportSpec.Name needed
if spec := path[1].(*ast.ImportSpec); spec.Name == nil {
spec.Name = &ast.Ident{NamePos: spec.Path.Pos(), Name: r.to}
info.Defs[spec.Name] = from
}
}
}
// checkInPackageBlock performs safety checks for renames of
// func/var/const/type objects in the package block.
func (r *renamer) checkInPackageBlock(from types.Object) {
// Check that there are no references to the name from another
// package if the renaming would make it unexported.
if ast.IsExported(from.Name()) && !ast.IsExported(r.to) {
for pkg, info := range r.packages {
if pkg == from.Pkg() {
continue
}
if id := someUse(info, from); id != nil &&
!r.checkExport(id, pkg, from) {
break
}
}
}
info := r.packages[from.Pkg()]
lexinfo := lexical.Structure(r.iprog.Fset, from.Pkg(), &info.Info, info.Files)
// Check that in the package block, "init" is a function, and never referenced.
if r.to == "init" {
kind := objectKind(from)
if kind == "func" {
// Reject if intra-package references to it exist.
if refs := lexinfo.Refs[from]; len(refs) > 0 {
r.errorf(from.Pos(),
"renaming this func %q to %q would make it a package initializer",
from.Name(), r.to)
r.errorf(refs[0].Id.Pos(), "\tbut references to it exist")
}
} else {
r.errorf(from.Pos(), "you cannot have a %s at package level named %q",
kind, r.to)
}
}
// Check for conflicts between package block and all file blocks.
for _, f := range info.Files {
if prev, b := lexinfo.Blocks[f].Lookup(r.to); b == lexinfo.Blocks[f] {
r.errorf(from.Pos(), "renaming this %s %q to %q would conflict",
objectKind(from), from.Name(), r.to)
r.errorf(prev.Pos(), "\twith this %s",
objectKind(prev))
return // since checkInPackageBlock would report redundant errors
}
}
// Check for conflicts in lexical scope.
if from.Exported() {
for _, info := range r.packages {
r.checkInLexicalScope(from, info)
}
} else {
r.checkInLexicalScope(from, info)
}
}
func (r *renamer) checkInLocalScope(from types.Object) {
info := r.packages[from.Pkg()]
// Is this object an implicit local var for a type switch?
// Each case has its own var, whose position is the decl of y,
// but Ident in that decl does not appear in the Uses map.
//
// switch y := x.(type) { // Defs[Ident(y)] is undefined
// case int: print(y) // Implicits[CaseClause(int)] = Var(y_int)
// case string: print(y) // Implicits[CaseClause(string)] = Var(y_string)
// }
//
var isCaseVar bool
for syntax, obj := range info.Implicits {
if _, ok := syntax.(*ast.CaseClause); ok && obj.Pos() == from.Pos() {
isCaseVar = true
r.check(obj)
}
}
r.checkInLexicalScope(from, info)
// Finally, if this was a type switch, change the variable y.
if isCaseVar {
_, path, _ := r.iprog.PathEnclosingInterval(from.Pos(), from.Pos())
path[0].(*ast.Ident).Name = r.to // path is [Ident AssignStmt TypeSwitchStmt...]
}
}
// checkInLexicalScope performs safety checks that a renaming does not
// change the lexical reference structure of the specified package.
//
// For objects in lexical scope, there are three kinds of conflicts:
// same-, sub-, and super-block conflicts. We will illustrate all three
// using this example:
//
// var x int
// var z int
//
// func f(y int) {
// print(x)
// print(y)
// }
//
// Renaming x to z encounters a SAME-BLOCK CONFLICT, because an object
// with the new name already exists, defined in the same lexical block
// as the old object.
//
// Renaming x to y encounters a SUB-BLOCK CONFLICT, because there exists
// a reference to x from within (what would become) a hole in its scope.
// The definition of y in an (inner) sub-block would cast a shadow in
// the scope of the renamed variable.
//
// Renaming y to x encounters a SUPER-BLOCK CONFLICT. This is the
// converse situation: there is an existing definition of the new name
// (x) in an (enclosing) super-block, and the renaming would create a
// hole in its scope, within which there exist references to it. The
// new name casts a shadow in scope of the existing definition of x in
// the super-block.
//
// Removing the old name (and all references to it) is always safe, and
// requires no checks.
//
func (r *renamer) checkInLexicalScope(from types.Object, info *loader.PackageInfo) {
lexinfo := lexical.Structure(r.iprog.Fset, info.Pkg, &info.Info, info.Files)
b := lexinfo.Defs[from] // the block defining the 'from' object
if b != nil {
to, toBlock := b.Lookup(r.to)
if toBlock == b {
// same-block conflict
r.errorf(from.Pos(), "renaming this %s %q to %q",
objectKind(from), from.Name(), r.to)
r.errorf(to.Pos(), "\tconflicts with %s in same block",
objectKind(to))
return
} else if toBlock != nil {
// Check for super-block conflict.
// The name r.to is defined in a superblock.
// Is that name referenced from within this block?
for _, ref := range lexinfo.Refs[to] {
if obj, _ := ref.Env.Lookup(from.Name()); obj == from {
// super-block conflict
r.errorf(from.Pos(), "renaming this %s %q to %q",
objectKind(from), from.Name(), r.to)
r.errorf(ref.Id.Pos(), "\twould shadow this reference")
r.errorf(to.Pos(), "\tto the %s declared here",
objectKind(to))
return
}
}
}
}
// Check for sub-block conflict.
// Is there an intervening definition of r.to between
// the block defining 'from' and some reference to it?
for _, ref := range lexinfo.Refs[from] {
// TODO(adonovan): think about dot imports.
// (Is b == fromBlock an invariant?)
_, fromBlock := ref.Env.Lookup(from.Name())
fromDepth := fromBlock.Depth()
to, toBlock := ref.Env.Lookup(r.to)
if to != nil {
// sub-block conflict
if toBlock.Depth() > fromDepth {
r.errorf(from.Pos(), "renaming this %s %q to %q",
objectKind(from), from.Name(), r.to)
r.errorf(ref.Id.Pos(), "\twould cause this reference to become shadowed")
r.errorf(to.Pos(), "\tby this intervening %s definition",
objectKind(to))
return
}
}
}
// Renaming a type that is used as an embedded field
// requires renaming the field too. e.g.
// type T int // if we rename this to U..
// var s struct {T}
// print(s.T) // ...this must change too
if _, ok := from.(*types.TypeName); ok {
for id, obj := range info.Uses {
if obj == from {
if field := info.Defs[id]; field != nil {
r.check(field)
}
}
}
}
}
func (r *renamer) checkLabel(label *types.Label) {
// Check there are no identical labels in the function's label block.
// (Label blocks don't nest, so this is easy.)
if prev := label.Parent().Lookup(r.to); prev != nil {
r.errorf(label.Pos(), "renaming this label %q to %q", label.Name(), prev.Name())
r.errorf(prev.Pos(), "\twould conflict with this one")
}
}
// checkStructField checks that the field renaming will not cause
// conflicts at its declaration, or ambiguity or changes to any selection.
func (r *renamer) checkStructField(from *types.Var) {
// Check that the struct declaration is free of field conflicts,
// and field/method conflicts.
// go/types offers no easy way to get from a field (or interface
// method) to its declaring struct (or interface), so we must
// ascend the AST.
info, path, _ := r.iprog.PathEnclosingInterval(from.Pos(), from.Pos())
// path is [Ident Field FieldList StructType ... File]. Can't fail.
// Ascend past parens (unlikely).
i := 4
for {
_, ok := path[i].(*ast.ParenExpr)
if !ok {
break
}
i++
}
if spec, ok := path[i].(*ast.TypeSpec); ok {
// This struct is also a named type.
// We must check for direct (non-promoted) field/field
// and method/field conflicts.
named := info.Defs[spec.Name].Type()
prev, indices, _ := types.LookupFieldOrMethod(named, true, info.Pkg, r.to)
if len(indices) == 1 {
r.errorf(from.Pos(), "renaming this field %q to %q",
from.Name(), r.to)
r.errorf(prev.Pos(), "\twould conflict with this %s",
objectKind(prev))
return // skip checkSelections to avoid redundant errors
}
} else {
// This struct is not a named type.
// We need only check for direct (non-promoted) field/field conflicts.
T := info.Types[path[3].(*ast.StructType)].Type.Underlying().(*types.Struct)
for i := 0; i < T.NumFields(); i++ {
if prev := T.Field(i); prev.Name() == r.to {
r.errorf(from.Pos(), "renaming this field %q to %q",
from.Name(), r.to)
r.errorf(prev.Pos(), "\twould conflict with this field")
return // skip checkSelections to avoid redundant errors
}
}
}
// Renaming an anonymous field requires renaming the type too. e.g.
// print(s.T) // if we rename T to U,
// type T int // this and
// var s struct {T} // this must change too.
if from.Anonymous() {
if named, ok := from.Type().(*types.Named); ok {
r.check(named.Obj())
} else if named, ok := deref(from.Type()).(*types.Named); ok {
r.check(named.Obj())
}
}
// Check integrity of existing (field and method) selections.
r.checkSelections(from)
}
// checkSelection checks that all uses and selections that resolve to
// the specified object would continue to do so after the renaming.
func (r *renamer) checkSelections(from types.Object) {
for pkg, info := range r.packages {
if id := someUse(info, from); id != nil {
if !r.checkExport(id, pkg, from) {
return
}
}
for syntax, sel := range info.Selections {
// There may be extant selections of only the old
// name or only the new name, so we must check both.
// (If neither, the renaming is sound.)
//
// In both cases, we wish to compare the lengths
// of the implicit field path (Selection.Index)
// to see if the renaming would change it.
//
// If a selection that resolves to 'from', when renamed,
// would yield a path of the same or shorter length,
// this indicates ambiguity or a changed referent,
// analogous to same- or sub-block lexical conflict.
//
// If a selection using the name 'to' would
// yield a path of the same or shorter length,
// this indicates ambiguity or shadowing,
// analogous to same- or super-block lexical conflict.
// TODO(adonovan): fix: derive from Types[syntax.X].Mode
// TODO(adonovan): test with pointer, value, addressable value.
isAddressable := true
if sel.Obj() == from {
if obj, indices, _ := types.LookupFieldOrMethod(sel.Recv(), isAddressable, from.Pkg(), r.to); obj != nil {
// Renaming this existing selection of
// 'from' may block access to an existing
// type member named 'to'.
delta := len(indices) - len(sel.Index())
if delta > 0 {
continue // no ambiguity
}
r.selectionConflict(from, delta, syntax, obj)
return
}
} else if sel.Obj().Name() == r.to {
if obj, indices, _ := types.LookupFieldOrMethod(sel.Recv(), isAddressable, from.Pkg(), from.Name()); obj == from {
// Renaming 'from' may cause this existing
// selection of the name 'to' to change
// its meaning.
delta := len(indices) - len(sel.Index())
if delta > 0 {
continue // no ambiguity
}
r.selectionConflict(from, -delta, syntax, sel.Obj())
return
}
}
}
}
}
func (r *renamer) selectionConflict(from types.Object, delta int, syntax *ast.SelectorExpr, obj types.Object) {
r.errorf(from.Pos(), "renaming this %s %q to %q",
objectKind(from), from.Name(), r.to)
switch {
case delta < 0:
// analogous to sub-block conflict
r.errorf(syntax.Sel.Pos(),
"\twould change the referent of this selection")
r.errorf(obj.Pos(), "\tto this %s", objectKind(obj))
case delta == 0:
// analogous to same-block conflict
r.errorf(syntax.Sel.Pos(),
"\twould make this reference ambiguous")
r.errorf(obj.Pos(), "\twith this %s", objectKind(obj))
case delta > 0:
// analogous to super-block conflict
r.errorf(syntax.Sel.Pos(),
"\twould shadow this selection")
r.errorf(obj.Pos(), "\tto the %s declared here",
objectKind(obj))
}
}
// checkMethod performs safety checks for renaming a method.
// There are three hazards:
// - declaration conflicts
// - selection ambiguity/changes
// - entailed renamings of assignable concrete/interface types (for now, just reject)
func (r *renamer) checkMethod(from *types.Func) {
// e.g. error.Error
if from.Pkg() == nil {
r.errorf(from.Pos(), "you cannot rename built-in method %s", from)
return
}
// As always, having to support concrete methods with pointer
// and non-pointer receivers, and named vs unnamed types with
// methods, makes tooling fun.
// ASSIGNABILITY
//
// For now, if any method renaming breaks a required
// assignability to another type, we reject it.
//
// TODO(adonovan): probably we should compute the entailed
// renamings so that an interface method renaming causes
// concrete methods to change too. But which ones?
//
// There is no correct answer, only heuristics, because Go's
// "duck typing" doesn't distinguish intentional from contingent
// assignability. There are two obvious approaches:
//
// (1) Update the minimum set of types to preserve the
// assignability of types all syntactic assignments
// (incl. implicit ones in calls, returns, sends, etc).
// The satisfy.Finder enumerates these.
// This is likely to be an underapproximation.
//
// (2) Update all types that are assignable to/from the changed
// type. This requires computing the "implements" relation
// for all pairs of types (as godoc and oracle do).
// This is likely to be an overapproximation.
//
// If a concrete type is renamed, we probably do not want to
// rename corresponding interfaces; interface renamings should
// probably be initiated at the interface. (But what if a
// concrete type implements multiple interfaces with the same
// method? Then the user is stuck.)
//
// We need some experience before we decide how to implement this.
// Check for conflict at point of declaration.
// Check to ensure preservation of assignability requirements.
recv := from.Type().(*types.Signature).Recv().Type()
if isInterface(recv) {
// Abstract method
// declaration
prev, _, _ := types.LookupFieldOrMethod(recv, false, from.Pkg(), r.to)
if prev != nil {
r.errorf(from.Pos(), "renaming this interface method %q to %q",
from.Name(), r.to)
r.errorf(prev.Pos(), "\twould conflict with this method")
return
}
// Check all interfaces that embed this one for
// declaration conflicts too.
for _, info := range r.packages {
// Start with named interface types (better errors)
for _, obj := range info.Defs {
if obj, ok := obj.(*types.TypeName); ok && isInterface(obj.Type()) {
f, _, _ := types.LookupFieldOrMethod(
obj.Type(), false, from.Pkg(), from.Name())
if f == nil {
continue
}
t, _, _ := types.LookupFieldOrMethod(
obj.Type(), false, from.Pkg(), r.to)
if t == nil {
continue
}
r.errorf(from.Pos(), "renaming this interface method %q to %q",
from.Name(), r.to)
r.errorf(t.Pos(), "\twould conflict with this method")
r.errorf(obj.Pos(), "\tin named interface type %q", obj.Name())
}
}
// Now look at all literal interface types (includes named ones again).
for e, tv := range info.Types {
if e, ok := e.(*ast.InterfaceType); ok {
_ = e
_ = tv.Type.(*types.Interface)
// TODO(adonovan): implement same check as above.
}
}
}
// assignability
for T := range r.findAssignments(recv) {
if obj, _, _ := types.LookupFieldOrMethod(T, false, from.Pkg(), from.Name()); obj == nil {
continue
}
r.errorf(from.Pos(), "renaming this method %q to %q",
from.Name(), r.to)
var pos token.Pos
var other string
if named, ok := T.(*types.Named); ok {
pos = named.Obj().Pos()
other = named.Obj().Name()
} else {
pos = from.Pos()
other = T.String()
}
r.errorf(pos, "\twould make %s no longer assignable to it", other)
return
}
} else {
// Concrete method
// declaration
prev, indices, _ := types.LookupFieldOrMethod(recv, true, from.Pkg(), r.to)
if prev != nil && len(indices) == 1 {
r.errorf(from.Pos(), "renaming this method %q to %q",
from.Name(), r.to)
r.errorf(prev.Pos(), "\twould conflict with this %s",
objectKind(prev))
return
}
// assignability (of both T and *T)
recvBase := deref(recv)
for _, R := range []types.Type{recvBase, types.NewPointer(recvBase)} {
for I := range r.findAssignments(R) {
if obj, _, _ := types.LookupFieldOrMethod(I, true, from.Pkg(), from.Name()); obj == nil {
continue
}
r.errorf(from.Pos(), "renaming this method %q to %q",
from.Name(), r.to)
var pos token.Pos
var iface string
if named, ok := I.(*types.Named); ok {
pos = named.Obj().Pos()
iface = "interface " + named.Obj().Name()
} else {
pos = from.Pos()
iface = I.String()
}
r.errorf(pos, "\twould make it no longer assignable to %s", iface)
return // one is enough
}
}
}
// Check integrity of existing (field and method) selections.
// We skip this if there were errors above, to avoid redundant errors.
r.checkSelections(from)
}
func (r *renamer) checkExport(id *ast.Ident, pkg *types.Package, from types.Object) bool {
// Reject cross-package references if r.to is unexported.
// (Such references may be qualified identifiers or field/method
// selections.)
if !ast.IsExported(r.to) && pkg != from.Pkg() {
r.errorf(from.Pos(),
"renaming this %s %q to %q would make it unexported",
objectKind(from), from.Name(), r.to)
r.errorf(id.Pos(), "\tbreaking references from packages such as %q",
pkg.Path())
return false
}
return true
}
// findAssignments returns the set of types to or from which type T is
// assigned in the program syntax.
func (r *renamer) findAssignments(T types.Type) map[types.Type]bool {
if r.satisfyConstraints == nil {
// Compute on demand: it's expensive.
var f satisfy.Finder
for _, info := range r.packages {
f.Find(&info.Info, info.Files)
}
r.satisfyConstraints = f.Result
}
result := make(map[types.Type]bool)
for key := range r.satisfyConstraints {
// key = (lhs, rhs) where lhs is always an interface.
if types.Identical(key.RHS, T) {
result[key.LHS] = true
}
if isInterface(T) && types.Identical(key.LHS, T) {
// must check both sides
result[key.RHS] = true
}
}
return result
}
// -- helpers ----------------------------------------------------------
// someUse returns an arbitrary use of obj within info.
func someUse(info *loader.PackageInfo, obj types.Object) *ast.Ident {
for id, o := range info.Uses {
if o == obj {
return id
}
}
return nil
}
// -- Plundered from code.google.com/p/go.tools/go/ssa -----------------
func isInterface(T types.Type) bool {
_, ok := T.Underlying().(*types.Interface)
return ok
}
func deref(typ types.Type) types.Type {
if p, _ := typ.(*types.Pointer); p != nil {
return p.Elem()
}
return typ
}

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;;; Copyright 2014 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.
;;;
;;; Integration of the 'gorename' tool into Emacs.
;;;
;;; To install:
;;; % go get code.google.com/p/go.tools/cmd/gorename
;;; % go build code.google.com/p/go.tools/cmd/gorename
;;; % mv gorename $HOME/bin/ # or elsewhere on $PATH
;;;
;;; The go-rename-command variable can be customized to specify an
;;; alternative location for the installed command.
(require 'compile)
(require 'go-mode)
(require 'thingatpt)
(defgroup go-rename nil
"Options specific to the Go rename."
:group 'go)
(defcustom go-rename-command "gorename"
"The `gorename' command; by the default, $PATH is searched."
:type 'string
:group 'go-rename)
(defun go-rename (new-name)
"Rename the entity denoted by the identifier at point, using
the `gorename' tool."
(interactive (list (read-string "New name: " (thing-at-point 'symbol))))
(if (not buffer-file-name)
(error "Cannot use go-rename on a buffer without a file name"))
;; It's not sufficient to save the current buffer if modified,
;; since if gofmt-before-save is on the before-save-hook,
;; saving will disturb the selected region.
(if (buffer-modified-p)
(error "Please save the current buffer before invoking go-rename"))
;; Prompt-save all other modified Go buffers, since they might get written.
(save-some-buffers nil #'(lambda ()
(and (buffer-file-name)
(string= (file-name-extension (buffer-file-name)) ".go"))))
(let* ((posflag (format "-offset=%s:#%d"
buffer-file-name
(1- (go--position-bytes (point)))))
(env-vars (go-root-and-paths))
(goroot-env (concat "GOROOT=" (car env-vars)))
(gopath-env (concat "GOPATH=" (mapconcat #'identity (cdr env-vars) ":")))
success)
(with-current-buffer (get-buffer-create "*go-rename*")
(setq buffer-read-only nil)
(erase-buffer)
(let ((args (list go-rename-command nil t nil posflag "-to" new-name)))
;; Log the command to *Messages*, for debugging.
(message "Command: %s:" args)
(message "Running gorename...")
;; Use dynamic binding to modify/restore the environment
(setq success (zerop (let ((process-environment (list* goroot-env gopath-env process-environment)))
(apply #'call-process args))))
(insert "\n")
(compilation-mode)
(setq compilation-error-screen-columns nil)
;; On success, print the one-line result in the message bar,
;; and hide the *go-rename* buffer.
(let ((w (display-buffer (current-buffer))))
(if success
(progn
(message "%s" (go--buffer-string-no-trailing-space))
(delete-window w))
;; failure
(message "gorename exited")
(shrink-window-if-larger-than-buffer w)
(set-window-point w (point-min)))))))
;; Reload the modified files, saving line/col.
;; (Don't restore the point since the text has changed.)
;;
;; TODO(adonovan): should we also do this for all other files
;; that were updated (the tool can print them)?
(let ((line (line-number-at-pos))
(col (current-column)))
(revert-buffer t t t) ; safe, because we just saved it
(goto-char (point-min))
(forward-line (1- line))
(forward-char col)))
(defun go--buffer-string-no-trailing-space ()
(replace-regexp-in-string "[\t\n ]*\\'"
""
(buffer-substring (point-min) (point-max))))

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// Copyright 2014 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 rename contains the implementation of the 'gorename' command
// whose main function is in code.google.com/p/go.tools/refactor/rename.
// See that package for the command documentation.
package rename
import (
"errors"
"fmt"
"go/ast"
"go/build"
"go/format"
"go/parser"
"go/token"
"os"
"path/filepath"
"sort"
"strings"
"code.google.com/p/go.tools/go/loader"
"code.google.com/p/go.tools/go/types"
"code.google.com/p/go.tools/refactor/importgraph"
"code.google.com/p/go.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 bool
// DryRun causes the patch to be displayed but not applied.
DryRun bool
// ConfictError 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
)
type renamer struct {
iprog *loader.Program
objsToUpdate map[types.Object]bool
hadConflicts bool
to string
satisfyConstraints map[satisfy.Constraint]bool
packages map[*types.Package]*loader.PackageInfo // subset of iprog.AllPackages to inspect
}
var reportError = func(posn token.Position, message string) {
fmt.Fprintf(os.Stderr, "%s: %s\n", posn, message)
}
func Main(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)
}
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 {
fmt.Fprintln(os.Stderr, "Potentially global renaming; scanning workspace...")
}
// Scan the workspace and build the import graph.
_, rev, errors := importgraph.Build(ctxt)
if len(errors) > 0 {
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),
to: to,
packages: make(map[*types.Package]*loader.PackageInfo),
}
// 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
}
if DryRun {
// TODO(adonovan): print the delta?
return nil
}
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,
SourceImports: true,
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 {
fmt.Fprintf(os.Stderr, "Loading package: %s\n", pkg)
}
}
for pkg := range pkgs {
if err := conf.ImportWithTests(pkg); err != nil {
return nil, err
}
}
return conf.Load()
}
// 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)
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
}
}
for id, obj := range info.Uses {
if r.objsToUpdate[obj] {
nidents++
id.Name = r.to
filesToUpdate[r.iprog.Fset.File(id.Pos())] = true
}
}
}
// TODO(adonovan): don't rewrite cgo + generated 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 {
fmt.Fprintf(os.Stderr, "Updating package %s\n",
info.Pkg.Path())
}
}
if err := rewriteFile(r.iprog.Fset, f, tokenFile.Name(), tokenFile.Name()+".prename"); err != nil {
fmt.Fprintf(os.Stderr, "Error: %s.\n", err)
nerrs++
}
}
}
}
fmt.Fprintf(os.Stderr, "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
}
func plural(n int) string {
if n != 1 {
return "s"
}
return ""
}
var rewriteFile = func(fset *token.FileSet, f *ast.File, orig, backup string) (err error) {
// TODO(adonovan): print packages and filenames in a form useful
// to editors (so they can reload files).
if Verbose {
fmt.Fprintf(os.Stderr, "\t%s\n", orig)
}
if err := os.Rename(orig, backup); err != nil {
return fmt.Errorf("failed to make backup %s -> %s: %s",
orig, filepath.Base(backup), err)
}
out, err := os.Create(orig)
if err != nil {
// assume error includes the filename
return fmt.Errorf("failed to open file: %s", err)
}
defer func() {
if closeErr := out.Close(); err == nil {
err = closeErr // don't clobber existing error
}
}()
if err := format.Node(out, fset, f); err != nil {
return fmt.Errorf("failed to write file: %s", err)
}
return nil
}

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// Copyright 2014 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 rename
import (
"bytes"
"fmt"
"go/ast"
"go/build"
"go/format"
"go/token"
"io"
"io/ioutil"
"os"
"path/filepath"
"regexp"
"strconv"
"strings"
"testing"
"time"
)
// TODO(adonovan): test reported source positions, somehow.
func TestConflicts(t *testing.T) {
defer func(savedDryRun bool, savedReportError func(token.Position, string)) {
DryRun = savedDryRun
reportError = savedReportError
}(DryRun, reportError)
DryRun = true
var ctxt *build.Context
for _, test := range []struct {
ctxt *build.Context // nil => use previous
offset, from, to string // values of the -offset/-from and -to flags
want string // regexp to match conflict errors, or "OK"
}{
// init() checks
{
ctxt: fakeContext(map[string][]string{
"fmt": {`package fmt; type Stringer interface { String() }`},
"main": {`
package main
import foo "fmt"
var v foo.Stringer
func f() { v.String(); f() }
`,
`package main; var w int`},
}),
from: "main.v", to: "init",
want: `you cannot have a var at package level named "init"`,
},
{
from: "main.f", to: "init",
want: `renaming this func "f" to "init" would make it a package initializer.*` +
`but references to it exist`,
},
{
from: "/go/src/main/0.go::foo", to: "init",
want: `"init" is not a valid imported package name`,
},
// Export checks
{
from: "fmt.Stringer", to: "stringer",
want: `renaming this type "Stringer" to "stringer" would make it unexported.*` +
`breaking references from packages such as "main"`,
},
{
from: "(fmt.Stringer).String", to: "string",
want: `renaming this method "String" to "string" would make it unexported.*` +
`breaking references from packages such as "main"`,
},
// Lexical scope checks
{
// file/package conflict, same file
from: "main.v", to: "foo",
want: `renaming this var "v" to "foo" would conflict.*` +
`with this imported package name`,
},
{
// file/package conflict, same file
from: "main::foo", to: "v",
want: `renaming this imported package name "foo" to "v" would conflict.*` +
`with this package member var`,
},
{
// file/package conflict, different files
from: "main.w", to: "foo",
want: `renaming this var "w" to "foo" would conflict.*` +
`with this imported package name`,
},
{
// file/package conflict, different files
from: "main::foo", to: "w",
want: `renaming this imported package name "foo" to "w" would conflict.*` +
`with this package member var`,
},
{
ctxt: main(`
package main
var x, z int
func f(y int) {
print(x)
print(y)
}
func g(w int) {
print(x)
x := 1
print(x)
}`),
from: "main.x", to: "y",
want: `renaming this var "x" to "y".*` +
`would cause this reference to become shadowed.*` +
`by this intervening var definition`,
},
{
from: "main.g::x", to: "w",
want: `renaming this var "x" to "w".*` +
`conflicts with var in same block`,
},
{
from: "main.f::y", to: "x",
want: `renaming this var "y" to "x".*` +
`would shadow this reference.*` +
`to the var declared here`,
},
{
from: "main.g::w", to: "x",
want: `renaming this var "w" to "x".*` +
`conflicts with var in same block`,
},
{
from: "main.z", to: "y", want: "OK",
},
// Label checks
{
ctxt: main(`
package main
func f() {
foo:
goto foo
bar:
goto bar
func(x int) {
wiz:
goto wiz
}(0)
}
`),
from: "main.f::foo", to: "bar",
want: `renaming this label "foo" to "bar".*` +
`would conflict with this one`,
},
{
from: "main.f::foo", to: "wiz", want: "OK",
},
{
from: "main.f::wiz", to: "x", want: "OK",
},
{
from: "main.f::x", to: "wiz", want: "OK",
},
{
from: "main.f::wiz", to: "foo", want: "OK",
},
// Struct fields
{
ctxt: main(`
package main
type U struct { u int }
type V struct { v int }
func (V) x() {}
type W (struct {
U
V
w int
})
func f() {
var w W
print(w.u) // NB: there is no selection of w.v
var _ struct { yy, zz int }
}
`),
// field/field conflict in named struct declaration
from: "(main.W).U", to: "w",
want: `renaming this field "U" to "w".*` +
`would conflict with this field`,
},
{
// rename type used as embedded field
// => rename field
// => field/field conflict
// This is an entailed renaming;
// it would be nice if we checked source positions.
from: "main.U", to: "w",
want: `renaming this field "U" to "w".*` +
`would conflict with this field`,
},
{
// field/field conflict in unnamed struct declaration
from: "main.f::zz", to: "yy",
want: `renaming this field "zz" to "yy".*` +
`would conflict with this field`,
},
// Now we test both directions of (u,v) (u,w) (v,w) (u,x) (v,x).
// Too bad we don't test position info...
{
// field/field ambiguity at same promotion level ('from' selection)
from: "(main.U).u", to: "v",
want: `renaming this field "u" to "v".*` +
`would make this reference ambiguous.*` +
`with this field`,
},
{
// field/field ambiguity at same promotion level ('to' selection)
from: "(main.V).v", to: "u",
want: `renaming this field "v" to "u".*` +
`would make this reference ambiguous.*` +
`with this field`,
},
{
// field/method conflict at different promotion level ('from' selection)
from: "(main.U).u", to: "w",
want: `renaming this field "u" to "w".*` +
`would change the referent of this selection.*` +
`to this field`,
},
{
// field/field shadowing at different promotion levels ('to' selection)
from: "(main.W).w", to: "u",
want: `renaming this field "w" to "u".*` +
`would shadow this selection.*` +
`to the field declared here`,
},
{
from: "(main.V).v", to: "w",
want: "OK", // since no selections are made ambiguous
},
{
from: "(main.W).w", to: "v",
want: "OK", // since no selections are made ambiguous
},
{
// field/method ambiguity at same promotion level ('from' selection)
from: "(main.U).u", to: "x",
want: `renaming this field "u" to "x".*` +
`would make this reference ambiguous.*` +
`with this method`,
},
{
// field/field ambiguity at same promotion level ('to' selection)
from: "(main.V).x", to: "u",
want: `renaming this method "x" to "u".*` +
`would make this reference ambiguous.*` +
`with this field`,
},
{
// field/method conflict at named struct declaration
from: "(main.V).v", to: "x",
want: `renaming this field "v" to "x".*` +
`would conflict with this method`,
},
{
// field/method conflict at named struct declaration
from: "(main.V).x", to: "v",
want: `renaming this method "x" to "v".*` +
`would conflict with this field`,
},
// Methods
{
ctxt: main(`
package main
type C int
func (C) f()
func (C) g()
type D int
func (*D) f()
func (*D) g()
type I interface { f(); g() }
type J interface { I; h() }
var _ I = new(D)
var _ interface {f()} = C(0)
`),
from: "(main.I).f", to: "g",
want: `renaming this interface method "f" to "g".*` +
`would conflict with this method`,
},
{
from: "(main.I).f", to: "h",
want: `renaming this interface method "f" to "h".*` +
`would conflict with this method.*` +
`in named interface type "J"`,
},
{
// type J interface { h; h() } is not a conflict, amusingly.
from: "main.I", to: "h",
want: `OK`,
},
{
from: "(main.J).h", to: "f",
want: `renaming this interface method "h" to "f".*` +
`would conflict with this method`,
},
{
from: "(main.C).f", to: "e",
want: `renaming this method "f" to "e".*` +
`would make it no longer assignable to interface{f..}`,
},
{
from: "(main.D).g", to: "e",
want: `renaming this method "g" to "e".*` +
`would make it no longer assignable to interface I`,
},
{
from: "(main.I).f", to: "e",
want: `renaming this method "f" to "e".*` +
`would make \*main.D no longer assignable to it`,
},
} {
var conflicts []string
reportError = func(posn token.Position, message string) {
conflicts = append(conflicts, message)
}
if test.ctxt != nil {
ctxt = test.ctxt
}
err := Main(ctxt, test.offset, test.from, test.to)
var prefix string
if test.offset == "" {
prefix = fmt.Sprintf("-from %q -to %q", test.from, test.to)
} else {
prefix = fmt.Sprintf("-offset %q -to %q", test.offset, test.to)
}
if err == ConflictError {
got := strings.Join(conflicts, "\n")
if false {
t.Logf("%s: %s", prefix, got)
}
pattern := "(?s:" + test.want + ")" // enable multi-line matching
if !regexp.MustCompile(pattern).MatchString(got) {
t.Errorf("%s: conflict does not match pattern:\n"+
"Conflict:\t%s\n"+
"Pattern: %s",
prefix, got, test.want)
}
} else if err != nil {
t.Errorf("%s: unexpected error: %s", prefix, err)
} else if test.want != "OK" {
t.Errorf("%s: unexpected success, want conflicts matching:\n%s",
prefix, test.want)
}
}
}
func TestRewrites(t *testing.T) {
defer func(savedRewriteFile func(*token.FileSet, *ast.File, string, string) error) {
rewriteFile = savedRewriteFile
}(rewriteFile)
var ctxt *build.Context
for _, test := range []struct {
ctxt *build.Context // nil => use previous
offset, from, to string // values of the -from/-offset and -to flags
want map[string]string // contents of updated files
}{
// Elimination of renaming import.
{
ctxt: fakeContext(map[string][]string{
"foo": {`package foo; type T int`},
"main": {`package main
import foo2 "foo"
var _ foo2.T
`},
}),
from: "main::foo2", to: "foo",
want: map[string]string{
"/go/src/main/0.go": `package main
import "foo"
var _ foo.T
`,
},
},
// Introduction of renaming import.
{
ctxt: fakeContext(map[string][]string{
"foo": {`package foo; type T int`},
"main": {`package main
import "foo"
var _ foo.T
`},
}),
offset: "/go/src/main/0.go:#36", to: "foo2", // the "foo" in foo.T
want: map[string]string{
"/go/src/main/0.go": `package main
import foo2 "foo"
var _ foo2.T
`,
},
},
// Renaming of package-level member.
{
from: "foo.T", to: "U",
want: map[string]string{
"/go/src/main/0.go": `package main
import "foo"
var _ foo.U
`,
"/go/src/foo/0.go": `package foo
type U int
`,
},
},
// Label renamings.
{
ctxt: main(`package main
func f() {
loop:
loop := 0
go func() {
loop:
goto loop
}()
loop++
goto loop
}
`),
offset: "/go/src/main/0.go:#25", to: "loop2", // def of outer label "loop"
want: map[string]string{
"/go/src/main/0.go": `package main
func f() {
loop2:
loop := 0
go func() {
loop:
goto loop
}()
loop++
goto loop2
}
`,
},
},
{
offset: "/go/src/main/0.go:#70", to: "loop2", // ref to inner label "loop"
want: map[string]string{
"/go/src/main/0.go": `package main
func f() {
loop:
loop := 0
go func() {
loop2:
goto loop2
}()
loop++
goto loop
}
`,
},
},
// Renaming of type used as embedded field.
{
ctxt: main(`package main
type T int
type U struct { T }
var _ = U{}.T
`),
from: "main.T", to: "T2",
want: map[string]string{
"/go/src/main/0.go": `package main
type T2 int
type U struct{ T2 }
var _ = U{}.T2
`,
},
},
// Renaming of embedded field.
{
ctxt: main(`package main
type T int
type U struct { T }
var _ = U{}.T
`),
offset: "/go/src/main/0.go:#58", to: "T2", // T in "U{}.T"
want: map[string]string{
"/go/src/main/0.go": `package main
type T2 int
type U struct{ T2 }
var _ = U{}.T2
`,
},
},
// Renaming of pointer embedded field.
{
ctxt: main(`package main
type T int
type U struct { *T }
var _ = U{}.T
`),
offset: "/go/src/main/0.go:#59", to: "T2", // T in "U{}.T"
want: map[string]string{
"/go/src/main/0.go": `package main
type T2 int
type U struct{ *T2 }
var _ = U{}.T2
`,
},
},
// Lexical scope tests.
{
ctxt: main(`package main
var y int
func f() {
print(y)
y := ""
print(y)
}
`),
from: "main.y", to: "x",
want: map[string]string{
"/go/src/main/0.go": `package main
var x int
func f() {
print(x)
y := ""
print(y)
}
`,
},
},
{
from: "main.f::y", to: "x",
want: map[string]string{
"/go/src/main/0.go": `package main
var y int
func f() {
print(y)
x := ""
print(x)
}
`,
},
},
// Renaming of typeswitch vars (a corner case).
{
ctxt: main(`package main
func f(z interface{}) {
switch y := z.(type) {
case int:
print(y)
default:
print(y)
}
}
`),
offset: "/go/src/main/0.go:#46", to: "x", // def of y
want: map[string]string{
"/go/src/main/0.go": `package main
func f(z interface{}) {
switch x := z.(type) {
case int:
print(x)
default:
print(x)
}
}
`},
},
{
offset: "/go/src/main/0.go:#81", to: "x", // ref of y in case int
want: map[string]string{
"/go/src/main/0.go": `package main
func f(z interface{}) {
switch x := z.(type) {
case int:
print(x)
default:
print(x)
}
}
`},
},
{
offset: "/go/src/main/0.go:#102", to: "x", // ref of y in default case
want: map[string]string{
"/go/src/main/0.go": `package main
func f(z interface{}) {
switch x := z.(type) {
case int:
print(x)
default:
print(x)
}
}
`},
},
} {
if test.ctxt != nil {
ctxt = test.ctxt
}
got := make(map[string]string)
rewriteFile = func(fset *token.FileSet, f *ast.File, orig, backup string) error {
var out bytes.Buffer
if err := format.Node(&out, fset, f); err != nil {
return err
}
got[orig] = out.String()
return nil
}
err := Main(ctxt, test.offset, test.from, test.to)
var prefix string
if test.offset == "" {
prefix = fmt.Sprintf("-from %q -to %q", test.from, test.to)
} else {
prefix = fmt.Sprintf("-offset %q -to %q", test.offset, test.to)
}
if err != nil {
t.Errorf("%s: unexpected error: %s", prefix, err)
continue
}
for file, wantContent := range test.want {
gotContent, ok := got[file]
delete(got, file)
if !ok {
t.Errorf("%s: file %s not rewritten", prefix, file)
continue
}
if gotContent != wantContent {
t.Errorf("%s: rewritten file %s does not match expectation; got <<<%s>>>\n"+
"want <<<%s>>>", prefix, file, gotContent, wantContent)
}
}
// got should now be empty
for file := range got {
t.Errorf("%s: unexpected rewrite of file %s", prefix, file)
}
}
}
// ---------------------------------------------------------------------
// Plundered/adapted from go/loader/loader_test.go
// TODO(adonovan): make this into a nice testing utility within go/buildutil.
// pkgs maps the import path of a fake package to a list of its file contents;
// file names are synthesized, e.g. %d.go.
func fakeContext(pkgs map[string][]string) *build.Context {
ctxt := build.Default // copy
ctxt.GOROOT = "/go"
ctxt.GOPATH = ""
ctxt.IsDir = func(path string) bool {
if path == "/go/src" {
return true // needed by (*build.Context).SrcDirs
}
if p := strings.TrimPrefix(path, "/go/src/"); p == path {
return false
} else {
path = p
}
_, ok := pkgs[path]
return ok
}
ctxt.ReadDir = func(dir string) ([]os.FileInfo, error) {
dir = dir[len("/go/src/"):]
var fis []os.FileInfo
if dir == "" {
// Assumes keys of pkgs are single-segment.
for p := range pkgs {
fis = append(fis, fakeDirInfo(p))
}
} else {
for i := range pkgs[dir] {
fis = append(fis, fakeFileInfo(i))
}
}
return fis, nil
}
ctxt.OpenFile = func(path string) (io.ReadCloser, error) {
path = path[len("/go/src/"):]
dir, base := filepath.Split(path)
dir = filepath.Clean(dir)
index, _ := strconv.Atoi(strings.TrimSuffix(base, ".go"))
return ioutil.NopCloser(bytes.NewBufferString(pkgs[dir][index])), nil
}
return &ctxt
}
// helper for single-file main packages with no imports.
func main(content string) *build.Context {
return fakeContext(map[string][]string{"main": {content}})
}
type fakeFileInfo int
func (fi fakeFileInfo) Name() string { return fmt.Sprintf("%d.go", fi) }
func (fakeFileInfo) Sys() interface{} { return nil }
func (fakeFileInfo) ModTime() time.Time { return time.Time{} }
func (fakeFileInfo) IsDir() bool { return false }
func (fakeFileInfo) Size() int64 { return 0 }
func (fakeFileInfo) Mode() os.FileMode { return 0644 }
type fakeDirInfo string
func (fd fakeDirInfo) Name() string { return string(fd) }
func (fakeDirInfo) Sys() interface{} { return nil }
func (fakeDirInfo) ModTime() time.Time { return time.Time{} }
func (fakeDirInfo) IsDir() bool { return true }
func (fakeDirInfo) Size() int64 { return 0 }
func (fakeDirInfo) Mode() os.FileMode { return 0755 }

532
refactor/rename/spec.go Normal file
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@ -0,0 +1,532 @@
// Copyright 2014 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 rename
// This file contains logic related to specifying a renaming: parsing of
// the flags as a form of query, and finding the object(s) it denotes.
// See FromFlagUsage for details.
import (
"bytes"
"fmt"
"go/ast"
"go/build"
"go/parser"
"go/token"
"os"
"path/filepath"
"strconv"
"strings"
"code.google.com/p/go.tools/go/buildutil"
"code.google.com/p/go.tools/go/loader"
"code.google.com/p/go.tools/go/types"
)
// A spec specifies an entity to rename.
//
// It is populated from an -offset flag or -from query; see
// FromFlagUsage for the allowed -from query forms.
//
type spec struct {
// pkg is the package containing the position
// specified by the -from or -offset flag.
// If filename == "", our search for the 'from' entity
// is restricted to this package.
pkg string
// The original name of the entity being renamed.
// If the query had a ::from component, this is that;
// otherwise it's the last segment, e.g.
// (encoding/json.Decoder).from
// encoding/json.from
fromName string
// -- The remaining fields are private to this file. All are optional. --
// The query's ::x suffix, if any.
searchFor string
// e.g. "Decoder" in "(encoding/json.Decoder).fieldOrMethod"
// or "encoding/json.Decoder
pkgMember string
// e.g. fieldOrMethod in "(encoding/json.Decoder).fieldOrMethod"
typeMember string
// Restricts the query to this file.
// Implied by -from="file.go::x" and -offset flags.
filename string
// Byte offset of the 'from' identifier within the file named 'filename'.
// -offset mode only.
offset int
}
const FromFlagUsage = `
A legal -from query has one of the following forms:
(encoding/json.Decoder).Decode method of package-level named type
(encoding/json.Decoder).buf field of package-level named struct type
encoding/json.HTMLEscape package member (const, func, var, type)
(encoding/json.Decoder).Decode::x local object x within a method
encoding/json.HTMLEscape::x local object x within a function
encoding/json::x object x anywhere within a package
json.go::x object x within file json.go
For methods attached to a pointer type, the '*' must not be specified.
[TODO(adonovan): fix that.]
It is an error if one of the ::x queries matches multiple objects.
`
// parseFromFlag interprets the "-from" flag value as a renaming specification.
// See FromFlagUsage for valid formats.
func parseFromFlag(ctxt *build.Context, fromFlag string) (*spec, error) {
var spec spec
var main string // sans "::x" suffix
switch parts := strings.Split(fromFlag, "::"); len(parts) {
case 1:
main = parts[0]
case 2:
main = parts[0]
spec.searchFor = parts[1]
if parts[1] == "" {
// error
}
default:
return nil, fmt.Errorf("-from %q: invalid identifier specification (see -help for formats)", fromFlag)
}
// main is one of:
// filename.go
// importpath
// importpath.member
// (importpath.type).fieldormethod
if strings.HasSuffix(main, ".go") {
// filename.go
if spec.searchFor == "" {
return nil, fmt.Errorf("-from: filename %q must have a ::name suffix", main)
}
spec.filename = main
if !buildutil.FileExists(ctxt, spec.filename) {
return nil, fmt.Errorf("no such file: %s", spec.filename)
}
// Guess the default package.
var err error
if spec.pkg, err = guessImportPath(spec.filename, ctxt); err != nil {
return nil, fmt.Errorf("-from: couldn't guess package from filename: %s: %s",
spec.filename, err)
}
} else if a, b := splitAtLastDot(main); b == "" {
// importpath e.g. "encoding/json"
if spec.searchFor == "" {
return nil, fmt.Errorf("-from %q: package import path %q must have a ::name suffix",
main, a)
}
spec.pkg = a
} else if strings.HasPrefix(a, "(") && strings.HasSuffix(a, ")") {
// field/method of type e.g. (encoding/json.Decoder).Decode
c, d := splitAtLastDot(a[1 : len(a)-1])
if d == "" {
return nil, fmt.Errorf("-from %q: not a package-level named type: %q", a)
}
spec.pkg = c // e.g. "encoding/json"
spec.pkgMember = d // e.g. "Decoder"
spec.typeMember = b // e.g. "Decode"
spec.fromName = b
} else {
// package member e.g. "encoding/json.HTMLEscape"
spec.pkg = a // e.g. "encoding/json"
spec.pkgMember = b // e.g. "HTMLEscape"
spec.fromName = b
}
if spec.searchFor != "" {
spec.fromName = spec.searchFor
}
// Sanitize the package.
// TODO(adonovan): test with relative packages. May need loader changes.
bp, err := ctxt.Import(spec.pkg, ".", build.FindOnly)
if err != nil {
return nil, fmt.Errorf("can't find package %q", spec.pkg)
}
spec.pkg = bp.ImportPath
if !isValidIdentifier(spec.fromName) {
return nil, fmt.Errorf("-from: invalid identifier %q", spec.fromName)
}
if Verbose {
fmt.Fprintf(os.Stderr, "-from spec: %+v\n", spec)
}
return &spec, nil
}
// "encoding/json.HTMLEscape" -> ("encoding/json", "HTMLEscape")
// "encoding/json" -> ("encoding/json", "")
func splitAtLastDot(s string) (string, string) {
i := strings.LastIndex(s, ".")
if i == -1 {
return s, ""
}
return s[:i], s[i+1:]
}
// parseOffsetFlag interprets the "-offset" flag value as a renaming specification.
func parseOffsetFlag(ctxt *build.Context, offsetFlag string) (*spec, error) {
var spec spec
// Validate -offset, e.g. file.go:#123
parts := strings.Split(offsetFlag, ":#")
if len(parts) != 2 {
return nil, fmt.Errorf("-offset %q: invalid offset specification", offsetFlag)
}
spec.filename = parts[0]
if !buildutil.FileExists(ctxt, spec.filename) {
return nil, fmt.Errorf("no such file: %s", spec.filename)
}
// Guess the default package.
var err error
if spec.pkg, err = guessImportPath(spec.filename, ctxt); err != nil {
return nil, fmt.Errorf("couldn't guess package from filename: %s: %s",
spec.filename, err)
}
for _, r := range parts[1] {
if !isDigit(r) {
return nil, fmt.Errorf("-offset %q: non-numeric offset", offsetFlag)
}
}
spec.offset, err = strconv.Atoi(parts[1])
if err != nil {
return nil, fmt.Errorf("-offset %q: non-numeric offset", offsetFlag)
}
// Parse the file and check there's an identifier at that offset.
fset := token.NewFileSet()
f, err := buildutil.ParseFile(fset, ctxt, nil, wd, spec.filename, parser.ParseComments)
if err != nil {
return nil, fmt.Errorf("-offset %q: cannot parse file: %s", offsetFlag, err)
}
id := identAtOffset(fset, f, spec.offset)
if id == nil {
return nil, fmt.Errorf("-offset %q: no identifier at this position", offsetFlag)
}
spec.fromName = id.Name
return &spec, nil
}
var wd = func() string {
wd, err := os.Getwd()
if err != nil {
panic("cannot get working directory: " + err.Error())
}
return wd
}()
// For source trees built with 'go build', the -from or -offset
// spec identifies exactly one initial 'from' object to rename ,
// but certain proprietary build systems allow a single file to
// appear in multiple packages (e.g. the test package contains a
// copy of its library), so there may be multiple objects for
// the same source entity.
func findFromObjects(iprog *loader.Program, spec *spec) ([]types.Object, error) {
if spec.filename != "" {
return findFromObjectsInFile(iprog, spec)
}
// Search for objects defined in specified package.
// TODO(adonovan): the iprog.ImportMap has an entry {"main": ...}
// for main packages, even though that's not an import path.
// Seems like a bug.
//
// pkgObj := iprog.ImportMap[spec.pkg]
// if pkgObj == nil {
// return fmt.Errorf("cannot find package %s", spec.pkg) // can't happen?
// }
// Workaround: lookup by value.
var pkgObj *types.Package
for pkg := range iprog.AllPackages {
if pkg.Path() == spec.pkg {
pkgObj = pkg
break
}
}
info := iprog.AllPackages[pkgObj]
objects, err := findObjects(info, spec)
if err != nil {
return nil, err
}
if len(objects) > 1 {
// ambiguous "*" scope query
return nil, ambiguityError(iprog.Fset, objects)
}
return objects, nil
}
func findFromObjectsInFile(iprog *loader.Program, spec *spec) ([]types.Object, error) {
var fromObjects []types.Object
for _, info := range iprog.AllPackages {
// restrict to specified filename
// NB: under certain proprietary build systems, a given
// filename may appear in multiple packages.
for _, f := range info.Files {
thisFile := iprog.Fset.File(f.Pos())
if !sameFile(thisFile.Name(), spec.filename) {
continue
}
// This package contains the query file.
if spec.offset != 0 {
// Search for a specific ident by file/offset.
id := identAtOffset(iprog.Fset, f, spec.offset)
if id == nil {
// can't happen?
return nil, fmt.Errorf("identifier not found")
}
obj := info.Uses[id]
if obj == nil {
obj = info.Defs[id]
if obj == nil {
// Ident without Object.
// Package clause?
pos := thisFile.Pos(spec.offset)
_, path, _ := iprog.PathEnclosingInterval(pos, pos)
if len(path) == 2 { // [Ident File]
// TODO(adonovan): support this case.
return nil, fmt.Errorf("cannot rename %q: renaming package clauses is not yet supported",
path[1].(*ast.File).Name.Name)
}
// Implicit y in "switch y := x.(type) {"?
if obj := typeSwitchVar(&info.Info, path); obj != nil {
return []types.Object{obj}, nil
}
// Probably a type error.
return nil, fmt.Errorf("cannot find object for %q", id.Name)
}
}
if obj.Pkg() == nil {
return nil, fmt.Errorf("cannot rename predeclared identifiers (%s)", obj)
}
fromObjects = append(fromObjects, obj)
} else {
// do a package-wide query
objects, err := findObjects(info, spec)
if err != nil {
return nil, err
}
// filter results: only objects defined in thisFile
var filtered []types.Object
for _, obj := range objects {
if iprog.Fset.File(obj.Pos()) == thisFile {
filtered = append(filtered, obj)
}
}
if len(filtered) == 0 {
return nil, fmt.Errorf("no object %q declared in file %s",
spec.fromName, spec.filename)
} else if len(filtered) > 1 {
return nil, ambiguityError(iprog.Fset, filtered)
}
fromObjects = append(fromObjects, filtered[0])
}
break
}
}
if len(fromObjects) == 0 {
// can't happen?
return nil, fmt.Errorf("file %s was not part of the loaded program", spec.filename)
}
return fromObjects, nil
}
func typeSwitchVar(info *types.Info, path []ast.Node) types.Object {
if len(path) > 3 {
// [Ident AssignStmt TypeSwitchStmt...]
if sw, ok := path[2].(*ast.TypeSwitchStmt); ok {
// choose the first case.
if len(sw.Body.List) > 0 {
obj := info.Implicits[sw.Body.List[0].(*ast.CaseClause)]
if obj != nil {
return obj
}
}
}
}
return nil
}
// On success, findObjects returns the list of objects named
// spec.fromName matching the spec. On success, the result has exactly
// one element unless spec.searchFor!="", in which case it has at least one
// element.
//
func findObjects(info *loader.PackageInfo, spec *spec) ([]types.Object, error) {
if spec.pkgMember == "" {
if spec.searchFor == "" {
panic(spec)
}
objects := searchDefs(&info.Info, spec.searchFor)
if objects == nil {
return nil, fmt.Errorf("no object %q declared in package %q",
spec.searchFor, info.Pkg.Path())
}
return objects, nil
}
pkgMember := info.Pkg.Scope().Lookup(spec.pkgMember)
if pkgMember == nil {
return nil, fmt.Errorf("package %q has no member %q",
info.Pkg.Path(), spec.pkgMember)
}
var searchFunc *types.Func
if spec.typeMember == "" {
// package member
if spec.searchFor == "" {
return []types.Object{pkgMember}, nil
}
// Search within pkgMember, which must be a function.
searchFunc, _ = pkgMember.(*types.Func)
if searchFunc == nil {
return nil, fmt.Errorf("cannot search for %q within %s %q",
spec.searchFor, objectKind(pkgMember), pkgMember)
}
} else {
// field/method of type
// e.g. (encoding/json.Decoder).Decode
// or ::x within it.
tName, _ := pkgMember.(*types.TypeName)
if tName == nil {
return nil, fmt.Errorf("%s.%s is a %s, not a type",
info.Pkg.Path(), pkgMember.Name(), objectKind(pkgMember))
}
// search within named type.
obj, _, _ := types.LookupFieldOrMethod(tName.Type(), true, info.Pkg, spec.typeMember)
if obj == nil {
return nil, fmt.Errorf("cannot find field or method %q of %s %s.%s",
spec.typeMember, typeKind(tName.Type()), info.Pkg.Path(), tName.Name())
}
if spec.searchFor == "" {
return []types.Object{obj}, nil
}
searchFunc, _ = obj.(*types.Func)
if searchFunc == nil {
return nil, fmt.Errorf("cannot search for local name %q within %s (%s.%s).%s; need a function",
spec.searchFor, objectKind(obj), info.Pkg.Path(), tName.Name(),
obj.Name())
}
if isInterface(tName.Type()) {
return nil, fmt.Errorf("cannot search for local name %q within abstract method (%s.%s).%s",
spec.searchFor, info.Pkg.Path(), tName.Name(), searchFunc.Name())
}
}
// -- search within function or method --
decl := funcDecl(info, searchFunc)
if decl == nil {
return nil, fmt.Errorf("cannot find syntax for %s", searchFunc) // can't happen?
}
var objects []types.Object
for _, obj := range searchDefs(&info.Info, spec.searchFor) {
// We use positions, not scopes, to determine whether
// the obj is within searchFunc. This is clumsy, but the
// alternative, using the types.Scope tree, doesn't
// account for non-lexical objects like fields and
// interface methods.
if decl.Pos() <= obj.Pos() && obj.Pos() < decl.End() && obj != searchFunc {
objects = append(objects, obj)
}
}
if objects == nil {
return nil, fmt.Errorf("no local definition of %q within %s",
spec.searchFor, searchFunc)
}
return objects, nil
}
func funcDecl(info *loader.PackageInfo, fn *types.Func) *ast.FuncDecl {
for _, f := range info.Files {
for _, d := range f.Decls {
if d, ok := d.(*ast.FuncDecl); ok && info.Defs[d.Name] == fn {
return d
}
}
}
return nil
}
func searchDefs(info *types.Info, name string) []types.Object {
var objects []types.Object
for id, obj := range info.Defs {
if obj == nil {
// e.g. blank ident.
// TODO(adonovan): but also implicit y in
// switch y := x.(type)
// Needs some thought.
continue
}
if id.Name == name {
objects = append(objects, obj)
}
}
return objects
}
func identAtOffset(fset *token.FileSet, f *ast.File, offset int) *ast.Ident {
var found *ast.Ident
ast.Inspect(f, func(n ast.Node) bool {
if id, ok := n.(*ast.Ident); ok {
idpos := fset.Position(id.Pos()).Offset
if idpos <= offset && offset < idpos+len(id.Name) {
found = id
}
}
return found == nil // keep traversing only until found
})
return found
}
// ambiguityError returns an error describing an ambiguous "*" scope query.
func ambiguityError(fset *token.FileSet, objects []types.Object) error {
var buf bytes.Buffer
for i, obj := range objects {
if i > 0 {
buf.WriteString(", ")
}
posn := fset.Position(obj.Pos())
fmt.Fprintf(&buf, "%s at %s:%d",
objectKind(obj), filepath.Base(posn.Filename), posn.Column)
}
return fmt.Errorf("ambiguous specifier %s matches %s",
objects[0].Name(), buf.String())
}

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refactor/rename/util.go Normal file
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// Copyright 2014 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 rename
import (
"fmt"
"go/build"
"os"
"path/filepath"
"reflect"
"strings"
"unicode"
"code.google.com/p/go.tools/go/types"
)
func objectKind(obj types.Object) string {
switch obj := obj.(type) {
case *types.PkgName:
return "imported package name"
case *types.TypeName:
return "type"
case *types.Var:
if obj.IsField() {
return "field"
}
case *types.Func:
if obj.Type().(*types.Signature).Recv() != nil {
return "method"
}
}
// label, func, var, const
return strings.ToLower(strings.TrimPrefix(reflect.TypeOf(obj).String(), "*types."))
}
func typeKind(T types.Type) string {
return strings.ToLower(strings.TrimPrefix(reflect.TypeOf(T.Underlying()).String(), "*types."))
}
// NB: for renamings, blank is not considered valid.
func isValidIdentifier(id string) bool {
if id == "" || id == "_" {
return false
}
for i, r := range id {
if !isLetter(r) && (i == 0 || !isDigit(r)) {
return false
}
}
return true
}
// isLocal reports whether obj is local to some function.
// Precondition: not a struct field or interface method.
func isLocal(obj types.Object) bool {
// [... 5=stmt 4=func 3=file 2=pkg 1=universe]
var depth int
for scope := obj.Parent(); scope != nil; scope = scope.Parent() {
depth++
}
return depth >= 4
}
func isPackageLevel(obj types.Object) bool {
return obj.Pkg().Scope().Lookup(obj.Name()) == obj
}
// -- Plundered from go/scanner: ---------------------------------------
func isLetter(ch rune) bool {
return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch == '_' || ch >= 0x80 && unicode.IsLetter(ch)
}
func isDigit(ch rune) bool {
return '0' <= ch && ch <= '9' || ch >= 0x80 && unicode.IsDigit(ch)
}
// -- Plundered from code.google.com/p/go.tools/oracle -----------------
// guessImportPath finds the package containing filename, and returns
// its import path relative to it.
func guessImportPath(filename string, ctxt *build.Context) (importPath string, err error) {
// TODO(adonovan): move this to package "buildutil"; factor in common with oracle.
// bp, err := buildutil.ContainingPackage(ctxt, wd, filename)
// if err != nil {
// return
// }
// return bp.ImportPath, nil
absFile, err := filepath.Abs(filename)
if err != nil {
err = fmt.Errorf("can't form absolute path of %s", filename)
return
}
absFileDir := segments(filepath.Dir(absFile))
// Find the innermost directory in $GOPATH that encloses filename.
minD := 1024
for _, gopathDir := range ctxt.SrcDirs() {
// We can assume $GOPATH and $GOROOT dirs are absolute,
// thus gopathDir too, and that it exists.
d := prefixLen(segments(gopathDir), absFileDir)
// If there are multiple matches,
// prefer the innermost enclosing directory
// (smallest d).
if d >= 0 && d < minD {
minD = d
importPath = strings.Join(absFileDir[len(absFileDir)-minD:], string(os.PathSeparator))
}
}
if importPath == "" {
err = fmt.Errorf("can't find package for file %s", filename)
}
return
}
func segments(path string) []string {
return strings.Split(path, string(os.PathSeparator))
}
// prefixLen returns the length of the remainder of y if x is a prefix
// of y, a negative number otherwise.
func prefixLen(x, y []string) int {
d := len(y) - len(x)
if d >= 0 {
for i := range x {
if y[i] != x[i] {
return -1 // not a prefix
}
}
}
return d
}
// sameFile returns true if x and y have the same basename and denote
// the same file.
//
func sameFile(x, y string) bool {
if x == y {
return true
}
if filepath.Base(x) == filepath.Base(y) { // (optimisation)
if xi, err := os.Stat(x); err == nil {
if yi, err := os.Stat(y); err == nil {
return os.SameFile(xi, yi)
}
}
}
return false
}