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// TODO: test swap corresponding types (e.g. u1 <-> u2 and u2 <-> u1)
// TODO: test exported alias refers to something in another package -- does correspondence work then?
// TODO: CODE COVERAGE
// TODO: note that we may miss correspondences because we bail early when we compare a signature (e.g. when lengths differ; we could do up to the shorter)
// TODO: if you add an unexported method to an exposed interface, you have to check that
// every exposed type that previously implemented the interface still does. Otherwise
// an external assignment of the exposed type to the interface type could fail.
// TODO: check constant values: large values aren't representable by some types.
// TODO: Document all the incompatibilities we don't check for.
package apidiff
import (
"fmt"
"go/constant"
"go/token"
"go/types"
)
// Changes reports on the differences between the APIs of the old and new packages.
// It classifies each difference as either compatible or incompatible (breaking.) For
// a detailed discussion of what constitutes an incompatible change, see the package
// documentation.
func Changes(old, new *types.Package) Report {
d := newDiffer(old, new)
d.checkPackage()
r := Report{}
for _, m := range d.incompatibles.collect() {
r.Changes = append(r.Changes, Change{Message: m, Compatible: false})
}
for _, m := range d.compatibles.collect() {
r.Changes = append(r.Changes, Change{Message: m, Compatible: true})
}
return r
}
type differ struct {
old, new *types.Package
// Correspondences between named types.
// Even though it is the named types (*types.Named) that correspond, we use
// *types.TypeName as a map key because they are canonical.
// The values can be either named types or basic types.
correspondMap map[*types.TypeName]types.Type
// Messages.
incompatibles messageSet
compatibles messageSet
}
func newDiffer(old, new *types.Package) *differ {
return &differ{
old: old,
new: new,
correspondMap: map[*types.TypeName]types.Type{},
incompatibles: messageSet{},
compatibles: messageSet{},
}
}
func (d *differ) incompatible(obj types.Object, part, format string, args ...interface{}) {
addMessage(d.incompatibles, obj, part, format, args)
}
func (d *differ) compatible(obj types.Object, part, format string, args ...interface{}) {
addMessage(d.compatibles, obj, part, format, args)
}
func addMessage(ms messageSet, obj types.Object, part, format string, args []interface{}) {
ms.add(obj, part, fmt.Sprintf(format, args...))
}
func (d *differ) checkPackage() {
// Old changes.
for _, name := range d.old.Scope().Names() {
oldobj := d.old.Scope().Lookup(name)
if !oldobj.Exported() {
continue
}
newobj := d.new.Scope().Lookup(name)
if newobj == nil {
d.incompatible(oldobj, "", "removed")
continue
}
d.checkObjects(oldobj, newobj)
}
// New additions.
for _, name := range d.new.Scope().Names() {
newobj := d.new.Scope().Lookup(name)
if newobj.Exported() && d.old.Scope().Lookup(name) == nil {
d.compatible(newobj, "", "added")
}
}
// Whole-package satisfaction.
// For every old exposed interface oIface and its corresponding new interface nIface...
for otn1, nt1 := range d.correspondMap {
oIface, ok := otn1.Type().Underlying().(*types.Interface)
if !ok {
continue
}
nIface, ok := nt1.Underlying().(*types.Interface)
if !ok {
// If nt1 isn't an interface but otn1 is, then that's an incompatibility that
// we've already noticed, so there's no need to do anything here.
continue
}
// For every old type that implements oIface, its corresponding new type must implement
// nIface.
for otn2, nt2 := range d.correspondMap {
if otn1 == otn2 {
continue
}
if types.Implements(otn2.Type(), oIface) && !types.Implements(nt2, nIface) {
d.incompatible(otn2, "", "no longer implements %s", objectString(otn1))
}
}
}
}
func (d *differ) checkObjects(old, new types.Object) {
switch old := old.(type) {
case *types.Const:
if new, ok := new.(*types.Const); ok {
d.constChanges(old, new)
return
}
case *types.Var:
if new, ok := new.(*types.Var); ok {
d.checkCorrespondence(old, "", old.Type(), new.Type())
return
}
case *types.Func:
switch new := new.(type) {
case *types.Func:
d.checkCorrespondence(old, "", old.Type(), new.Type())
return
case *types.Var:
d.compatible(old, "", "changed from func to var")
d.checkCorrespondence(old, "", old.Type(), new.Type())
return
}
case *types.TypeName:
if new, ok := new.(*types.TypeName); ok {
d.checkCorrespondence(old, "", old.Type(), new.Type())
return
}
default:
panic("unexpected obj type")
}
// Here if kind of type changed.
d.incompatible(old, "", "changed from %s to %s",
objectKindString(old), objectKindString(new))
}
// Compare two constants.
func (d *differ) constChanges(old, new *types.Const) {
ot := old.Type()
nt := new.Type()
// Check for change of type.
if !d.correspond(ot, nt) {
d.typeChanged(old, "", ot, nt)
return
}
// Check for change of value.
// We know the types are the same, so constant.Compare shouldn't panic.
if !constant.Compare(old.Val(), token.EQL, new.Val()) {
d.incompatible(old, "", "value changed from %s to %s", old.Val(), new.Val())
}
}
func objectKindString(obj types.Object) string {
switch obj.(type) {
case *types.Const:
return "const"
case *types.Var:
return "var"
case *types.Func:
return "func"
case *types.TypeName:
return "type"
default:
return "???"
}
}
func (d *differ) checkCorrespondence(obj types.Object, part string, old, new types.Type) {
if !d.correspond(old, new) {
d.typeChanged(obj, part, old, new)
}
}
func (d *differ) typeChanged(obj types.Object, part string, old, new types.Type) {
old = removeNamesFromSignature(old)
new = removeNamesFromSignature(new)
olds := types.TypeString(old, types.RelativeTo(d.old))
news := types.TypeString(new, types.RelativeTo(d.new))
d.incompatible(obj, part, "changed from %s to %s", olds, news)
}
// go/types always includes the argument and result names when formatting a signature.
// Since these can change without affecting compatibility, we don't want users to
// be distracted by them, so we remove them.
func removeNamesFromSignature(t types.Type) types.Type {
sig, ok := t.(*types.Signature)
if !ok {
return t
}
dename := func(p *types.Tuple) *types.Tuple {
var vars []*types.Var
for i := 0; i < p.Len(); i++ {
v := p.At(i)
vars = append(vars, types.NewVar(v.Pos(), v.Pkg(), "", v.Type()))
}
return types.NewTuple(vars...)
}
return types.NewSignature(sig.Recv(), dename(sig.Params()), dename(sig.Results()), sig.Variadic())
}
|
