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conversion-gen: support recursive types #49747

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Jul 31, 2017
Merged

conversion-gen: support recursive types #49747

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24 changes: 18 additions & 6 deletions staging/src/k8s.io/kube-gen/cmd/conversion-gen/generators/conversion.go
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Original file line number Diff line number Diff line change
Expand Up @@ -329,6 +329,12 @@ func (e equalMemoryTypes) Skip(a, b *types.Type) {
}

func (e equalMemoryTypes) Equal(a, b *types.Type) bool {
// alreadyVisitedTypes holds all the types that have already been checked in the structural type recursion.
alreadyVisitedTypes := make(map[*types.Type]bool)
return e.cachingEqual(a, b, alreadyVisitedTypes)
}

func (e equalMemoryTypes) cachingEqual(a, b *types.Type, alreadyVisitedTypes map[*types.Type]bool) bool {
if a == b {
return true
}
Expand All @@ -338,36 +344,42 @@ func (e equalMemoryTypes) Equal(a, b *types.Type) bool {
if equal, ok := e[conversionPair{b, a}]; ok {
return equal
}
result := e.equal(a, b)
result := e.equal(a, b, alreadyVisitedTypes)
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Wondering, do we need the parameter inEqual at all? Can't we create the empty map here?

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We can't do that because we need the populated map in line 366, 372, 374 and 376 below. If we create an empty map here and those lines are executed, they will see the type as "not visited" - which will defeat our purpose. :)

Also, tried it out. Gives the goroutine stack exceeds 1000000000-byte limit error.

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oh, didn't realize the recursion goes through Equal and not equal.

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But, everything here in Equal can be moved to equal and then we can recursively call equal instead of Equal, can't it? Then my suggestion should work.

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Doesn't make the code easier to read though. Let's leave it as it is.

e[conversionPair{a, b}] = result
e[conversionPair{b, a}] = result
return result
}

func (e equalMemoryTypes) equal(a, b *types.Type) bool {
func (e equalMemoryTypes) equal(a, b *types.Type, alreadyVisitedTypes map[*types.Type]bool) bool {
in, out := unwrapAlias(a), unwrapAlias(b)
switch {
case in == out:
return true
case in.Kind == out.Kind:
// if the type exists already, return early to avoid recursion
if alreadyVisitedTypes[in] {
return true
}
alreadyVisitedTypes[in] = true

switch in.Kind {
case types.Struct:
if len(in.Members) != len(out.Members) {
return false
}
for i, inMember := range in.Members {
outMember := out.Members[i]
if !e.Equal(inMember.Type, outMember.Type) {
if !e.cachingEqual(inMember.Type, outMember.Type, alreadyVisitedTypes) {
return false
}
}
return true
case types.Pointer:
return e.Equal(in.Elem, out.Elem)
return e.cachingEqual(in.Elem, out.Elem, alreadyVisitedTypes)
case types.Map:
return e.Equal(in.Key, out.Key) && e.Equal(in.Elem, out.Elem)
return e.cachingEqual(in.Key, out.Key, alreadyVisitedTypes) && e.cachingEqual(in.Elem, out.Elem, alreadyVisitedTypes)
case types.Slice:
return e.Equal(in.Elem, out.Elem)
return e.cachingEqual(in.Elem, out.Elem, alreadyVisitedTypes)
case types.Interface:
// TODO: determine whether the interfaces are actually equivalent - for now, they must have the
// same type.
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