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cmd/cloner, cmd/viewer, util/codegen: add support for generic types and interfaces

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This adds support for generic types and interfaces to our cloner and viewer codegens.
It updates these packages to determine whether to make shallow or deep copies based
on the type parameter constraints. Additionally, if a template parameter or an interface
type has View() and Clone() methods, we'll use them for getters and the cloner of the
owning structure.

Updates #12736

Signed-off-by: Nick Khyl <nickk@tailscale.com>
This commit is contained in:
Nick Khyl
2024-07-08 10:11:00 -05:00
committed by Nick Khyl
parent b7c3cfe049
commit fc28c8e7f3
9 changed files with 1039 additions and 114 deletions
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87
cmd/cloner/cloner.go
View File

@ -91,16 +91,19 @@ func gen(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named) {
}
name := typ.Obj().Name()
typeParams := typ.Origin().TypeParams()
_, typeParamNames := codegen.FormatTypeParams(typeParams, it)
nameWithParams := name + typeParamNames
fmt.Fprintf(buf, "// Clone makes a deep copy of %s.\n", name)
fmt.Fprintf(buf, "// The result aliases no memory with the original.\n")
fmt.Fprintf(buf, "func (src *%s) Clone() *%s {\n", name, name)
fmt.Fprintf(buf, "func (src *%s) Clone() *%s {\n", nameWithParams, nameWithParams)
writef := func(format string, args ...any) {
fmt.Fprintf(buf, "\t"+format+"\n", args...)
}
writef("if src == nil {")
writef("\treturn nil")
writef("}")
writef("dst := new(%s)", name)
writef("dst := new(%s)", nameWithParams)
writef("*dst = *src")
for i := range t.NumFields() {
fname := t.Field(i).Name()
@ -126,16 +129,23 @@ func gen(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named) {
writef("dst.%s = make([]%s, len(src.%s))", fname, n, fname)
writef("for i := range dst.%s {", fname)
if ptr, isPtr := ft.Elem().(*types.Pointer); isPtr {
if _, isBasic := ptr.Elem().Underlying().(*types.Basic); isBasic {
it.Import("tailscale.com/types/ptr")
writef("if src.%s[i] == nil { dst.%s[i] = nil } else {", fname, fname)
writef("\tdst.%s[i] = ptr.To(*src.%s[i])", fname, fname)
writef("}")
writef("if src.%s[i] == nil { dst.%s[i] = nil } else {", fname, fname)
if codegen.ContainsPointers(ptr.Elem()) {
if _, isIface := ptr.Elem().Underlying().(*types.Interface); isIface {
it.Import("tailscale.com/types/ptr")
writef("\tdst.%s[i] = ptr.To((*src.%s[i]).Clone())", fname, fname)
} else {
writef("\tdst.%s[i] = src.%s[i].Clone()", fname, fname)
}
} else {
writef("\tdst.%s[i] = src.%s[i].Clone()", fname, fname)
it.Import("tailscale.com/types/ptr")
writef("\tdst.%s[i] = ptr.To(*src.%s[i])", fname, fname)
}
writef("}")
} else if ft.Elem().String() == "encoding/json.RawMessage" {
writef("\tdst.%s[i] = append(src.%s[i][:0:0], src.%s[i]...)", fname, fname, fname)
} else if _, isIface := ft.Elem().Underlying().(*types.Interface); isIface {
writef("\tdst.%s[i] = src.%s[i].Clone()", fname, fname)
} else {
writef("\tdst.%s[i] = *src.%s[i].Clone()", fname, fname)
}
@ -145,14 +155,19 @@ func gen(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named) {
writef("dst.%s = append(src.%s[:0:0], src.%s...)", fname, fname, fname)
}
case *types.Pointer:
if named, _ := ft.Elem().(*types.Named); named != nil && codegen.ContainsPointers(ft.Elem()) {
base := ft.Elem()
hasPtrs := codegen.ContainsPointers(base)
if named, _ := base.(*types.Named); named != nil && hasPtrs {
writef("dst.%s = src.%s.Clone()", fname, fname)
continue
}
it.Import("tailscale.com/types/ptr")
writef("if dst.%s != nil {", fname)
writef("\tdst.%s = ptr.To(*src.%s)", fname, fname)
if codegen.ContainsPointers(ft.Elem()) {
if _, isIface := base.Underlying().(*types.Interface); isIface && hasPtrs {
writef("\tdst.%s = ptr.To((*src.%s).Clone())", fname, fname)
} else if !hasPtrs {
writef("\tdst.%s = ptr.To(*src.%s)", fname, fname)
} else {
writef("\t" + `panic("TODO pointers in pointers")`)
}
writef("}")
@ -172,18 +187,50 @@ func gen(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named) {
writef("if dst.%s != nil {", fname)
writef("\tdst.%s = map[%s]%s{}", fname, it.QualifiedName(ft.Key()), it.QualifiedName(elem))
writef("\tfor k, v := range src.%s {", fname)
switch elem.(type) {
switch elem := elem.Underlying().(type) {
case *types.Pointer:
writef("\t\tdst.%s[k] = v.Clone()", fname)
writef("\t\tif v == nil { dst.%s[k] = nil } else {", fname)
if base := elem.Elem().Underlying(); codegen.ContainsPointers(base) {
if _, isIface := base.(*types.Interface); isIface {
it.Import("tailscale.com/types/ptr")
writef("\t\t\tdst.%s[k] = ptr.To((*v).Clone())", fname)
} else {
writef("\t\t\tdst.%s[k] = v.Clone()", fname)
}
} else {
it.Import("tailscale.com/types/ptr")
writef("\t\t\tdst.%s[k] = ptr.To(*v)", fname)
}
writef("}")
case *types.Interface:
if cloneResultType := methodResultType(elem, "Clone"); cloneResultType != nil {
if _, isPtr := cloneResultType.(*types.Pointer); isPtr {
writef("\t\tdst.%s[k] = *(v.Clone())", fname)
} else {
writef("\t\tdst.%s[k] = v.Clone()", fname)
}
} else {
writef(`panic("%s (%v) does not have a Clone method")`, fname, elem)
}
default:
writef("\t\tdst.%s[k] = *(v.Clone())", fname)
}
writef("\t}")
writef("}")
} else {
it.Import("maps")
writef("\tdst.%s = maps.Clone(src.%s)", fname, fname)
}
case *types.Interface:
// If ft is an interface with a "Clone() ft" method, it can be used to clone the field.
// This includes scenarios where ft is a constrained type parameter.
if cloneResultType := methodResultType(ft, "Clone"); cloneResultType.Underlying() == ft {
writef("dst.%s = src.%s.Clone()", fname, fname)
continue
}
writef(`panic("%s (%v) does not have a compatible Clone method")`, fname, ft)
default:
writef(`panic("TODO: %s (%T)")`, fname, ft)
}
@ -191,7 +238,7 @@ func gen(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named) {
writef("return dst")
fmt.Fprintf(buf, "}\n\n")
buf.Write(codegen.AssertStructUnchanged(t, name, "Clone", it))
buf.Write(codegen.AssertStructUnchanged(t, name, typeParams, "Clone", it))
}
// hasBasicUnderlying reports true when typ.Underlying() is a slice or a map.
@ -203,3 +250,15 @@ func hasBasicUnderlying(typ types.Type) bool {
return false
}
}
func methodResultType(typ types.Type, method string) types.Type {
viewMethod := codegen.LookupMethod(typ, method)
if viewMethod == nil {
return nil
}
sig, ok := viewMethod.Type().(*types.Signature)
if !ok || sig.Results().Len() != 1 {
return nil
}
return sig.Results().At(0).Type()
}