feat: replace mapping generation with checked copy utilities

2026-09-25 17:27:28 +08:00
parent ad9257d202
commit fd83235ce7
45 changed files with 2366 additions and 1872 deletions
--- a/copyx/copy.go
+++ b/copyx/copy.go
@@ -0,0 +1,537 @@
+package copyx
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+	"runtime"
+	"sort"
+	"sync"
+)
+
+var (
+	ErrType            = errors.New("copyx: incompatible types")
+	ErrNil             = errors.New("copyx: nil cannot fill a non-nullable target")
+	ErrField           = errors.New("copyx: unmatched field")
+	ErrUnsupported     = errors.New("copyx: unsupported value; provide an explicit data converter")
+	ErrSharedReference = errors.New("copyx: deep copy retains a mutable source reference")
+	ErrLimit           = errors.New("copyx: traversal limit exceeded")
+)
+
+// Error describes a field/index path without recording the source value.
+type Error struct {
+	Path  string
+	Cause error
+}
+
+func (e *Error) Error() string        { return e.Path + ": " + e.Cause.Error() }
+func (e *Error) Unwrap() error        { return e.Cause }
+func at(path string, err error) error { return &Error{Path: path, Cause: err} }
+
+func Copy(target, source any, options ...Option) error {
+	c, err := New(options...)
+	if err != nil {
+		return err
+	}
+	return c.Copy(target, source)
+}
+
+// Clone always makes a deep copy. Nil and empty collections stay distinct.
+func Clone[T any](source T, options ...Option) (T, error) {
+	var target T
+	options = append(append([]Option(nil), options...), WithDeepCopy())
+	err := Copy(&target, source, options...)
+	return target, err
+}
+
+// Copy stages the complete result and only assigns target on success. User
+// converter side effects (including mutation of source) cannot be rolled back.
+// Caller must synchronize concurrent access to source and target themselves.
+func (c *Copier) Copy(target, source any) error {
+	// Alias indexes contain addresses only. Keep the original graph alive until
+	// validation and commit finish so the GC cannot recycle any indexed address.
+	defer func() { runtime.KeepAlive(source) }()
+	if c == nil {
+		return errors.New("copyx: nil Copier")
+	}
+	dst := reflect.ValueOf(target)
+	if !dst.IsValid() || dst.Kind() != reflect.Pointer || dst.IsNil() {
+		return errors.New("copyx: target must be a non-nil pointer")
+	}
+	src := reflect.ValueOf(source)
+	s := state{options: &c.options, seen: map[visit]reflect.Value{}}
+	if c.options.deep {
+		var err error
+		s.graph, err = sourceGraph(src)
+		if err != nil {
+			return err
+		}
+		if src.IsValid() && src.Kind() == reflect.Pointer && !src.IsNil() && dst.Elem().Kind() == reflect.Struct {
+			id := identity(src)
+			s.valueRoot = &id
+		}
+	}
+	out, err := s.walk(src, dst.Elem(), dst.Elem().Type(), "$", 0)
+	if err != nil {
+		return err
+	}
+	if s.graph != nil {
+		if err = s.graph.audit(out); err != nil {
+			return err
+		}
+	}
+	dst.Elem().Set(out)
+	return nil
+}
+
+type visit struct {
+	reference
+	target reflect.Type
+}
+type state struct {
+	options   *settings
+	seen      map[visit]reflect.Value
+	graph     *graph
+	nodes     int
+	allocated uint64
+	valueRoot *reference
+}
+
+func (s *state) reserve(count int, size uintptr, path string) error {
+	if count < 0 || (count > 0 && uint64(size) > maxCopyBytes/uint64(count)) {
+		return at(path, ErrLimit)
+	}
+	s.allocated += uint64(count) * uint64(size)
+	if s.allocated > maxCopyBytes {
+		return at(path, ErrLimit)
+	}
+	return nil
+}
+
+func nullable(k reflect.Kind) bool {
+	switch k {
+	case reflect.Pointer, reflect.Map, reflect.Slice, reflect.Interface, reflect.Func, reflect.Chan:
+		return true
+	}
+	return false
+}
+func baseValue(base reflect.Value, t reflect.Type) reflect.Value {
+	if base.IsValid() && base.Type() == t {
+		return base
+	}
+	return reflect.Zero(t)
+}
+func (s *state) walk(src, base reflect.Value, t reflect.Type, path string, depth int) (reflect.Value, error) {
+	s.nodes++
+	if depth > maxDepth || s.nodes > maxNodes {
+		return reflect.Value{}, at(path, ErrLimit)
+	}
+	base = baseValue(base, t)
+	if !shallowSafe(t) {
+		return reflect.Value{}, at(path, ErrUnsupported)
+	}
+	if src.IsValid() && !src.CanInterface() {
+		return reflect.Value{}, at(path, ErrUnsupported)
+	}
+	// Exact converters also receive typed nils and zeros. No method calls,
+	// Scanner/Valuer invocation or implicit numeric conversion is attempted.
+	if src.IsValid() {
+		if convert, ok := s.options.converters[pair{src.Type(), t}]; ok {
+			out, err := convert(src)
+			if err != nil {
+				return reflect.Value{}, at(path, err)
+			}
+			if s.graph != nil {
+				if err = s.graph.audit(out); err != nil {
+					return reflect.Value{}, at(path, err)
+				}
+			}
+			return out, nil
+		}
+	}
+	if !src.IsValid() || (nullable(src.Kind()) && src.IsNil()) {
+		if src.IsValid() && !s.nilCompatible(src.Type(), t, map[pair]bool{}) {
+			return reflect.Value{}, at(path, ErrType)
+		}
+		if s.options.nilPolicy == NilSkip {
+			return base, nil
+		}
+		if nullable(t.Kind()) || s.options.nilPolicy == NilZero {
+			return reflect.Zero(t), nil
+		}
+		return reflect.Value{}, at(path, ErrNil)
+	}
+	if s.options.skipZero && src.IsZero() {
+		if !s.nilCompatible(src.Type(), t, map[pair]bool{}) {
+			return reflect.Value{}, at(path, ErrType)
+		}
+		return base, nil
+	}
+	if src.Type() == t && len(s.options.converters) == 0 && len(s.options.fields) == 0 && !s.options.skipZero && s.options.nilPolicy != NilSkip {
+		if !s.options.deep || simpleValue(t) {
+			return src, nil
+		}
+	}
+	if src.Kind() == reflect.Interface {
+		return s.walk(src.Elem(), base, t, path, depth+1)
+	}
+	if t.Kind() == reflect.Interface {
+		if !src.Type().Implements(t) {
+			return reflect.Value{}, at(path, ErrType)
+		}
+		out, err := s.walk(src, reflect.Value{}, src.Type(), path, depth+1)
+		if err != nil {
+			return reflect.Value{}, err
+		}
+		v := reflect.New(t).Elem()
+		v.Set(out)
+		return v, nil
+	}
+	if s.options.deep && forbidden(t) {
+		return reflect.Value{}, at(path, ErrUnsupported)
+	}
+	if src.Kind() == reflect.Pointer && t.Kind() != reflect.Pointer {
+		return s.walk(src.Elem(), base, t, path, depth+1)
+	}
+	if t.Kind() == reflect.Pointer {
+		if !s.options.deep && src.Type() == t {
+			return src, nil
+		}
+		if src.Kind() == reflect.Pointer {
+			key := visit{identity(src), t}
+			if s.valueRoot != nil && key.reference == *s.valueRoot {
+				return reflect.Value{}, at(path, fmt.Errorf("%w: cyclic root must retain its pointer; use Clone(source) or Copy(&targetPointer, source)", ErrUnsupported))
+			}
+			if prior, ok := s.seen[key]; ok {
+				return prior, nil
+			}
+		}
+		if err := s.reserve(1, t.Elem().Size(), path); err != nil {
+			return reflect.Value{}, err
+		}
+		out := reflect.New(t.Elem())
+		if out.Type() != t {
+			out = out.Convert(t)
+		}
+		if src.Kind() == reflect.Pointer {
+			key := visit{identity(src), t}
+			s.seen[key] = out
+			src = src.Elem()
+		}
+		var childBase reflect.Value
+		if !base.IsNil() {
+			childBase = base.Elem()
+		}
+		value, err := s.walk(src, childBase, t.Elem(), path, depth+1)
+		if err != nil {
+			return reflect.Value{}, err
+		}
+		out.Elem().Set(value)
+		return out, nil
+	}
+	if src.Kind() != t.Kind() {
+		return reflect.Value{}, at(path, fmt.Errorf("%w: %s -> %s", ErrType, src.Type(), t))
+	}
+	if t == timeType && src.Type() == t {
+		return src, nil
+	}
+	switch t.Kind() {
+	case reflect.Struct:
+		return s.structure(src, base, t, path, depth)
+	case reflect.Slice:
+		if !s.options.deep && src.Type() == t {
+			return src, nil
+		}
+		key := visit{identity(src), t}
+		if prior, ok := s.seen[key]; ok {
+			return prior, nil
+		}
+		if err := s.reserve(src.Len(), t.Elem().Size(), path); err != nil {
+			return reflect.Value{}, err
+		}
+		out := reflect.MakeSlice(t, src.Len(), src.Len())
+		s.seen[key] = out
+		if src.Type() == t && len(s.options.converters) == 0 && len(s.options.fields) == 0 && simpleValue(t.Elem()) {
+			reflect.Copy(out, src)
+			return out, nil
+		}
+		for i := 0; i < src.Len(); i++ {
+			v, err := s.walk(src.Index(i), reflect.Value{}, t.Elem(), fmt.Sprintf("%s[%d]", path, i), depth+1)
+			if err != nil {
+				return reflect.Value{}, err
+			}
+			out.Index(i).Set(v)
+		}
+		return out, nil
+	case reflect.Array:
+		if src.Len() != t.Len() {
+			return reflect.Value{}, at(path, ErrType)
+		}
+		if err := s.reserve(1, t.Size(), path); err != nil {
+			return reflect.Value{}, err
+		}
+		out := reflect.New(t).Elem()
+		for i := 0; i < src.Len(); i++ {
+			v, err := s.walk(src.Index(i), base.Index(i), t.Elem(), fmt.Sprintf("%s[%d]", path, i), depth+1)
+			if err != nil {
+				return reflect.Value{}, err
+			}
+			out.Index(i).Set(v)
+		}
+		return out, nil
+	case reflect.Map:
+		if !s.options.deep && src.Type() == t {
+			return src, nil
+		}
+		key := visit{identity(src), t}
+		if prior, ok := s.seen[key]; ok {
+			return prior, nil
+		}
+		if err := s.reserve(src.Len(), t.Key().Size()+t.Elem().Size()+32, path); err != nil {
+			return reflect.Value{}, err
+		}
+		out := reflect.MakeMapWithSize(t, src.Len())
+		s.seen[key] = out
+		it := src.MapRange()
+		for it.Next() {
+			k, err := s.walk(it.Key(), reflect.Value{}, t.Key(), path+"[key]", depth+1)
+			if err != nil {
+				return reflect.Value{}, err
+			}
+			if !k.Comparable() {
+				return reflect.Value{}, at(path+"[key]", ErrType)
+			}
+			if out.MapIndex(k).IsValid() {
+				return reflect.Value{}, at(path+"[key]", errors.New("copyx: key conversion collision"))
+			}
+			v, err := s.walk(it.Value(), reflect.Value{}, t.Elem(), path+"[value]", depth+1)
+			if err != nil {
+				return reflect.Value{}, err
+			}
+			out.SetMapIndex(k, v)
+		}
+		return out, nil
+	case reflect.Func, reflect.Chan, reflect.UnsafePointer:
+		if s.options.deep {
+			return reflect.Value{}, at(path, ErrUnsupported)
+		}
+	}
+	if src.Type() != t {
+		return reflect.Value{}, at(path, fmt.Errorf("%w: %s -> %s", ErrType, src.Type(), t))
+	}
+	return src, nil
+}
+
+var fieldTypes sync.Map
+
+func exportedFields(t reflect.Type) map[string]reflect.StructField {
+	if known, ok := fieldTypes.Load(t); ok {
+		return known.(map[string]reflect.StructField)
+	}
+	out := map[string]reflect.StructField{}
+	for _, f := range reflect.VisibleFields(t) {
+		if f.PkgPath != "" {
+			continue
+		}
+		kind := f.Type.Kind()
+		if kind == reflect.Pointer {
+			kind = f.Type.Elem().Kind()
+		}
+		if f.Anonymous && kind == reflect.Struct {
+			continue
+		}
+		out[f.Name] = f
+	}
+	actual, _ := fieldTypes.LoadOrStore(t, out)
+	return actual.(map[string]reflect.StructField)
+}
+
+func (s *state) nilCompatible(from, to reflect.Type, seen map[pair]bool) bool {
+	key := pair{from, to}
+	if seen[key] {
+		return true
+	}
+	seen[key] = true
+	if from == to {
+		return true
+	}
+	if _, ok := s.options.converters[key]; ok {
+		return true
+	}
+	if to.Kind() == reflect.Interface {
+		return from.Implements(to)
+	}
+	if from.Kind() == reflect.Pointer {
+		return s.nilCompatible(from.Elem(), to, seen)
+	}
+	if to.Kind() == reflect.Pointer {
+		return s.nilCompatible(from, to.Elem(), seen)
+	}
+	if from.Kind() != to.Kind() {
+		return false
+	}
+	switch from.Kind() {
+	case reflect.Struct:
+		// Nil must not hide a structurally incompatible type pair. There are no
+		// field values to visit, but coverage and conversion types still apply.
+		for i := 0; i < to.NumField(); i++ {
+			if to.Field(i).PkgPath != "" {
+				return false
+			}
+		}
+		sources, targets := exportedFields(from), exportedFields(to)
+		rules := s.options.fields[key]
+		if rules == nil {
+			rules = &fields{}
+		}
+		reverse, used := map[string]string{}, map[string]bool{}
+		for a, b := range rules.names {
+			reverse[b] = a
+		}
+		for name, target := range targets {
+			if rules.ignoreTarget[name] {
+				continue
+			}
+			srcName := name
+			if renamed, ok := reverse[name]; ok {
+				srcName = renamed
+			}
+			source, ok := sources[srcName]
+			if !ok || rules.ignoreSource[srcName] || !s.nilCompatible(source.Type, target.Type, seen) {
+				return false
+			}
+			used[srcName] = true
+		}
+		if s.options.strict {
+			for name := range sources {
+				if !used[name] && !rules.ignoreSource[name] {
+					return false
+				}
+			}
+		}
+		return true
+	case reflect.Slice:
+		return s.nilCompatible(from.Elem(), to.Elem(), seen)
+	case reflect.Map:
+		return s.nilCompatible(from.Key(), to.Key(), seen) && s.nilCompatible(from.Elem(), to.Elem(), seen)
+	case reflect.Array:
+		return from.Len() == to.Len() && s.nilCompatible(from.Elem(), to.Elem(), seen)
+	}
+	return false
+}
+func fieldValue(v reflect.Value, index []int) (reflect.Value, bool) {
+	for _, i := range index {
+		if v.Kind() == reflect.Pointer {
+			if v.IsNil() {
+				return reflect.Value{}, false
+			}
+			v = v.Elem()
+		}
+		v = v.Field(i)
+	}
+	return v, true
+}
+func setField(v reflect.Value, index []int, value reflect.Value) error {
+	for j, i := range index {
+		field := v.Field(i)
+		if !field.CanSet() {
+			return ErrUnsupported
+		}
+		if j == len(index)-1 {
+			field.Set(value)
+			return nil
+		}
+		if field.Kind() == reflect.Pointer {
+			// Detach embedded destination pointers before editing promoted fields.
+			fresh := reflect.New(field.Type().Elem())
+			if !field.IsNil() {
+				fresh.Elem().Set(field.Elem())
+			}
+			field.Set(fresh)
+			v = fresh.Elem()
+		} else {
+			v = field
+		}
+	}
+	return nil
+}
+func (s *state) structure(src, base reflect.Value, t reflect.Type, path string, depth int) (reflect.Value, error) {
+	if err := s.reserve(1, t.Size(), path); err != nil {
+		return reflect.Value{}, err
+	}
+	out := reflect.New(t).Elem()
+	out.Set(base)
+	if src.Type() == t {
+		// Private scalar state may be assigned as part of its whole value; mutable
+		// private state requires a converter, never unsafe writes or silent loss.
+		for i := 0; i < t.NumField(); i++ {
+			f := t.Field(i)
+			if f.PkgPath != "" && s.options.deep && privateMutable(f.Type) {
+				return reflect.Value{}, at(path+"."+f.Name, ErrUnsupported)
+			}
+		}
+		out.Set(src)
+	} else {
+		for i := 0; i < t.NumField(); i++ {
+			if t.Field(i).PkgPath != "" {
+				return reflect.Value{}, at(path, ErrUnsupported)
+			}
+		}
+	}
+	from, to := exportedFields(src.Type()), exportedFields(t)
+	rules := s.options.fields[pair{src.Type(), t}]
+	if rules == nil {
+		rules = &fields{map[string]string{}, map[string]bool{}, map[string]bool{}}
+	}
+	reverse := map[string]string{}
+	for a, b := range rules.names {
+		reverse[b] = a
+	}
+	names := make([]string, 0, len(to))
+	for n := range to {
+		names = append(names, n)
+	}
+	sort.Strings(names)
+	used := map[string]bool{}
+	for _, name := range names {
+		target := to[name]
+		old, _ := fieldValue(base, target.Index)
+		if rules.ignoreTarget[name] {
+			if !old.IsValid() {
+				old = reflect.Zero(target.Type)
+			}
+			if err := setField(out, target.Index, old); err != nil {
+				return reflect.Value{}, at(path+"."+name, err)
+			}
+			continue
+		}
+		srcName := name
+		if renamed, ok := reverse[name]; ok {
+			srcName = renamed
+		}
+		source, ok := from[srcName]
+		if !ok || rules.ignoreSource[srcName] {
+			return reflect.Value{}, at(path+"."+name, ErrField)
+		}
+		used[srcName] = true
+		v, ok := fieldValue(src, source.Index)
+		if !ok {
+			return reflect.Value{}, at(path+"."+name, ErrNil)
+		}
+		value, err := s.walk(v, old, target.Type, path+"."+name, depth+1)
+		if err != nil {
+			return reflect.Value{}, err
+		}
+		if err = setField(out, target.Index, value); err != nil {
+			return reflect.Value{}, at(path+"."+name, err)
+		}
+	}
+	if s.options.strict {
+		for name := range from {
+			if !used[name] && !rules.ignoreSource[name] {
+				return reflect.Value{}, at(path+"."+name, ErrField)
+			}
+		}
+	}
+	return out, nil
+}