Merge branch 'master' of ssh://git.pyer.club:2222/kingecg/goxml

atom_test.go

@@ -0,0 +1,56 @@
+// Copyright 2011 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 goxml
+
+import "time"
+
+var atomValue = &Feed{
+	XMLName: Name{"http://www.w3.org/2005/Atom", "feed"},
+	Title:   "Example Feed",
+	Link:    []Link{{Href: "http://example.org/"}},
+	Updated: ParseTime("2003-12-13T18:30:02Z"),
+	Author:  Person{Name: "John Doe"},
+	ID:      "urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6",
+
+	Entry: []Entry{
+		{
+			Title:   "Atom-Powered Robots Run Amok",
+			Link:    []Link{{Href: "http://example.org/2003/12/13/atom03"}},
+			ID:      "urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a",
+			Updated: ParseTime("2003-12-13T18:30:02Z"),
+			Summary: NewText("Some text."),
+		},
+	},
+}
+
+var atomXML = `` +
+	`<feed xmlns="http://www.w3.org/2005/Atom" updated="2003-12-13T18:30:02Z">` +
+	`<title>Example Feed</title>` +
+	`<id>urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6</id>` +
+	`<link href="http://example.org/"></link>` +
+	`<author><name>John Doe</name><uri></uri><email></email></author>` +
+	`<entry>` +
+	`<title>Atom-Powered Robots Run Amok</title>` +
+	`<id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>` +
+	`<link href="http://example.org/2003/12/13/atom03"></link>` +
+	`<updated>2003-12-13T18:30:02Z</updated>` +
+	`<author><name></name><uri></uri><email></email></author>` +
+	`<summary>Some text.</summary>` +
+	`</entry>` +
+	`</feed>`
+
+func ParseTime(str string) time.Time {
+	t, err := time.Parse(time.RFC3339, str)
+	if err != nil {
+		panic(err)
+	}
+	return t
+}
+
+func NewText(text string) Text {
+	return Text{
+		Body: text,
+	}
+}

example_marshaling_test.go

@@ -0,0 +1,85 @@
+// Copyright 2018 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 goxml_test
+
+import (
+	"fmt"
+	"log"
+	"strings"
+
+	"git.pyer.club/kingecg/goxml"
+)
+
+type Animal int
+
+const (
+	Unknown Animal = iota
+	Gopher
+	Zebra
+)
+
+func (a *Animal) UnmarshalXML(d *goxml.Decoder, start goxml.StartElement) error {
+	var s string
+	if err := d.DecodeElement(&s, &start); err != nil {
+		return err
+	}
+	switch strings.ToLower(s) {
+	default:
+		*a = Unknown
+	case "gopher":
+		*a = Gopher
+	case "zebra":
+		*a = Zebra
+	}
+
+	return nil
+}
+
+func (a Animal) MarshalXML(e *goxml.Encoder, start goxml.StartElement) error {
+	var s string
+	switch a {
+	default:
+		s = "unknown"
+	case Gopher:
+		s = "gopher"
+	case Zebra:
+		s = "zebra"
+	}
+	return e.EncodeElement(s, start)
+}
+
+func Example_customMarshalXML() {
+	blob := `
+	<animals>
+		<animal>gopher</animal>
+		<animal>armadillo</animal>
+		<animal>zebra</animal>
+		<animal>unknown</animal>
+		<animal>gopher</animal>
+		<animal>bee</animal>
+		<animal>gopher</animal>
+		<animal>zebra</animal>
+	</animals>`
+	var zoo struct {
+		Animals []Animal `xml:"animal"`
+	}
+	if err := goxml.Unmarshal([]byte(blob), &zoo); err != nil {
+		log.Fatal(err)
+	}
+
+	census := make(map[Animal]int)
+	for _, animal := range zoo.Animals {
+		census[animal] += 1
+	}
+
+	fmt.Printf("Zoo Census:\n* Gophers: %d\n* Zebras:  %d\n* Unknown: %d\n",
+		census[Gopher], census[Zebra], census[Unknown])
+
+	// Output:
+	// Zoo Census:
+	// * Gophers: 3
+	// * Zebras:  2
+	// * Unknown: 3
+}

example_test.go

@@ -0,0 +1,152 @@
+// Copyright 2012 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 goxml_test
+
+import (
+	"fmt"
+	"os"
+
+	"git.pyer.club/kingecg/goxml"
+)
+
+func ExampleMarshalIndent() {
+	type Address struct {
+		City, State string
+	}
+	type Person struct {
+		XMLName   goxml.Name `xml:"person"`
+		Id        int        `xml:"id,attr"`
+		FirstName string     `xml:"name>first"`
+		LastName  string     `xml:"name>last"`
+		Age       int        `xml:"age"`
+		Height    float32    `xml:"height,omitempty"`
+		Married   bool
+		Address
+		Comment string `xml:",comment"`
+	}
+
+	v := &Person{Id: 13, FirstName: "John", LastName: "Doe", Age: 42}
+	v.Comment = " Need more details. "
+	v.Address = Address{"Hanga Roa", "Easter Island"}
+
+	output, err := goxml.MarshalIndent(v, "  ", "    ")
+	if err != nil {
+		fmt.Printf("error: %v\n", err)
+	}
+
+	os.Stdout.Write(output)
+	// Output:
+	//   <person id="13">
+	//       <name>
+	//           <first>John</first>
+	//           <last>Doe</last>
+	//       </name>
+	//       <age>42</age>
+	//       <Married>false</Married>
+	//       <City>Hanga Roa</City>
+	//       <State>Easter Island</State>
+	//       <!-- Need more details. -->
+	//   </person>
+}
+
+func ExampleEncoder() {
+	type Address struct {
+		City, State string
+	}
+	type Person struct {
+		XMLName   goxml.Name `xml:"person"`
+		Id        int        `xml:"id,attr"`
+		FirstName string     `xml:"name>first"`
+		LastName  string     `xml:"name>last"`
+		Age       int        `xml:"age"`
+		Height    float32    `xml:"height,omitempty"`
+		Married   bool
+		Address
+		Comment string `xml:",comment"`
+	}
+
+	v := &Person{Id: 13, FirstName: "John", LastName: "Doe", Age: 42}
+	v.Comment = " Need more details. "
+	v.Address = Address{"Hanga Roa", "Easter Island"}
+
+	enc := goxml.NewEncoder(os.Stdout)
+	enc.Indent("  ", "    ")
+	if err := enc.Encode(v); err != nil {
+		fmt.Printf("error: %v\n", err)
+	}
+
+	// Output:
+	//   <person id="13">
+	//       <name>
+	//           <first>John</first>
+	//           <last>Doe</last>
+	//       </name>
+	//       <age>42</age>
+	//       <Married>false</Married>
+	//       <City>Hanga Roa</City>
+	//       <State>Easter Island</State>
+	//       <!-- Need more details. -->
+	//   </person>
+}
+
+// This example demonstrates unmarshaling an XML excerpt into a value with
+// some preset fields. Note that the Phone field isn't modified and that
+// the XML <Company> element is ignored. Also, the Groups field is assigned
+// considering the element path provided in its tag.
+func ExampleUnmarshal() {
+	type Email struct {
+		Where string `xml:"where,attr"`
+		Addr  string
+	}
+	type Address struct {
+		City, State string
+	}
+	type Result struct {
+		XMLName goxml.Name `xml:"Person"`
+		Name    string     `xml:"FullName"`
+		Phone   string
+		Email   []Email
+		Groups  []string `xml:"Group>Value"`
+		Address
+	}
+	v := Result{Name: "none", Phone: "none"}
+
+	data := `
+		<Person>
+			<FullName>Grace R. Emlin</FullName>
+			<Company>Example Inc.</Company>
+			<Email where="home">
+				<Addr>gre@example.com</Addr>
+			</Email>
+			<Email where='work'>
+				<Addr>gre@work.com</Addr>
+			</Email>
+			<Group>
+				<Value>Friends</Value>
+				<Value>Squash</Value>
+			</Group>
+			<City>Hanga Roa</City>
+			<State>Easter Island</State>
+		</Person>
+	`
+	err := goxml.Unmarshal([]byte(data), &v)
+	if err != nil {
+		fmt.Printf("error: %v", err)
+		return
+	}
+	fmt.Printf("XMLName: %#v\n", v.XMLName)
+	fmt.Printf("Name: %q\n", v.Name)
+	fmt.Printf("Phone: %q\n", v.Phone)
+	fmt.Printf("Email: %v\n", v.Email)
+	fmt.Printf("Groups: %v\n", v.Groups)
+	fmt.Printf("Address: %v\n", v.Address)
+	// Output:
+	// XMLName: goxml.Name{Space:"", Local:"Person"}
+	// Name: "Grace R. Emlin"
+	// Phone: "none"
+	// Email: [{home gre@example.com} {work gre@work.com}]
+	// Groups: [Friends Squash]
+	// Address: {Hanga Roa Easter Island}
+}

example_text_marshaling_test.go

@@ -0,0 +1,80 @@
+// Copyright 2018 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 goxml_test
+
+import (
+	"fmt"
+	"log"
+	"strings"
+
+	"git.pyer.club/kingecg/goxml"
+)
+
+type Size int
+
+const (
+	Unrecognized Size = iota
+	Small
+	Large
+)
+
+func (s *Size) UnmarshalText(text []byte) error {
+	switch strings.ToLower(string(text)) {
+	default:
+		*s = Unrecognized
+	case "small":
+		*s = Small
+	case "large":
+		*s = Large
+	}
+	return nil
+}
+
+func (s Size) MarshalText() ([]byte, error) {
+	var name string
+	switch s {
+	default:
+		name = "unrecognized"
+	case Small:
+		name = "small"
+	case Large:
+		name = "large"
+	}
+	return []byte(name), nil
+}
+
+func Example_textMarshalXML() {
+	blob := `
+	<sizes>
+		<size>small</size>
+		<size>regular</size>
+		<size>large</size>
+		<size>unrecognized</size>
+		<size>small</size>
+		<size>normal</size>
+		<size>small</size>
+		<size>large</size>
+	</sizes>`
+	var inventory struct {
+		Sizes []Size `xml:"size"`
+	}
+	if err := goxml.Unmarshal([]byte(blob), &inventory); err != nil {
+		log.Fatal(err)
+	}
+
+	counts := make(map[Size]int)
+	for _, size := range inventory.Sizes {
+		counts[size] += 1
+	}
+
+	fmt.Printf("Inventory Counts:\n* Small:        %d\n* Large:        %d\n* Unrecognized: %d\n",
+		counts[Small], counts[Large], counts[Unrecognized])
+
+	// Output:
+	// Inventory Counts:
+	// * Small:        3
+	// * Large:        2
+	// * Unrecognized: 3
+}

go.mod

@@ -0,0 +1,3 @@
+module git.pyer.club/kingecg/goxml
+
+go 1.23.1

prefix_test.go

@@ -0,0 +1,44 @@
+package goxml_test
+
+import (
+	"testing"
+
+	"git.pyer.club/kingecg/goxml"
+)
+
+type Person struct {
+	Name string `xml:"p:name"`
+	Age  int    `xml:"p:age"`
+}
+
+type Employee struct {
+	Person
+	Salary int `xml:"p:salary"`
+}
+
+func TestUnmarshal(t *testing.T) {
+	xml := `
+	<Employee>
+		<p:name>John Doe</p:name>
+		<p:age>42</p:age>
+		<p:salary>100000</p:salary>
+	</Employee>
+	`
+	e := Employee{}
+	err := goxml.Unmarshal([]byte(xml), &e)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestMashal(t *testing.T) {
+	e := Employee{
+		Person{
+			Name: "John",
+			Age:  30,
+		},
+		50000,
+	}
+	b, _ := goxml.Marshal(e)
+	t.Log(string(b))
+}

read.go

@@ -0,0 +1,777 @@
+// Copyright 2009 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 goxml
+
+import (
+	"bytes"
+	"encoding"
+	"errors"
+	"fmt"
+	"reflect"
+	"runtime"
+	"strconv"
+	"strings"
+)
+
+// BUG(rsc): Mapping between XML elements and data structures is inherently flawed:
+// an XML element is an order-dependent collection of anonymous
+// values, while a data structure is an order-independent collection
+// of named values.
+// See [encoding/json] for a textual representation more suitable
+// to data structures.
+
+// Unmarshal parses the XML-encoded data and stores the result in
+// the value pointed to by v, which must be an arbitrary struct,
+// slice, or string. Well-formed data that does not fit into v is
+// discarded.
+//
+// Because Unmarshal uses the reflect package, it can only assign
+// to exported (upper case) fields. Unmarshal uses a case-sensitive
+// comparison to match XML element names to tag values and struct
+// field names.
+//
+// Unmarshal maps an XML element to a struct using the following rules.
+// In the rules, the tag of a field refers to the value associated with the
+// key 'xml' in the struct field's tag (see the example above).
+//
+//   - If the struct has a field of type []byte or string with tag
+//     ",innerxml", Unmarshal accumulates the raw XML nested inside the
+//     element in that field. The rest of the rules still apply.
+//
+//   - If the struct has a field named XMLName of type Name,
+//     Unmarshal records the element name in that field.
+//
+//   - If the XMLName field has an associated tag of the form
+//     "name" or "namespace-URL name", the XML element must have
+//     the given name (and, optionally, name space) or else Unmarshal
+//     returns an error.
+//
+//   - If the XML element has an attribute whose name matches a
+//     struct field name with an associated tag containing ",attr" or
+//     the explicit name in a struct field tag of the form "name,attr",
+//     Unmarshal records the attribute value in that field.
+//
+//   - If the XML element has an attribute not handled by the previous
+//     rule and the struct has a field with an associated tag containing
+//     ",any,attr", Unmarshal records the attribute value in the first
+//     such field.
+//
+//   - If the XML element contains character data, that data is
+//     accumulated in the first struct field that has tag ",chardata".
+//     The struct field may have type []byte or string.
+//     If there is no such field, the character data is discarded.
+//
+//   - If the XML element contains comments, they are accumulated in
+//     the first struct field that has tag ",comment".  The struct
+//     field may have type []byte or string. If there is no such
+//     field, the comments are discarded.
+//
+//   - If the XML element contains a sub-element whose name matches
+//     the prefix of a tag formatted as "a" or "a>b>c", unmarshal
+//     will descend into the XML structure looking for elements with the
+//     given names, and will map the innermost elements to that struct
+//     field. A tag starting with ">" is equivalent to one starting
+//     with the field name followed by ">".
+//
+//   - If the XML element contains a sub-element whose name matches
+//     a struct field's XMLName tag and the struct field has no
+//     explicit name tag as per the previous rule, unmarshal maps
+//     the sub-element to that struct field.
+//
+//   - If the XML element contains a sub-element whose name matches a
+//     field without any mode flags (",attr", ",chardata", etc), Unmarshal
+//     maps the sub-element to that struct field.
+//
+//   - If the XML element contains a sub-element that hasn't matched any
+//     of the above rules and the struct has a field with tag ",any",
+//     unmarshal maps the sub-element to that struct field.
+//
+//   - An anonymous struct field is handled as if the fields of its
+//     value were part of the outer struct.
+//
+//   - A struct field with tag "-" is never unmarshaled into.
+//
+// If Unmarshal encounters a field type that implements the Unmarshaler
+// interface, Unmarshal calls its UnmarshalXML method to produce the value from
+// the XML element.  Otherwise, if the value implements
+// [encoding.TextUnmarshaler], Unmarshal calls that value's UnmarshalText method.
+//
+// Unmarshal maps an XML element to a string or []byte by saving the
+// concatenation of that element's character data in the string or
+// []byte. The saved []byte is never nil.
+//
+// Unmarshal maps an attribute value to a string or []byte by saving
+// the value in the string or slice.
+//
+// Unmarshal maps an attribute value to an [Attr] by saving the attribute,
+// including its name, in the Attr.
+//
+// Unmarshal maps an XML element or attribute value to a slice by
+// extending the length of the slice and mapping the element or attribute
+// to the newly created value.
+//
+// Unmarshal maps an XML element or attribute value to a bool by
+// setting it to the boolean value represented by the string. Whitespace
+// is trimmed and ignored.
+//
+// Unmarshal maps an XML element or attribute value to an integer or
+// floating-point field by setting the field to the result of
+// interpreting the string value in decimal. There is no check for
+// overflow. Whitespace is trimmed and ignored.
+//
+// Unmarshal maps an XML element to a Name by recording the element
+// name.
+//
+// Unmarshal maps an XML element to a pointer by setting the pointer
+// to a freshly allocated value and then mapping the element to that value.
+//
+// A missing element or empty attribute value will be unmarshaled as a zero value.
+// If the field is a slice, a zero value will be appended to the field. Otherwise, the
+// field will be set to its zero value.
+func Unmarshal(data []byte, v any) error {
+	return NewDecoder(bytes.NewReader(data)).Decode(v)
+}
+
+// Decode works like [Unmarshal], except it reads the decoder
+// stream to find the start element.
+func (d *Decoder) Decode(v any) error {
+	return d.DecodeElement(v, nil)
+}
+
+// DecodeElement works like [Unmarshal] except that it takes
+// a pointer to the start XML element to decode into v.
+// It is useful when a client reads some raw XML tokens itself
+// but also wants to defer to [Unmarshal] for some elements.
+func (d *Decoder) DecodeElement(v any, start *StartElement) error {
+	val := reflect.ValueOf(v)
+	if val.Kind() != reflect.Pointer {
+		return errors.New("non-pointer passed to Unmarshal")
+	}
+
+	if val.IsNil() {
+		return errors.New("nil pointer passed to Unmarshal")
+	}
+	return d.unmarshal(val.Elem(), start, 0)
+}
+
+// An UnmarshalError represents an error in the unmarshaling process.
+type UnmarshalError string
+
+func (e UnmarshalError) Error() string { return string(e) }
+
+// Unmarshaler is the interface implemented by objects that can unmarshal
+// an XML element description of themselves.
+//
+// UnmarshalXML decodes a single XML element
+// beginning with the given start element.
+// If it returns an error, the outer call to Unmarshal stops and
+// returns that error.
+// UnmarshalXML must consume exactly one XML element.
+// One common implementation strategy is to unmarshal into
+// a separate value with a layout matching the expected XML
+// using d.DecodeElement, and then to copy the data from
+// that value into the receiver.
+// Another common strategy is to use d.Token to process the
+// XML object one token at a time.
+// UnmarshalXML may not use d.RawToken.
+type Unmarshaler interface {
+	UnmarshalXML(d *Decoder, start StartElement) error
+}
+
+// UnmarshalerAttr is the interface implemented by objects that can unmarshal
+// an XML attribute description of themselves.
+//
+// UnmarshalXMLAttr decodes a single XML attribute.
+// If it returns an error, the outer call to [Unmarshal] stops and
+// returns that error.
+// UnmarshalXMLAttr is used only for struct fields with the
+// "attr" option in the field tag.
+type UnmarshalerAttr interface {
+	UnmarshalXMLAttr(attr Attr) error
+}
+
+// receiverType returns the receiver type to use in an expression like "%s.MethodName".
+func receiverType(val any) string {
+	t := reflect.TypeOf(val)
+	if t.Name() != "" {
+		return t.String()
+	}
+	return "(" + t.String() + ")"
+}
+
+// unmarshalInterface unmarshals a single XML element into val.
+// start is the opening tag of the element.
+func (d *Decoder) unmarshalInterface(val Unmarshaler, start *StartElement) error {
+	// Record that decoder must stop at end tag corresponding to start.
+	d.pushEOF()
+
+	d.unmarshalDepth++
+	err := val.UnmarshalXML(d, *start)
+	d.unmarshalDepth--
+	if err != nil {
+		d.popEOF()
+		return err
+	}
+
+	if !d.popEOF() {
+		return fmt.Errorf("xml: %s.UnmarshalXML did not consume entire <%s> element", receiverType(val), start.Name.Local)
+	}
+
+	return nil
+}
+
+// unmarshalTextInterface unmarshals a single XML element into val.
+// The chardata contained in the element (but not its children)
+// is passed to the text unmarshaler.
+func (d *Decoder) unmarshalTextInterface(val encoding.TextUnmarshaler) error {
+	var buf []byte
+	depth := 1
+	for depth > 0 {
+		t, err := d.Token()
+		if err != nil {
+			return err
+		}
+		switch t := t.(type) {
+		case CharData:
+			if depth == 1 {
+				buf = append(buf, t...)
+			}
+		case StartElement:
+			depth++
+		case EndElement:
+			depth--
+		}
+	}
+	return val.UnmarshalText(buf)
+}
+
+// unmarshalAttr unmarshals a single XML attribute into val.
+func (d *Decoder) unmarshalAttr(val reflect.Value, attr Attr) error {
+	if val.Kind() == reflect.Pointer {
+		if val.IsNil() {
+			val.Set(reflect.New(val.Type().Elem()))
+		}
+		val = val.Elem()
+	}
+	if val.CanInterface() && val.Type().Implements(unmarshalerAttrType) {
+		// This is an unmarshaler with a non-pointer receiver,
+		// so it's likely to be incorrect, but we do what we're told.
+		return val.Interface().(UnmarshalerAttr).UnmarshalXMLAttr(attr)
+	}
+	if val.CanAddr() {
+		pv := val.Addr()
+		if pv.CanInterface() && pv.Type().Implements(unmarshalerAttrType) {
+			return pv.Interface().(UnmarshalerAttr).UnmarshalXMLAttr(attr)
+		}
+	}
+
+	// Not an UnmarshalerAttr; try encoding.TextUnmarshaler.
+	if val.CanInterface() && val.Type().Implements(textUnmarshalerType) {
+		// This is an unmarshaler with a non-pointer receiver,
+		// so it's likely to be incorrect, but we do what we're told.
+		return val.Interface().(encoding.TextUnmarshaler).UnmarshalText([]byte(attr.Value))
+	}
+	if val.CanAddr() {
+		pv := val.Addr()
+		if pv.CanInterface() && pv.Type().Implements(textUnmarshalerType) {
+			return pv.Interface().(encoding.TextUnmarshaler).UnmarshalText([]byte(attr.Value))
+		}
+	}
+
+	if val.Type().Kind() == reflect.Slice && val.Type().Elem().Kind() != reflect.Uint8 {
+		// Slice of element values.
+		// Grow slice.
+		n := val.Len()
+		val.Grow(1)
+		val.SetLen(n + 1)
+
+		// Recur to read element into slice.
+		if err := d.unmarshalAttr(val.Index(n), attr); err != nil {
+			val.SetLen(n)
+			return err
+		}
+		return nil
+	}
+
+	if val.Type() == attrType {
+		val.Set(reflect.ValueOf(attr))
+		return nil
+	}
+
+	return copyValue(val, []byte(attr.Value))
+}
+
+var (
+	attrType            = reflect.TypeFor[Attr]()
+	unmarshalerType     = reflect.TypeFor[Unmarshaler]()
+	unmarshalerAttrType = reflect.TypeFor[UnmarshalerAttr]()
+	textUnmarshalerType = reflect.TypeFor[encoding.TextUnmarshaler]()
+)
+
+const (
+	maxUnmarshalDepth     = 10000
+	maxUnmarshalDepthWasm = 5000 // go.dev/issue/56498
+)
+
+var errUnmarshalDepth = errors.New("exceeded max depth")
+
+// Unmarshal a single XML element into val.
+func (d *Decoder) unmarshal(val reflect.Value, start *StartElement, depth int) error {
+	if depth >= maxUnmarshalDepth || runtime.GOARCH == "wasm" && depth >= maxUnmarshalDepthWasm {
+		return errUnmarshalDepth
+	}
+	// Find start element if we need it.
+	if start == nil {
+		for {
+			tok, err := d.Token()
+			if err != nil {
+				return err
+			}
+			if t, ok := tok.(StartElement); ok {
+				start = &t
+				break
+			}
+		}
+	}
+
+	// Load value from interface, but only if the result will be
+	// usefully addressable.
+	if val.Kind() == reflect.Interface && !val.IsNil() {
+		e := val.Elem()
+		if e.Kind() == reflect.Pointer && !e.IsNil() {
+			val = e
+		}
+	}
+
+	if val.Kind() == reflect.Pointer {
+		if val.IsNil() {
+			val.Set(reflect.New(val.Type().Elem()))
+		}
+		val = val.Elem()
+	}
+
+	if val.CanInterface() && val.Type().Implements(unmarshalerType) {
+		// This is an unmarshaler with a non-pointer receiver,
+		// so it's likely to be incorrect, but we do what we're told.
+		return d.unmarshalInterface(val.Interface().(Unmarshaler), start)
+	}
+
+	if val.CanAddr() {
+		pv := val.Addr()
+		if pv.CanInterface() && pv.Type().Implements(unmarshalerType) {
+			return d.unmarshalInterface(pv.Interface().(Unmarshaler), start)
+		}
+	}
+
+	if val.CanInterface() && val.Type().Implements(textUnmarshalerType) {
+		return d.unmarshalTextInterface(val.Interface().(encoding.TextUnmarshaler))
+	}
+
+	if val.CanAddr() {
+		pv := val.Addr()
+		if pv.CanInterface() && pv.Type().Implements(textUnmarshalerType) {
+			return d.unmarshalTextInterface(pv.Interface().(encoding.TextUnmarshaler))
+		}
+	}
+
+	var (
+		data         []byte
+		saveData     reflect.Value
+		comment      []byte
+		saveComment  reflect.Value
+		saveXML      reflect.Value
+		saveXMLIndex int
+		saveXMLData  []byte
+		saveAny      reflect.Value
+		sv           reflect.Value
+		tinfo        *typeInfo
+		err          error
+	)
+
+	switch v := val; v.Kind() {
+	default:
+		return errors.New("unknown type " + v.Type().String())
+
+	case reflect.Interface:
+		// TODO: For now, simply ignore the field. In the near
+		//       future we may choose to unmarshal the start
+		//       element on it, if not nil.
+		return d.Skip()
+
+	case reflect.Slice:
+		typ := v.Type()
+		if typ.Elem().Kind() == reflect.Uint8 {
+			// []byte
+			saveData = v
+			break
+		}
+
+		// Slice of element values.
+		// Grow slice.
+		n := v.Len()
+		v.Grow(1)
+		v.SetLen(n + 1)
+
+		// Recur to read element into slice.
+		if err := d.unmarshal(v.Index(n), start, depth+1); err != nil {
+			v.SetLen(n)
+			return err
+		}
+		return nil
+
+	case reflect.Bool, reflect.Float32, reflect.Float64, reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr, reflect.String:
+		saveData = v
+
+	case reflect.Struct:
+		typ := v.Type()
+		if typ == nameType {
+			v.Set(reflect.ValueOf(start.Name))
+			break
+		}
+
+		sv = v
+		tinfo, err = getTypeInfo(typ, true)
+		if err != nil {
+			return err
+		}
+
+		// Validate and assign element name.
+		if tinfo.xmlname != nil {
+			finfo := tinfo.xmlname
+			if finfo.name != "" && finfo.name != start.Name.Local {
+				return UnmarshalError("expected element type <" + finfo.name + "> but have <" + start.Name.Local + ">")
+			}
+			if finfo.xmlns != "" && finfo.xmlns != start.Name.Space {
+				e := "expected element <" + finfo.name + "> in name space " + finfo.xmlns + " but have "
+				if start.Name.Space == "" {
+					e += "no name space"
+				} else {
+					e += start.Name.Space
+				}
+				return UnmarshalError(e)
+			}
+			fv := finfo.value(sv, initNilPointers)
+			if _, ok := fv.Interface().(Name); ok {
+				fv.Set(reflect.ValueOf(start.Name))
+			}
+		}
+
+		// Assign attributes.
+		for _, a := range start.Attr {
+			handled := false
+			any := -1
+			for i := range tinfo.fields {
+				finfo := &tinfo.fields[i]
+				switch finfo.flags & fMode {
+				case fAttr:
+					strv := finfo.value(sv, initNilPointers)
+					if a.Name.Local == finfo.name && (finfo.xmlns == "" || finfo.xmlns == a.Name.Space) {
+						if err := d.unmarshalAttr(strv, a); err != nil {
+							return err
+						}
+						handled = true
+					}
+
+				case fAny | fAttr:
+					if any == -1 {
+						any = i
+					}
+				}
+			}
+			if !handled && any >= 0 {
+				finfo := &tinfo.fields[any]
+				strv := finfo.value(sv, initNilPointers)
+				if err := d.unmarshalAttr(strv, a); err != nil {
+					return err
+				}
+			}
+		}
+
+		// Determine whether we need to save character data or comments.
+		for i := range tinfo.fields {
+			finfo := &tinfo.fields[i]
+			switch finfo.flags & fMode {
+			case fCDATA, fCharData:
+				if !saveData.IsValid() {
+					saveData = finfo.value(sv, initNilPointers)
+				}
+
+			case fComment:
+				if !saveComment.IsValid() {
+					saveComment = finfo.value(sv, initNilPointers)
+				}
+
+			case fAny, fAny | fElement:
+				if !saveAny.IsValid() {
+					saveAny = finfo.value(sv, initNilPointers)
+				}
+
+			case fInnerXML:
+				if !saveXML.IsValid() {
+					saveXML = finfo.value(sv, initNilPointers)
+					if d.saved == nil {
+						saveXMLIndex = 0
+						d.saved = new(bytes.Buffer)
+					} else {
+						saveXMLIndex = d.savedOffset()
+					}
+				}
+			}
+		}
+	}
+
+	// Find end element.
+	// Process sub-elements along the way.
+Loop:
+	for {
+		var savedOffset int
+		if saveXML.IsValid() {
+			savedOffset = d.savedOffset()
+		}
+		tok, err := d.Token()
+		if err != nil {
+			return err
+		}
+		switch t := tok.(type) {
+		case StartElement:
+			consumed := false
+			if sv.IsValid() {
+				// unmarshalPath can call unmarshal, so we need to pass the depth through so that
+				// we can continue to enforce the maximum recursion limit.
+				consumed, err = d.unmarshalPath(tinfo, sv, nil, &t, depth)
+				if err != nil {
+					return err
+				}
+				if !consumed && saveAny.IsValid() {
+					consumed = true
+					if err := d.unmarshal(saveAny, &t, depth+1); err != nil {
+						return err
+					}
+				}
+			}
+			if !consumed {
+				if err := d.Skip(); err != nil {
+					return err
+				}
+			}
+
+		case EndElement:
+			if saveXML.IsValid() {
+				saveXMLData = d.saved.Bytes()[saveXMLIndex:savedOffset]
+				if saveXMLIndex == 0 {
+					d.saved = nil
+				}
+			}
+			break Loop
+
+		case CharData:
+			if saveData.IsValid() {
+				data = append(data, t...)
+			}
+
+		case Comment:
+			if saveComment.IsValid() {
+				comment = append(comment, t...)
+			}
+		}
+	}
+
+	if saveData.IsValid() && saveData.CanInterface() && saveData.Type().Implements(textUnmarshalerType) {
+		if err := saveData.Interface().(encoding.TextUnmarshaler).UnmarshalText(data); err != nil {
+			return err
+		}
+		saveData = reflect.Value{}
+	}
+
+	if saveData.IsValid() && saveData.CanAddr() {
+		pv := saveData.Addr()
+		if pv.CanInterface() && pv.Type().Implements(textUnmarshalerType) {
+			if err := pv.Interface().(encoding.TextUnmarshaler).UnmarshalText(data); err != nil {
+				return err
+			}
+			saveData = reflect.Value{}
+		}
+	}
+
+	if err := copyValue(saveData, data); err != nil {
+		return err
+	}
+
+	switch t := saveComment; t.Kind() {
+	case reflect.String:
+		t.SetString(string(comment))
+	case reflect.Slice:
+		t.Set(reflect.ValueOf(comment))
+	}
+
+	switch t := saveXML; t.Kind() {
+	case reflect.String:
+		t.SetString(string(saveXMLData))
+	case reflect.Slice:
+		if t.Type().Elem().Kind() == reflect.Uint8 {
+			t.Set(reflect.ValueOf(saveXMLData))
+		}
+	}
+
+	return nil
+}
+
+func copyValue(dst reflect.Value, src []byte) (err error) {
+	dst0 := dst
+
+	if dst.Kind() == reflect.Pointer {
+		if dst.IsNil() {
+			dst.Set(reflect.New(dst.Type().Elem()))
+		}
+		dst = dst.Elem()
+	}
+
+	// Save accumulated data.
+	switch dst.Kind() {
+	case reflect.Invalid:
+		// Probably a comment.
+	default:
+		return errors.New("cannot unmarshal into " + dst0.Type().String())
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		if len(src) == 0 {
+			dst.SetInt(0)
+			return nil
+		}
+		itmp, err := strconv.ParseInt(strings.TrimSpace(string(src)), 10, dst.Type().Bits())
+		if err != nil {
+			return err
+		}
+		dst.SetInt(itmp)
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		if len(src) == 0 {
+			dst.SetUint(0)
+			return nil
+		}
+		utmp, err := strconv.ParseUint(strings.TrimSpace(string(src)), 10, dst.Type().Bits())
+		if err != nil {
+			return err
+		}
+		dst.SetUint(utmp)
+	case reflect.Float32, reflect.Float64:
+		if len(src) == 0 {
+			dst.SetFloat(0)
+			return nil
+		}
+		ftmp, err := strconv.ParseFloat(strings.TrimSpace(string(src)), dst.Type().Bits())
+		if err != nil {
+			return err
+		}
+		dst.SetFloat(ftmp)
+	case reflect.Bool:
+		if len(src) == 0 {
+			dst.SetBool(false)
+			return nil
+		}
+		value, err := strconv.ParseBool(strings.TrimSpace(string(src)))
+		if err != nil {
+			return err
+		}
+		dst.SetBool(value)
+	case reflect.String:
+		dst.SetString(string(src))
+	case reflect.Slice:
+		if len(src) == 0 {
+			// non-nil to flag presence
+			src = []byte{}
+		}
+		dst.SetBytes(src)
+	}
+	return nil
+}
+
+// unmarshalPath walks down an XML structure looking for wanted
+// paths, and calls unmarshal on them.
+// The consumed result tells whether XML elements have been consumed
+// from the Decoder until start's matching end element, or if it's
+// still untouched because start is uninteresting for sv's fields.
+func (d *Decoder) unmarshalPath(tinfo *typeInfo, sv reflect.Value, parents []string, start *StartElement, depth int) (consumed bool, err error) {
+	recurse := false
+Loop:
+	for i := range tinfo.fields {
+		finfo := &tinfo.fields[i]
+		if finfo.flags&fElement == 0 || len(finfo.parents) < len(parents) || finfo.xmlns != "" && finfo.xmlns != start.Name.Space {
+			continue
+		}
+		for j := range parents {
+			if parents[j] != finfo.parents[j] {
+				continue Loop
+			}
+		}
+		if len(finfo.parents) == len(parents) && finfo.name == start.Name.Local {
+			// It's a perfect match, unmarshal the field.
+			return true, d.unmarshal(finfo.value(sv, initNilPointers), start, depth+1)
+		}
+		if len(finfo.parents) > len(parents) && finfo.parents[len(parents)] == start.Name.Local {
+			// It's a prefix for the field. Break and recurse
+			// since it's not ok for one field path to be itself
+			// the prefix for another field path.
+			recurse = true
+
+			// We can reuse the same slice as long as we
+			// don't try to append to it.
+			parents = finfo.parents[:len(parents)+1]
+			break
+		}
+	}
+	if !recurse {
+		// We have no business with this element.
+		return false, nil
+	}
+	// The element is not a perfect match for any field, but one
+	// or more fields have the path to this element as a parent
+	// prefix. Recurse and attempt to match these.
+	for {
+		var tok Token
+		tok, err = d.Token()
+		if err != nil {
+			return true, err
+		}
+		switch t := tok.(type) {
+		case StartElement:
+			// the recursion depth of unmarshalPath is limited to the path length specified
+			// by the struct field tag, so we don't increment the depth here.
+			consumed2, err := d.unmarshalPath(tinfo, sv, parents, &t, depth)
+			if err != nil {
+				return true, err
+			}
+			if !consumed2 {
+				if err := d.Skip(); err != nil {
+					return true, err
+				}
+			}
+		case EndElement:
+			return true, nil
+		}
+	}
+}
+
+// Skip reads tokens until it has consumed the end element
+// matching the most recent start element already consumed,
+// skipping nested structures.
+// It returns nil if it finds an end element matching the start
+// element; otherwise it returns an error describing the problem.
+func (d *Decoder) Skip() error {
+	var depth int64
+	for {
+		tok, err := d.Token()
+		if err != nil {
+			return err
+		}
+		switch tok.(type) {
+		case StartElement:
+			depth++
+		case EndElement:
+			if depth == 0 {
+				return nil
+			}
+			depth--
+		}
+	}
+}

typeinfo.go

@@ -0,0 +1,372 @@
+// Copyright 2011 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 goxml
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+	"sync"
+)
+
+// typeInfo holds details for the xml representation of a type.
+type typeInfo struct {
+	xmlname *fieldInfo
+	fields  []fieldInfo
+}
+
+// fieldInfo holds details for the xml representation of a single field.
+type fieldInfo struct {
+	idx     []int
+	name    string
+	xmlns   string
+	flags   fieldFlags
+	parents []string
+}
+
+type fieldFlags int
+
+const (
+	fElement fieldFlags = 1 << iota
+	fAttr
+	fCDATA
+	fCharData
+	fInnerXML
+	fComment
+	fAny
+
+	fOmitEmpty
+
+	fMode = fElement | fAttr | fCDATA | fCharData | fInnerXML | fComment | fAny
+
+	xmlName = "XMLName"
+)
+
+var tinfoMap sync.Map // map[reflect.Type]*typeInfo
+
+var nameType = reflect.TypeFor[Name]()
+
+// getTypeInfo returns the typeInfo structure with details necessary
+// for marshaling and unmarshaling typ.
+func getTypeInfo(typ reflect.Type, inDecode bool) (*typeInfo, error) {
+	if ti, ok := tinfoMap.Load(typ); ok {
+		return ti.(*typeInfo), nil
+	}
+
+	tinfo := &typeInfo{}
+	if typ.Kind() == reflect.Struct && typ != nameType {
+		n := typ.NumField()
+		for i := 0; i < n; i++ {
+			f := typ.Field(i)
+			if (!f.IsExported() && !f.Anonymous) || f.Tag.Get("xml") == "-" {
+				continue // Private field
+			}
+
+			// For embedded structs, embed its fields.
+			if f.Anonymous {
+				t := f.Type
+				if t.Kind() == reflect.Pointer {
+					t = t.Elem()
+				}
+				if t.Kind() == reflect.Struct {
+					inner, err := getTypeInfo(t, inDecode)
+					if err != nil {
+						return nil, err
+					}
+					if tinfo.xmlname == nil {
+						tinfo.xmlname = inner.xmlname
+					}
+					for _, finfo := range inner.fields {
+						finfo.idx = append([]int{i}, finfo.idx...)
+						if err := addFieldInfo(typ, tinfo, &finfo); err != nil {
+							return nil, err
+						}
+					}
+					continue
+				}
+			}
+
+			finfo, err := structFieldInfo(typ, &f, inDecode)
+			if err != nil {
+				return nil, err
+			}
+
+			if f.Name == xmlName {
+				tinfo.xmlname = finfo
+				continue
+			}
+
+			// Add the field if it doesn't conflict with other fields.
+			if err := addFieldInfo(typ, tinfo, finfo); err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	ti, _ := tinfoMap.LoadOrStore(typ, tinfo)
+	return ti.(*typeInfo), nil
+}
+
+// structFieldInfo builds and returns a fieldInfo for f.
+func structFieldInfo(typ reflect.Type, f *reflect.StructField, inDecode bool) (*fieldInfo, error) {
+	finfo := &fieldInfo{idx: f.Index}
+
+	// Split the tag from the xml namespace if necessary.
+	tag := f.Tag.Get("xml")
+	if ns, t, ok := strings.Cut(tag, " "); ok {
+		finfo.xmlns, tag = ns, t
+	}
+	if inDecode {
+		if ns, t, ok := strings.Cut(tag, ":"); ok {
+			finfo.xmlns, tag = ns, t
+		}
+	}
+
+	// Parse flags.
+	tokens := strings.Split(tag, ",")
+	if len(tokens) == 1 {
+		finfo.flags = fElement
+	} else {
+		tag = tokens[0]
+		for _, flag := range tokens[1:] {
+			switch flag {
+			case "attr":
+				finfo.flags |= fAttr
+			case "cdata":
+				finfo.flags |= fCDATA
+			case "chardata":
+				finfo.flags |= fCharData
+			case "innerxml":
+				finfo.flags |= fInnerXML
+			case "comment":
+				finfo.flags |= fComment
+			case "any":
+				finfo.flags |= fAny
+			case "omitempty":
+				finfo.flags |= fOmitEmpty
+			}
+		}
+
+		// Validate the flags used.
+		valid := true
+		switch mode := finfo.flags & fMode; mode {
+		case 0:
+			finfo.flags |= fElement
+		case fAttr, fCDATA, fCharData, fInnerXML, fComment, fAny, fAny | fAttr:
+			if f.Name == xmlName || tag != "" && mode != fAttr {
+				valid = false
+			}
+		default:
+			// This will also catch multiple modes in a single field.
+			valid = false
+		}
+		if finfo.flags&fMode == fAny {
+			finfo.flags |= fElement
+		}
+		if finfo.flags&fOmitEmpty != 0 && finfo.flags&(fElement|fAttr) == 0 {
+			valid = false
+		}
+		if !valid {
+			return nil, fmt.Errorf("xml: invalid tag in field %s of type %s: %q",
+				f.Name, typ, f.Tag.Get("xml"))
+		}
+	}
+
+	// Use of xmlns without a name is not allowed.
+	if finfo.xmlns != "" && tag == "" {
+		return nil, fmt.Errorf("xml: namespace without name in field %s of type %s: %q",
+			f.Name, typ, f.Tag.Get("xml"))
+	}
+
+	if f.Name == xmlName {
+		// The XMLName field records the XML element name. Don't
+		// process it as usual because its name should default to
+		// empty rather than to the field name.
+		finfo.name = tag
+		return finfo, nil
+	}
+
+	if tag == "" {
+		// If the name part of the tag is completely empty, get
+		// default from XMLName of underlying struct if feasible,
+		// or field name otherwise.
+		if xmlname := lookupXMLName(f.Type, inDecode); xmlname != nil {
+			finfo.xmlns, finfo.name = xmlname.xmlns, xmlname.name
+		} else {
+			finfo.name = f.Name
+		}
+		return finfo, nil
+	}
+
+	// Prepare field name and parents.
+	parents := strings.Split(tag, ">")
+	if parents[0] == "" {
+		parents[0] = f.Name
+	}
+	if parents[len(parents)-1] == "" {
+		return nil, fmt.Errorf("xml: trailing '>' in field %s of type %s", f.Name, typ)
+	}
+	finfo.name = parents[len(parents)-1]
+	if len(parents) > 1 {
+		if (finfo.flags & fElement) == 0 {
+			return nil, fmt.Errorf("xml: %s chain not valid with %s flag", tag, strings.Join(tokens[1:], ","))
+		}
+		finfo.parents = parents[:len(parents)-1]
+	}
+
+	// If the field type has an XMLName field, the names must match
+	// so that the behavior of both marshaling and unmarshaling
+	// is straightforward and unambiguous.
+	if finfo.flags&fElement != 0 {
+		ftyp := f.Type
+		xmlname := lookupXMLName(ftyp, inDecode)
+		if xmlname != nil && xmlname.name != finfo.name {
+			return nil, fmt.Errorf("xml: name %q in tag of %s.%s conflicts with name %q in %s.XMLName",
+				finfo.name, typ, f.Name, xmlname.name, ftyp)
+		}
+	}
+	return finfo, nil
+}
+
+// lookupXMLName returns the fieldInfo for typ's XMLName field
+// in case it exists and has a valid xml field tag, otherwise
+// it returns nil.
+func lookupXMLName(typ reflect.Type, inDecode bool) (xmlname *fieldInfo) {
+	for typ.Kind() == reflect.Pointer {
+		typ = typ.Elem()
+	}
+	if typ.Kind() != reflect.Struct {
+		return nil
+	}
+	for i, n := 0, typ.NumField(); i < n; i++ {
+		f := typ.Field(i)
+		if f.Name != xmlName {
+			continue
+		}
+		finfo, err := structFieldInfo(typ, &f, inDecode)
+		if err == nil && finfo.name != "" {
+			return finfo
+		}
+		// Also consider errors as a non-existent field tag
+		// and let getTypeInfo itself report the error.
+		break
+	}
+	return nil
+}
+
+// addFieldInfo adds finfo to tinfo.fields if there are no
+// conflicts, or if conflicts arise from previous fields that were
+// obtained from deeper embedded structures than finfo. In the latter
+// case, the conflicting entries are dropped.
+// A conflict occurs when the path (parent + name) to a field is
+// itself a prefix of another path, or when two paths match exactly.
+// It is okay for field paths to share a common, shorter prefix.
+func addFieldInfo(typ reflect.Type, tinfo *typeInfo, newf *fieldInfo) error {
+	var conflicts []int
+Loop:
+	// First, figure all conflicts. Most working code will have none.
+	for i := range tinfo.fields {
+		oldf := &tinfo.fields[i]
+		if oldf.flags&fMode != newf.flags&fMode {
+			continue
+		}
+		if oldf.xmlns != "" && newf.xmlns != "" && oldf.xmlns != newf.xmlns {
+			continue
+		}
+		minl := min(len(newf.parents), len(oldf.parents))
+		for p := 0; p < minl; p++ {
+			if oldf.parents[p] != newf.parents[p] {
+				continue Loop
+			}
+		}
+		if len(oldf.parents) > len(newf.parents) {
+			if oldf.parents[len(newf.parents)] == newf.name {
+				conflicts = append(conflicts, i)
+			}
+		} else if len(oldf.parents) < len(newf.parents) {
+			if newf.parents[len(oldf.parents)] == oldf.name {
+				conflicts = append(conflicts, i)
+			}
+		} else {
+			if newf.name == oldf.name && newf.xmlns == oldf.xmlns {
+				conflicts = append(conflicts, i)
+			}
+		}
+	}
+	// Without conflicts, add the new field and return.
+	if conflicts == nil {
+		tinfo.fields = append(tinfo.fields, *newf)
+		return nil
+	}
+
+	// If any conflict is shallower, ignore the new field.
+	// This matches the Go field resolution on embedding.
+	for _, i := range conflicts {
+		if len(tinfo.fields[i].idx) < len(newf.idx) {
+			return nil
+		}
+	}
+
+	// Otherwise, if any of them is at the same depth level, it's an error.
+	for _, i := range conflicts {
+		oldf := &tinfo.fields[i]
+		if len(oldf.idx) == len(newf.idx) {
+			f1 := typ.FieldByIndex(oldf.idx)
+			f2 := typ.FieldByIndex(newf.idx)
+			return &TagPathError{typ, f1.Name, f1.Tag.Get("xml"), f2.Name, f2.Tag.Get("xml")}
+		}
+	}
+
+	// Otherwise, the new field is shallower, and thus takes precedence,
+	// so drop the conflicting fields from tinfo and append the new one.
+	for c := len(conflicts) - 1; c >= 0; c-- {
+		i := conflicts[c]
+		copy(tinfo.fields[i:], tinfo.fields[i+1:])
+		tinfo.fields = tinfo.fields[:len(tinfo.fields)-1]
+	}
+	tinfo.fields = append(tinfo.fields, *newf)
+	return nil
+}
+
+// A TagPathError represents an error in the unmarshaling process
+// caused by the use of field tags with conflicting paths.
+type TagPathError struct {
+	Struct       reflect.Type
+	Field1, Tag1 string
+	Field2, Tag2 string
+}
+
+func (e *TagPathError) Error() string {
+	return fmt.Sprintf("%s field %q with tag %q conflicts with field %q with tag %q", e.Struct, e.Field1, e.Tag1, e.Field2, e.Tag2)
+}
+
+const (
+	initNilPointers     = true
+	dontInitNilPointers = false
+)
+
+// value returns v's field value corresponding to finfo.
+// It's equivalent to v.FieldByIndex(finfo.idx), but when passed
+// initNilPointers, it initializes and dereferences pointers as necessary.
+// When passed dontInitNilPointers and a nil pointer is reached, the function
+// returns a zero reflect.Value.
+func (finfo *fieldInfo) value(v reflect.Value, shouldInitNilPointers bool) reflect.Value {
+	for i, x := range finfo.idx {
+		if i > 0 {
+			t := v.Type()
+			if t.Kind() == reflect.Pointer && t.Elem().Kind() == reflect.Struct {
+				if v.IsNil() {
+					if !shouldInitNilPointers {
+						return reflect.Value{}
+					}
+					v.Set(reflect.New(v.Type().Elem()))
+				}
+				v = v.Elem()
+			}
+		}
+		v = v.Field(x)
+	}
+	return v
+}