reflect: add FieldByNameFunc

xml: add support for XML marshalling embedded structs.

R=rsc
CC=golang-dev
https://golang.org/cl/837042

src/pkg/reflect/type.go

@@ -507,7 +507,7 @@ func (t *StructType) FieldByIndex(index []int) (f StructField) {
 
 const inf = 1 << 30 // infinity - no struct has that many nesting levels
 
-func (t *StructType) fieldByName(name string, mark map[*StructType]bool, depth int) (ff StructField, fd int) {
+func (t *StructType) fieldByNameFunc(match func(string) bool, mark map[*StructType]bool, depth int) (ff StructField, fd int) {
 	fd = inf // field depth
 
 	if mark[t] {
@@ -522,7 +522,7 @@ L: for i, _ := range t.fields {
 		f := t.Field(i)
 		d := inf
 		switch {
-		case f.Name == name:
+		case match(f.Name):
 			// Matching top-level field.
 			d = depth
 		case f.Anonymous:
@@ -531,13 +531,13 @@ L: for i, _ := range t.fields {
 				ft = pt.Elem()
 			}
 			switch {
-			case ft.Name() == name:
+			case match(ft.Name()):
 				// Matching anonymous top-level field.
 				d = depth
 			case fd > depth:
 				// No top-level field yet; look inside nested structs.
 				if st, ok := ft.(*StructType); ok {
-					f, d = st.fieldByName(name, mark, depth+1)
+					f, d = st.fieldByNameFunc(match, mark, depth+1)
 				}
 			}
 		}
@@ -576,7 +576,13 @@ L: for i, _ := range t.fields {
 // FieldByName returns the struct field with the given name
 // and a boolean to indicate if the field was found.
 func (t *StructType) FieldByName(name string) (f StructField, present bool) {
-	if ff, fd := t.fieldByName(name, make(map[*StructType]bool), 0); fd < inf {
+	return t.FieldByNameFunc(func(s string) bool { return s == name })
+}
+
+// FieldByNameFunc returns the struct field with a name that satisfies the
+// match function and a boolean to indicate if the field was found.
+func (t *StructType) FieldByNameFunc(match func(string) bool) (f StructField, present bool) {
+	if ff, fd := t.fieldByNameFunc(match, make(map[*StructType]bool), 0); fd < inf {
 		ff.Index = ff.Index[0 : fd+1]
 		f, present = ff, true
 	}

src/pkg/reflect/value.go

@@ -1251,6 +1251,16 @@ func (t *StructValue) FieldByName(name string) Value {
 	return nil
 }
 
+// FieldByNameFunc returns the struct field with a name that satisfies the
+// match function.
+// The result is nil if no field was found.
+func (t *StructValue) FieldByNameFunc(match func(string) bool) Value {
+	if f, ok := t.Type().(*StructType).FieldByNameFunc(match); ok {
+		return t.FieldByIndex(f.Index)
+	}
+	return nil
+}
+
 // NumField returns the number of fields in the struct.
 func (v *StructValue) NumField() int { return v.typ.(*StructType).NumField() }
 

src/pkg/xml/embed_test.go

@@ -0,0 +1,124 @@
+// Copyright 2010 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 xml
+
+import "testing"
+
+type C struct {
+	Name string
+	Open bool
+}
+
+type A struct {
+	XMLName Name "http://domain a"
+	C
+	B      B
+	FieldA string
+}
+
+type B struct {
+	XMLName Name "b"
+	C
+	FieldB string
+}
+
+const _1a = `
+<?xml version="1.0" encoding="UTF-8"?>
+<a xmlns="http://domain">
+  <name>KmlFile</name>
+  <open>1</open>
+  <b>
+    <name>Absolute</name>
+    <open>0</open>
+    <fieldb>bar</fieldb>
+  </b>
+  <fielda>foo</fielda>
+</a>
+`
+
+// Tests that embedded structs are marshalled.
+func TestEmbedded1(t *testing.T) {
+	var a A
+	if e := Unmarshal(StringReader(_1a), &a); e != nil {
+		t.Fatalf("Unmarshal: %s", e)
+	}
+	if a.FieldA != "foo" {
+		t.Fatalf("Unmarshal: expected 'foo' but found '%s'", a.FieldA)
+	}
+	if a.Name != "KmlFile" {
+		t.Fatalf("Unmarshal: expected 'KmlFile' but found '%s'", a.Name)
+	}
+	if !a.Open {
+		t.Fatal("Unmarshal: expected 'true' but found otherwise")
+	}
+	if a.B.FieldB != "bar" {
+		t.Fatalf("Unmarshal: expected 'bar' but found '%s'", a.B.FieldB)
+	}
+	if a.B.Name != "Absolute" {
+		t.Fatalf("Unmarshal: expected 'Absolute' but found '%s'", a.B.Name)
+	}
+	if a.B.Open {
+		t.Fatal("Unmarshal: expected 'false' but found otherwise")
+	}
+}
+
+type A2 struct {
+	XMLName Name "http://domain a"
+	XY      string
+	Xy      string
+}
+
+const _2a = `
+<?xml version="1.0" encoding="UTF-8"?>
+<a xmlns="http://domain">
+  <xy>foo</xy>
+</a>
+`
+
+// Tests that conflicting field names get excluded.
+func TestEmbedded2(t *testing.T) {
+	var a A2
+	if e := Unmarshal(StringReader(_2a), &a); e != nil {
+		t.Fatalf("Unmarshal: %s", e)
+	}
+	if a.XY != "" {
+		t.Fatalf("Unmarshal: expected empty string but found '%s'", a.XY)
+	}
+	if a.Xy != "" {
+		t.Fatalf("Unmarshal: expected empty string but found '%s'", a.Xy)
+	}
+}
+
+type A3 struct {
+	XMLName Name "http://domain a"
+	xy      string
+}
+
+// Tests that private fields are not set.
+func TestEmbedded3(t *testing.T) {
+	var a A3
+	if e := Unmarshal(StringReader(_2a), &a); e != nil {
+		t.Fatalf("Unmarshal: %s", e)
+	}
+	if a.xy != "" {
+		t.Fatalf("Unmarshal: expected empty string but found '%s'", a.xy)
+	}
+}
+
+type A4 struct {
+	XMLName Name "http://domain a"
+	Any     string
+}
+
+// Tests that private fields are not set.
+func TestEmbedded4(t *testing.T) {
+	var a A4
+	if e := Unmarshal(StringReader(_2a), &a); e != nil {
+		t.Fatalf("Unmarshal: %s", e)
+	}
+	if a.Any != "foo" {
+		t.Fatalf("Unmarshal: expected 'foo' but found '%s'", a.Any)
+	}
+}

src/pkg/xml/read.go

@@ -12,6 +12,7 @@ import (
 	"strconv"
 	"strings"
 	"unicode"
+	"utf8"
 )
 
 // BUG(rsc): Mapping between XML elements and data structures is inherently flawed:
@@ -331,24 +332,24 @@ Loop:
 		case StartElement:
 			// Sub-element.
 			// Look up by tag name.
-			// If that fails, fall back to mop-up field named "Any".
 			if sv != nil {
 				k := fieldName(t.Name.Local)
-				any := -1
-				for i, n := 0, styp.NumField(); i < n; i++ {
-					f := styp.Field(i)
-					if strings.ToLower(f.Name) == k {
-						if err := p.unmarshal(sv.FieldByIndex(f.Index), &t); err != nil {
-							return err
-						}
-						continue Loop
-					}
-					if any < 0 && f.Name == "Any" {
-						any = i
+				match := func(s string) bool {
+					// check if the name matches ignoring case
+					if strings.ToLower(s) != strings.ToLower(k) {
+						return false
 					}
+					// now check that it's public
+					c, _ := utf8.DecodeRuneInString(s)
+					return unicode.IsUpper(c)
 				}
-				if any >= 0 {
-					if err := p.unmarshal(sv.FieldByIndex(styp.Field(any).Index), &t); err != nil {
+
+				f, found := styp.FieldByNameFunc(match)
+				if !found { // fall back to mop-up field named "Any"
+					f, found = styp.FieldByName("Any")
+				}
+				if found {
+					if err := p.unmarshal(sv.FieldByIndex(f.Index), &t); err != nil {
 						return err
 					}
 					continue Loop