- FieldByName lookup through anonymous fields

- FieldByIndex
- changed StructField.Index type from int -> []int
- adjustments to reflect clients

R=rsc,r
DELTA=336  (263 added, 47 deleted, 26 changed)
OCL=32731
CL=32802

src/pkg/datafmt/datafmt.go

@@ -410,49 +410,6 @@ func (s *State) error(msg string) {
 }
 
 
-// getField searches in val, which must be a struct, for a field
-// with the given name. It returns the value and the embedded depth
-// where it was found.
-//
-func getField(val reflect.Value, fieldname string) (reflect.Value, int) {
-	// do we have a struct in the first place?
-	sval, ok := val.(*reflect.StructValue);
-	if !ok {
-		return nil, 0;
-	}
-	styp := sval.Type().(*reflect.StructType);
-
-	// look for field at the top level
-	if field, ok := styp.FieldByName(fieldname); ok {
-		return sval.Field(field.Index), 0;
-	}
-
-	// look for field in anonymous fields
-	var field reflect.Value;
-	level := 1000;  // infinity (no struct has that many levels)
-	for i := 0; i < styp.NumField(); i++ {
-		f := styp.Field(i);
-		if f.Anonymous {
-			f, l := getField(sval.Field(i), fieldname);
-			// keep the most shallow field
-			if f != nil {
-				switch {
-				case l < level:
-					field, level = f, l;
-				case l == level:
-					// more than one field at the same level,
-					// possibly an error unless there is a more
-					// shallow field found later
-					field = nil;
-				}
-			}
-		}
-	}
-
-	return field, level + 1;
-}
-
-
 // TODO At the moment, unnamed types are simply mapped to the default
 //      names below. For instance, all unnamed arrays are mapped to
 //      'array' which is not really sufficient. Eventually one may want
@@ -613,10 +570,13 @@ func (s *State) eval(fexpr expr, value reflect.Value, index int) bool {
 
 		default:
 			// value is value of named field
-			field, _ := getField(value, t.fieldName);
-			if field == nil {
-				// TODO consider just returning false in this case
-				s.error(fmt.Sprintf("error: no field `%s` in `%s`", t.fieldName, value.Type()));
+			var field reflect.Value;
+			if sval, ok := value.(*reflect.StructValue); ok {
+				field = sval.FieldByName(t.fieldName);
+				if field == nil {
+					// TODO consider just returning false in this case
+					s.error(fmt.Sprintf("error: no field `%s` in `%s`", t.fieldName, value.Type()));
+				}
 			}
 			value = field;
 		}

src/pkg/json/struct.go

@@ -185,7 +185,7 @@ func (b *_StructBuilder) Key(k string) Builder {
 	if v, ok := reflect.Indirect(b.val).(*reflect.StructValue); ok {
 		t := v.Type().(*reflect.StructType);
 		if field, ok := t.FieldByName(k); ok {
-			return &_StructBuilder{ v.Field(field.Index) }
+			return &_StructBuilder{ v.FieldByIndex(field.Index) }
 		}
 		// Again, case-insensitive.
 		for i := 0; i < t.NumField(); i++ {

src/pkg/reflect/all_test.go

@@ -818,3 +818,147 @@ func TestInterfaceSet(t *testing.T) {
 		t.Errorf("Interface Method returned %d; want 250", i);
 	}
 }
+
+type T1 struct { a string; int; }
+
+func TestAnonymousFields(t *testing.T) {
+	var field StructField;
+	var ok bool;
+	var t1 T1;
+	type1 := Typeof(t1).(*StructType);
+	if field, ok = type1.FieldByName("int"); !ok {
+		t.Error("no field 'int'");
+	}
+	if field.Index[0] != 1 {
+		t.Error("field index should be 1; is", field.Index);
+	}
+}
+
+type FTest struct {
+	s interface{};
+	name string;
+	index []int;
+	value int;
+}
+
+type S0 struct {
+	a, b, c, d, d int;
+}
+
+type S1 struct {
+	b int;
+	S0;
+}
+
+type S2 struct {
+	a int;
+	*S1;
+}
+
+type S3 struct {
+	S1;
+	S2;
+	d, e int;
+	*S1;
+}
+
+type S4 struct {
+	*S4;
+	a int;
+}
+
+var fieldTests = []FTest {
+	FTest{ struct{ }{}, "", nil, 0 },
+	FTest{ struct{ }{}, "foo", nil, 0 },
+	FTest{ S0{a: 'a'}, "a", []int{0}, 'a' },
+	FTest{ S0{}, "d", nil, 0 },
+	FTest{ S1{S0: S0{a: 'a'}}, "a", []int{1, 0}, 'a' },
+	FTest{ S1{b: 'b'}, "b", []int{0}, 'b' },
+	FTest{ S1{}, "S0", []int{1}, 0 },
+	FTest{ S1{S0: S0{c: 'c'}}, "c", []int{1, 2}, 'c' },
+	FTest{ S2{a: 'a'}, "a", []int{0}, 'a' },
+	FTest{ S2{}, "S1", []int{1}, 0 },
+	FTest{ S2{S1: &S1{b: 'b'}}, "b", []int{1, 0}, 'b' },
+	FTest{ S2{S1: &S1{S0: S0{c: 'c'}}}, "c", []int{1, 1, 2}, 'c' },
+	FTest{ S2{}, "d", nil, 0 },
+	FTest{ S3{}, "S1", nil, 0 },
+	FTest{ S3{S2: S2{a: 'a'}}, "a", []int{1, 0}, 'a' },
+	FTest{ S3{}, "b", nil, 0 },
+	FTest{ S3{d: 'd'}, "d", []int{2}, 0 },
+	FTest{ S3{e: 'e'}, "e", []int{3}, 'e' },
+	FTest{ S4{a: 'a'}, "a", []int{1}, 'a' },
+	FTest{ S4{}, "b", nil, 0 },
+}
+
+func TestFieldByIndex(t *testing.T) {
+	for _, test := range fieldTests {
+		s := Typeof(test.s).(*StructType);
+		f := s.FieldByIndex(test.index);
+		if f.Name != "" {
+			if test.index != nil {
+				if f.Name != test.name {
+					t.Errorf("%s.%s found; want %s", s.Name(), f.Name, test.name);
+				}
+			} else {
+				t.Errorf("%s.%s found", s.Name(), f.Name);
+			}
+		} else if len(test.index) > 0 {
+			t.Errorf("%s.%s not found", s.Name(), test.name);
+		}
+
+		if test.value != 0 {
+			v := reflect.NewValue(test.s).(*reflect.StructValue).FieldByIndex(test.index);
+			if v != nil {
+				if x, ok := v.Interface().(int); ok {
+					if x != test.value {
+						t.Errorf("%s%v is %d; want %d", s.Name(), test.index, x, test.value);
+					}
+				} else {
+					t.Errorf("%s%v value not an int", s.Name(), test.index);
+				}
+			} else {
+				t.Errorf("%s%v value not found", s.Name(), test.index);
+			}
+		}
+	}
+}
+
+func TestFieldByName(t *testing.T) {
+	for _, test := range fieldTests {
+		s := Typeof(test.s).(*StructType);
+		f, found := s.FieldByName(test.name);
+		if found {
+			if test.index != nil {
+				// Verify field depth and index.
+				if len(f.Index) != len(test.index) {
+					t.Errorf("%s.%s depth %d; want %d", s.Name(), test.name, len(f.Index), len(test.index));
+				} else {
+					for i, x := range f.Index {
+						if x != test.index[i] {
+							t.Errorf("%s.%s.Index[%d] is %d; want %d", s.Name(), test.name, i, x, test.index[i]);
+						}
+					}
+				}
+			} else {
+				t.Errorf("%s.%s found", s.Name(), f.Name);
+			}
+		} else if len(test.index) > 0 {
+			t.Errorf("%s.%s not found", s.Name(), test.name);
+		}
+		
+		if test.value != 0 {
+			v := reflect.NewValue(test.s).(*reflect.StructValue).FieldByName(test.name);
+			if v != nil {
+				if x, ok := v.Interface().(int); ok {
+					if x != test.value {
+						t.Errorf("%s.%s is %d; want %d", s.Name(), test.name, x, test.value);
+					}
+				} else {
+					t.Errorf("%s.%s value not an int", s.Name(), test.name);
+				}
+			} else {
+				t.Errorf("%s.%s value not found", s.Name(), test.name);
+			}
+		}
+	}
+}

src/pkg/reflect/type.go

@@ -463,7 +463,7 @@ type StructField struct {
 	Type Type;
 	Tag string;
 	Offset uintptr;
-	Index int;
+	Index []int;
 	Anonymous bool;
 }
 
@@ -491,24 +491,107 @@ func (t *StructType) Field(i int) (f StructField) {
 		f.Tag = *p.tag;
 	}
 	f.Offset = p.offset;
-	f.Index = i;
+	f.Index = []int{i};
 	return;
 }
 
-// FieldByName returns the field with the provided name and a boolean to indicate
-// that the field was found.
-func (t *StructType) FieldByName(name string) (f StructField, present bool) {
-	for i, p := range t.fields {
-		ff := t.Field(i);
-		if ff.Name == name {
-			f = ff;
-			present = true;
-			break;
+// TODO(gri): Should there be an error/bool indicator if the index
+//            is wrong for FieldByIndex?
+
+// FieldByIndex returns the nested field corresponding to index.
+func (t *StructType) FieldByIndex(index []int) (f StructField) {
+	for i, x := range index {
+		if i > 0 {
+			ft := f.Type;
+			if pt, ok := ft.(*PtrType); ok {
+				ft = pt.Elem();
+			}
+			if st, ok := ft.(*StructType); ok {
+				t = st;
+			} else {
+				var f0 StructField;
+				f = f0;
+				return;
+			}
+		}
+		f = t.Field(x);
+	}
+	return;
+}
+
+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) {
+	fd = inf;	// field depth
+
+	if _, marked := mark[t]; marked {
+		// Struct already seen.
+		return;
+	}
+	mark[t] = true;
+
+	var fi int;	// field index
+L:	for i, _ := range t.fields {
+		f := t.Field(i);
+		d := inf;
+		switch {
+		case f.Name == name:
+			// Matching top-level field.
+			d = depth;
+		case f.Anonymous:
+			ft := f.Type;
+			if pt, ok := ft.(*PtrType); ok {
+				ft = pt.Elem();
+			}
+			switch {
+			case ft.Name() == name:
+				// Matching anonymous top-level field.
+				d = depth;
+			case fd > 0:
+				// No top-level field yet; look inside nested structs.
+				if st, ok := ft.(*StructType); ok {
+					f, d = st.fieldByName(name, mark, depth+1);
+				}
+			}
 		}
+
+		switch {
+		case d < fd:
+			// Found field at shallower depth.
+			ff, fi, fd = f, i, d;
+		case d == fd:
+			// More than one matching field at the same depth (or d, fd == inf).
+			// Same as no field found.
+			fd = inf;
+			if d == depth {
+				// Impossible to find a field at lower depth.
+				break L;
+			}
+		}
+	}
+
+	if fd < inf {
+		// Found matching field.
+		if len(ff.Index) <= depth {
+			ff.Index = make([]int, depth+1);
+		}
+		ff.Index[depth] = fi;
 	}
+
+	mark[t] = false, false;
 	return;
 }
 
+// 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 {
+		ff.Index = ff.Index[0 : fd+1];
+		f, present = ff, true;
+	}
+	return
+}
+
 // NumField returns the number of struct fields.
 func (t *StructType) NumField() int {
 	return len(t.fields);

src/pkg/reflect/value.go

@@ -1126,6 +1126,35 @@ func (v *StructValue) Field(i int) Value {
 	return newValue(f.Type, addr(uintptr(v.addr)+f.Offset), v.canSet && f.PkgPath == "");
 }
 
+// FieldByIndex returns the nested field corresponding to index.
+func (t *StructValue) FieldByIndex(index []int) (v Value) {
+	v = t;
+	for i, x := range index {
+		if i > 0 {
+			if p, ok := v.(*PtrValue); ok {
+				v = p.Elem();
+			}
+			if s, ok := v.(*StructValue); ok {
+				t = s;
+			} else {
+				v = nil;
+				return;
+			}
+		}
+		v = t.Field(x);
+	}
+	return;
+}
+
+// FieldByName returns the struct field with the given name.
+// The result is nil if no field was found.
+func (t *StructValue) FieldByName(name string) Value {
+	if f, ok := t.Type().(*StructType).FieldByName(name); 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/template/template.go

@@ -585,7 +585,7 @@ func (st *state) findVar(s string) reflect.Value {
 		if !ok {
 			return nil
 		}
-		data = data.(*reflect.StructValue).Field(field.Index);
+		data = data.(*reflect.StructValue).FieldByIndex(field.Index);
 	}
 	return data
 }