Review comments #2.

attributes/attributes.go

@@ -51,7 +51,7 @@ func New(kvs ...interface{}) *Attributes {
 // remove an existing key, use a nil value.
 func (a *Attributes) WithValues(kvs ...interface{}) *Attributes {
 	if a == nil {
-		a = New()
+		return New(kvs...)
 	}
 	if len(kvs)%2 != 0 {
 		panic(fmt.Sprintf("attributes.New called with unexpected input: len(kvs) = %v", len(kvs)))
@@ -69,5 +69,8 @@ func (a *Attributes) WithValues(kvs ...interface{}) *Attributes {
 // Value returns the value associated with these attributes for key, or nil if
 // no value is associated with key.
 func (a *Attributes) Value(key interface{}) interface{} {
+	if a == nil {
+		return nil
+	}
 	return a.m[key]
 }

balancer/weightedroundrobin/weightedroundrobin.go

@@ -37,22 +37,24 @@ type AddrInfo struct {
 }
 
 // SetAddrInfo sets addInfo in the Attributes field of addr.
-func SetAddrInfo(addrInfo *AddrInfo, addr *resolver.Address) {
+// This is an EXPERIMENTAL API.
+func SetAddrInfo(addrInfo AddrInfo, addr *resolver.Address) {
 	addr.Attributes = addr.Attributes.WithValues(attributeKey{}, addrInfo)
 }
 
 // GetAddrInfo returns the AddrInfo stored in the Attributes fields of addr.
 // Returns nil if no AddrInfo is present.
-func GetAddrInfo(addr *resolver.Address) *AddrInfo {
+// This is an EXPERIMENTAL API.
+func GetAddrInfo(addr *resolver.Address) AddrInfo {
 	if addr == nil || addr.Attributes == nil {
-		return nil
+		return AddrInfo{}
 	}
 	ai := addr.Attributes.Value(attributeKey{})
 	if ai == nil {
-		return nil
+		return AddrInfo{}
 	}
-	if _, ok := ai.(*AddrInfo); !ok {
-		return nil
+	if _, ok := ai.(AddrInfo); !ok {
+		return AddrInfo{}
 	}
-	return ai.(*AddrInfo)
+	return ai.(AddrInfo)
 }

balancer/weightedroundrobin/weightedwoundrobin_test.go

@@ -29,33 +29,33 @@ import (
 func TestAddAddrInfoToAndFromAttributes(t *testing.T) {
 	tests := []struct {
 		desc            string
-		inputAddrInfo   *AddrInfo
+		inputAddrInfo   AddrInfo
 		inputAttributes *attributes.Attributes
-		wantAddrInfo    *AddrInfo
+		wantAddrInfo    AddrInfo
 	}{
 		{
 			desc:            "empty attributes",
-			inputAddrInfo:   &AddrInfo{Weight: 100},
+			inputAddrInfo:   AddrInfo{Weight: 100},
 			inputAttributes: nil,
-			wantAddrInfo:    &AddrInfo{Weight: 100},
+			wantAddrInfo:    AddrInfo{Weight: 100},
 		},
 		{
 			desc:            "non-empty attributes",
-			inputAddrInfo:   &AddrInfo{Weight: 100},
+			inputAddrInfo:   AddrInfo{Weight: 100},
 			inputAttributes: attributes.New("foo", "bar"),
-			wantAddrInfo:    &AddrInfo{Weight: 100},
+			wantAddrInfo:    AddrInfo{Weight: 100},
 		},
 		{
 			desc:            "addrInfo not present in empty attributes",
-			inputAddrInfo:   nil,
+			inputAddrInfo:   AddrInfo{},
 			inputAttributes: nil,
-			wantAddrInfo:    nil,
+			wantAddrInfo:    AddrInfo{},
 		},
 		{
 			desc:            "addrInfo not present in non-empty attributes",
-			inputAddrInfo:   nil,
+			inputAddrInfo:   AddrInfo{},
 			inputAttributes: attributes.New("foo", "bar"),
-			wantAddrInfo:    nil,
+			wantAddrInfo:    AddrInfo{},
 		},
 	}