fix: return mail and userPrincipalName for GroupMembership user members

Expanded group members are deserialized into typed SDK objects, so user
properties (mail, userPrincipalName) and service principal appId live on
the typed getters rather than in additionalData. Read from the typed
getters with an additionalData fallback, and request the fields explicitly
via a nested $select. Adds direct processMember tests covering typed users,
service principals, and the DirectoryObject fallback path.

Fixes #115

Author: ytsarev

fn.go

@@ -576,7 +576,10 @@ func (g *GraphQuery) fetchGroupMembers(ctx context.Context, client *msgraphsdk.G
 	// See: https://developer.microsoft.com/en-us/graph/known-issues/?search=25984
 	requestConfig := &groups.GroupItemRequestBuilderGetRequestConfiguration{
 		QueryParameters: &groups.GroupItemRequestBuilderGetQueryParameters{
-			Expand: []string{"members"},
+			// Explicitly select the standard member fields via a nested $select so
+			// that user properties such as mail and userPrincipalName are returned
+			// for the expanded members (see issue #115).
+			Expand: []string{"members($select=id,displayName,mail,userPrincipalName,appId)"},
 		},
 	}
 
@@ -639,24 +642,47 @@ func (g *GraphQuery) extractStringProperty(additionalData map[string]interface{}
 	return "", false
 }
 
-// extractUserProperties extracts user-specific properties from additionalData
-func (g *GraphQuery) extractUserProperties(additionalData map[string]interface{}, memberMap map[string]interface{}) {
-	// Extract mail property
-	if mail, ok := g.extractStringProperty(additionalData, "mail"); ok {
-		memberMap["mail"] = mail
+// extractUserProperties extracts user-specific properties.
+// Members expanded via $expand are deserialized into typed objects, so the
+// values live on the typed getters rather than in additionalData. We prefer
+// the typed getters and fall back to additionalData for plain DirectoryObjects.
+func (g *GraphQuery) extractUserProperties(member models.DirectoryObjectable, additionalData map[string]interface{}, memberMap map[string]interface{}) {
+	if user, ok := member.(models.Userable); ok {
+		if mail := ptr.Deref(user.GetMail(), ""); mail != "" {
+			memberMap["mail"] = mail
+		}
+		if upn := ptr.Deref(user.GetUserPrincipalName(), ""); upn != "" {
+			memberMap["userPrincipalName"] = upn
+		}
 	}
 
-	// Extract userPrincipalName property
-	if upn, ok := g.extractStringProperty(additionalData, "userPrincipalName"); ok {
-		memberMap["userPrincipalName"] = upn
+	// Fall back to additionalData when the typed getters did not provide a value.
+	if _, ok := memberMap["mail"]; !ok {
+		if mail, found := g.extractStringProperty(additionalData, "mail"); found {
+			memberMap["mail"] = mail
+		}
+	}
+	if _, ok := memberMap["userPrincipalName"]; !ok {
+		if upn, found := g.extractStringProperty(additionalData, "userPrincipalName"); found {
+			memberMap["userPrincipalName"] = upn
+		}
 	}
 }
 
-// extractServicePrincipalProperties extracts service principal specific properties
-func (g *GraphQuery) extractServicePrincipalProperties(additionalData map[string]interface{}, memberMap map[string]interface{}) {
-	// Extract appId property
-	if appID, ok := g.extractStringProperty(additionalData, "appId"); ok {
-		memberMap["appId"] = appID
+// extractServicePrincipalProperties extracts service principal specific properties.
+// As with users, prefer the typed getter and fall back to additionalData.
+func (g *GraphQuery) extractServicePrincipalProperties(member models.DirectoryObjectable, additionalData map[string]interface{}, memberMap map[string]interface{}) {
+	if sp, ok := member.(models.ServicePrincipalable); ok {
+		if appID := ptr.Deref(sp.GetAppId(), ""); appID != "" {
+			memberMap["appId"] = appID
+		}
+	}
+
+	// Fall back to additionalData when the typed getter did not provide a value.
+	if _, ok := memberMap["appId"]; !ok {
+		if appID, found := g.extractStringProperty(additionalData, "appId"); found {
+			memberMap["appId"] = appID
+		}
 	}
 }
 
@@ -710,9 +736,9 @@ func (g *GraphQuery) processMember(member models.DirectoryObjectable) map[string
 	// Extract type-specific properties
 	switch memberType {
 	case userType:
-		g.extractUserProperties(additionalData, memberMap)
+		g.extractUserProperties(member, additionalData, memberMap)
 	case servicePrincipalType:
-		g.extractServicePrincipalProperties(additionalData, memberMap)
+		g.extractServicePrincipalProperties(member, additionalData, memberMap)
 	}
 
 	return memberMap

fn_test.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/google/go-cmp/cmp"
 	"github.com/google/go-cmp/cmp/cmpopts"
+	"github.com/microsoftgraph/msgraph-sdk-go/models"
 	"github.com/upbound/function-msgraph/input/v1beta1"
 	"google.golang.org/protobuf/testing/protocmp"
 	"google.golang.org/protobuf/types/known/durationpb"
@@ -3815,3 +3816,91 @@ func TestIdentityType(t *testing.T) {
 		})
 	}
 }
+
+// newTestUser builds a typed user directory object, mirroring how the Graph SDK
+// deserializes expanded group members (the values land on the typed struct, not
+// in additionalData).
+func newTestUser() models.DirectoryObjectable {
+	user := models.NewUser()
+	user.SetId(ptr.To("user-id-1"))
+	user.SetDisplayName(ptr.To("Test User 1"))
+	user.SetMail(ptr.To("user1@example.com"))
+	user.SetUserPrincipalName(ptr.To("user1@example.com"))
+	return user
+}
+
+// newTestServicePrincipal builds a typed service principal directory object.
+func newTestServicePrincipal() models.DirectoryObjectable {
+	sp := models.NewServicePrincipal()
+	sp.SetId(ptr.To("sp-id-1"))
+	sp.SetDisplayName(ptr.To("Test Service Principal"))
+	sp.SetAppId(ptr.To("sp-app-id-1"))
+	return sp
+}
+
+// newTestDirectoryObject builds a plain directory object whose properties are
+// only available via additionalData, exercising the fallback extraction path.
+func newTestDirectoryObject() models.DirectoryObjectable {
+	do := models.NewDirectoryObject()
+	do.SetId(ptr.To("user-id-2"))
+	do.SetAdditionalData(map[string]interface{}{
+		"displayName":       "Fallback User",
+		"mail":              "user2@example.com",
+		"userPrincipalName": "user2@example.com",
+	})
+	return do
+}
+
+// TestProcessMember exercises the real member-extraction path (bypassed by the
+// mocked graphQuery in the RunFunction tests). It is the regression test for
+// issue #115: typed user members must expose mail and userPrincipalName.
+func TestProcessMember(t *testing.T) {
+	cases := map[string]struct {
+		reason string
+		member models.DirectoryObjectable
+		want   map[string]interface{}
+	}{
+		"TypedUserIncludesMailAndUPN": {
+			reason: "A typed user member should expose mail and userPrincipalName from the typed getters",
+			member: newTestUser(),
+			want: map[string]interface{}{
+				"id":                "user-id-1",
+				"displayName":       "Test User 1",
+				"type":              "user",
+				"mail":              "user1@example.com",
+				"userPrincipalName": "user1@example.com",
+			},
+		},
+		"TypedServicePrincipalIncludesAppID": {
+			reason: "A typed service principal member should expose appId from the typed getter",
+			member: newTestServicePrincipal(),
+			want: map[string]interface{}{
+				"id":          "sp-id-1",
+				"displayName": "Test Service Principal",
+				"type":        "servicePrincipal",
+				"appId":       "sp-app-id-1",
+			},
+		},
+		"PlainDirectoryObjectUsesAdditionalDataFallback": {
+			reason: "A plain directory object should fall back to additionalData for user properties",
+			member: newTestDirectoryObject(),
+			want: map[string]interface{}{
+				"id":                "user-id-2",
+				"displayName":       "Fallback User",
+				"type":              "user",
+				"mail":              "user2@example.com",
+				"userPrincipalName": "user2@example.com",
+			},
+		},
+	}
+
+	for name, tc := range cases {
+		t.Run(name, func(t *testing.T) {
+			g := &GraphQuery{log: logging.NewNopLogger()}
+			got := g.processMember(tc.member)
+			if diff := cmp.Diff(tc.want, got); diff != "" {
+				t.Errorf("%s\nprocessMember(...): -want, +got:\n%s", tc.reason, diff)
+			}
+		})
+	}
+}