fix: ensure Fetch API tags field is always an array, never null

- Add TagsOrEmpty in pkg/grpc/common.go for proto/cloudevent conversion
- Normalize tags in eventrepo (toCloudEvent, ListCloudEventsFromIndexes)
- Normalize tags in indexToModel for latestIndex/indexes GraphQL responses
- Schema: tags type [String!]! so API contract guarantees non-null array
- Regenerate gqlgen

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: zer0stars

internal/graph/convert.go

@@ -56,6 +56,7 @@ func resolveLimit(limit *int) int {
 // indexToModel converts a CloudEvent index entry to the GraphQL model,
 // using the CloudEventHeader from the library directly.
 func indexToModel(idx cloudevent.CloudEvent[eventrepo.ObjectInfo]) *model.CloudEventIndex {
+	idx.CloudEventHeader.Tags = grpc.TagsOrEmpty(idx.CloudEventHeader.Tags)
 	return &model.CloudEventIndex{
 		Header:   &idx.CloudEventHeader,
 		IndexKey: idx.Data.Key,

internal/graph/generated.go

@@ -190,7 +190,9 @@ func (s *Service) ListCloudEventsFromIndexes(ctx context.Context, indexes []clou
 	for i := range indexes {
 		// Some objects have multiple cloud events so we cache the objects to avoid fetching them multiple times.
 		if data, ok := objectsByKeys[indexes[i].Data.Key]; ok {
-			events[i] = cloudevent.RawEvent{CloudEventHeader: indexes[i].CloudEventHeader, Data: data}
+			hdr := indexes[i].CloudEventHeader
+			hdr.Tags = grpc.TagsOrEmpty(hdr.Tags)
+			events[i] = cloudevent.RawEvent{CloudEventHeader: hdr, Data: data}
 			continue
 		}
 		events[i], err = s.GetCloudEventFromIndex(ctx, indexes[i], bucketName)
@@ -315,6 +317,7 @@ func toCloudEvent(dbHdr *cloudevent.CloudEventHeader, data []byte) (cloudevent.R
 		ev.Data = nil // never expose decoded bytes in Data
 	}
 	ev.CloudEventHeader = *dbHdr
+	ev.CloudEventHeader.Tags = grpc.TagsOrEmpty(ev.CloudEventHeader.Tags)
 	return ev, nil
 }
 

pkg/eventrepo/eventrepo.go

@@ -7,6 +7,15 @@ import (
 	"google.golang.org/protobuf/types/known/timestamppb"
 )
 
+// TagsOrEmpty returns the slice if non-nil and non-empty, otherwise a non-nil empty slice.
+// Ensures API always returns an array for tags, never null.
+func TagsOrEmpty(tags []string) []string {
+	if len(tags) > 0 {
+		return tags
+	}
+	return []string{}
+}
+
 // AsRawCloudEvent converts the CloudEvent to a cloudevent.RawEvent.
 func (c *CloudEvent) AsRawCloudEvent() cloudevent.RawEvent {
 	return cloudevent.RawEvent{
@@ -41,7 +50,7 @@ func (c *CloudEventHeader) AsCloudEventHeader() cloudevent.CloudEventHeader {
 		DataVersion:     c.GetDataVersion(),
 		Extras:          extras,
 		Signature:       c.GetSignature(),
-		Tags:            c.GetTags(),
+		Tags:            TagsOrEmpty(c.GetTags()),
 	}
 }
 
@@ -72,7 +81,7 @@ func CloudEventHeaderToProto(event *cloudevent.CloudEventHeader) *CloudEventHead
 		DataVersion:     event.DataVersion,
 		Extras:          extras,
 		Signature:       event.Signature,
-		Tags:            event.Tags,
+		Tags:            TagsOrEmpty(event.Tags),
 	}
 }
 

pkg/grpc/common.go

@@ -60,7 +60,7 @@ type CloudEventHeader {
   dataschema: String
   dataversion: String
   signature: String
-  tags: [String!]
+  tags: [String!]!
 }
 
 """