Return error when object limit exceeded for cached list calls

Since the cache does not implement strongly consistent paginated list
calls, if the Limit option is set and the number of items listed exceeds
this limit, there is no way for the caller to get a complete list of
objects, so return an error here to notify the caller.

Author: chhsia0

pkg/cache/internal/cache_reader.go

@@ -139,15 +139,17 @@ func (c *CacheReader) List(_ context.Context, out client.ObjectList, opts ...cli
 		labelSel = listOpts.LabelSelector
 	}
 
+	// Since the cache does not implement strongly consistent paginated list
+	// calls, if the Limit option is set and the number of items listed exceeds
+	// this limit, there is no way for the caller to get a complete list of
+	// objects, so return an error here to notify the caller.
 	limitSet := listOpts.Limit > 0
+	if limitSet && int64(len(objs)) > listOpts.Limit {
+		return fmt.Errorf("object limit exceeded but paginated list is not supported by the cache")
+	}
 
 	runtimeObjs := make([]runtime.Object, 0, len(objs))
 	for _, item := range objs {
-		// if the Limit option is set and the number of items
-		// listed exceeds this limit, then stop reading.
-		if limitSet && int64(len(runtimeObjs)) >= listOpts.Limit {
-			break
-		}
 		obj, isObj := item.(runtime.Object)
 		if !isObj {
 			return fmt.Errorf("cache contained %T, which is not an Object", item)