fix(engine): add debug logging when lookup returns empty (#32205)

When lookup cannot find the requested resource (apierrors.IsNotFound),
add slog.Debug() calls with structured fields (apiVersion, kind,
namespace, name) so that users running helm template --debug can see
why lookup returned an empty map instead of silently swallowing the
not-found result.

Fixes: https://github.com/helm/helm/issues/32101

Signed-off-by: Ogulcan Aydogan <ogulcanaydogan@hotmail.com>

pkg/engine/lookup_func.go

@@ -73,6 +73,12 @@ func newLookupFunction(clientProvider ClientProvider) lookupFunc {
 				if apierrors.IsNotFound(err) {
 					// Just return an empty interface when the object was not found.
 					// That way, users can use `if not (lookup ...)` in their templates.
+					slog.Debug("lookup: resource not found",
+						slog.String("apiVersion", apiversion),
+						slog.String("kind", kind),
+						slog.String("namespace", namespace),
+						slog.String("name", name),
+					)
 					return map[string]any{}, nil
 				}
 				return map[string]any{}, err
@@ -85,6 +91,11 @@ func newLookupFunction(clientProvider ClientProvider) lookupFunc {
 			if apierrors.IsNotFound(err) {
 				// Just return an empty interface when the object was not found.
 				// That way, users can use `if not (lookup ...)` in their templates.
+				slog.Debug("lookup: resource list not found",
+					slog.String("apiVersion", apiversion),
+					slog.String("kind", kind),
+					slog.String("namespace", namespace),
+				)
 				return map[string]any{}, nil
 			}
 			return map[string]any{}, err