data: always require at least one step for nesting compositions

1 files changed, 4 insertions, 0 deletions

diff --git a/src/data/things/composite.js b/src/data/things/composite.js
index c3b08f8..113f0a4 100644
--- a/src/data/things/composite.js
+++ b/src/data/things/composite.js
@@ -637,6 +637,10 @@ export function compositeFrom(description) {
 
   const compositionNests = description.compose ?? true;
 
+  if (compositionNests && empty(steps)) {
+    aggregate.push(new TypeError(`Expected at least one step`));
+  }
+
   // Steps default to exposing if using a shorthand syntax where flags aren't
   // specified at all.
   const stepsExpose =