From 5440b54618affd2aaeed954d2274b90ffd0dfef4 Mon Sep 17 00:00:00 2001
From: Kari Lavikka <kari.lavikka@bdb.fi>
Date: Thu, 2 Dec 2021 13:40:34 +0200
Subject: [PATCH] chore: add descriptive error message to `removeUnreachable`

---
 src/Utils/removeUnreachable.ts | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/Utils/removeUnreachable.ts b/src/Utils/removeUnreachable.ts
index 53ccc61fc..cc805223f 100644
--- a/src/Utils/removeUnreachable.ts
+++ b/src/Utils/removeUnreachable.ts
@@ -18,7 +18,11 @@ function addReachable(
             return;
         }
         reachable.add(typeName);
-        addReachable(definitions[typeName], definitions, reachable);
+        const refDefinition = definitions[typeName];
+        if (!refDefinition) {
+            throw new Error(`Encountered a reference to a missing definition: "${definition.$ref}". This is a bug.`);
+        }
+        addReachable(refDefinition, definitions, reachable);
     } else if (definition.anyOf) {
         for (const def of definition.anyOf) {
             addReachable(def, definitions, reachable);