From 9bb35692413b59dce3438926a2b5b377c3e44573 Mon Sep 17 00:00:00 2001
From: Ulad Kasach <uladkasach@gmail.com>
Date: Fri, 25 Nov 2022 17:31:47 -0500
Subject: [PATCH] feat(resiliance): automatically recover from malformed cache
 files; just warn and move on

---
 src/cache.ts | 28 +++++++++++++++++++++++-----
 1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/src/cache.ts b/src/cache.ts
index ef7c988..d75f90a 100644
--- a/src/cache.ts
+++ b/src/cache.ts
@@ -217,11 +217,29 @@ export const createCache = ({
       key,
     });
     if (cacheContentSerialized === undefined) return undefined; // if not in cache, then undefined
-    const cacheContent = JSON.parse(cacheContentSerialized);
-    if (isRecordExpired(cacheContent)) return undefined; // if already expired, then undefined
-    if (cacheContent.deserializedForObservability)
-      return JSON.stringify(cacheContent.value); // if it had been deserialized for observability, reserialize it
-    return cacheContent.value as string; // otherwise, its in the cache and not expired, so return the value
+    try {
+      const cacheContent = JSON.parse(cacheContentSerialized);
+      if (isRecordExpired(cacheContent)) return undefined; // if already expired, then undefined
+      if (cacheContent.deserializedForObservability)
+        return JSON.stringify(cacheContent.value); // if it had been deserialized for observability, reserialize it
+      return cacheContent.value as string; // otherwise, its in the cache and not expired, so return the value
+    } catch (error) {
+      // if it was a json parsing error, warn about it and treat the key as invalid
+      if (
+        error instanceof Error &&
+        error.message.includes('Unexpected string in JSON at position')
+      ) {
+        // eslint-disable-next-line no-console
+        console.warn(
+          'simple-on-disk-cache: detected unparseable cache file. treating the result as invalid. this should not have occured',
+          { key },
+        );
+        return undefined;
+      }
+
+      // otherwise, propagate the error, we dont know how to handle it
+      throw error;
+    }
   };
 
   /**