From ea1733095536ecee793c8029d46844632d7a5084 Mon Sep 17 00:00:00 2001
From: Laurent Christophe <lachrist@vub.ac.be>
Date: Tue, 15 Feb 2022 17:08:39 +0100
Subject: [PATCH] fix: verify that toString method returned a string

Failure happened when the toString method of a recorded value returned a non-string value (specifically null or undefined). In this case, we now fallback to safe stringify operation.
---
 components/serialization/default/index.mjs      |  4 ++++
 components/serialization/default/index.test.mjs | 16 ++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/components/serialization/default/index.mjs b/components/serialization/default/index.mjs
index 232907269..05dd7574f 100644
--- a/components/serialization/default/index.mjs
+++ b/components/serialization/default/index.mjs
@@ -124,6 +124,10 @@ export default (dependencies) => {
               logDebug("%o.toString() failure >> %O", value, error);
               serial.print = apply(toString, value, noargs);
             }
+            if (typeof serial.print !== "string") {
+              logDebug("%o.toString() returned a non-string result");
+              serial.print = apply(toString, value, noargs);
+            }
           } else {
             serial.print = apply(toString, value, noargs);
           }
diff --git a/components/serialization/default/index.test.mjs b/components/serialization/default/index.test.mjs
index 408e7b3b2..47d8b68d0 100644
--- a/components/serialization/default/index.test.mjs
+++ b/components/serialization/default/index.test.mjs
@@ -150,6 +150,22 @@ assertDeepEqual(
     print: "[object Object]",
   },
 );
+assertDeepEqual(
+  testSerialize(
+    {
+      method: "toString",
+      "include-constructor-name": false,
+    },
+    {
+      toString: () => 123,
+    },
+  ),
+  {
+    type: "object",
+    index: 1,
+    print: "[object Object]",
+  },
+);
 // function (toString)
 assertDeepEqual(
   testSerialize(