util: throw toJSON errors when formatting %j

Previously all errors resulting from JSON.stringify were treated as a
proof for circularity of the object structure. That is not the case if
the `toJSON` method of the object throws an error. Explicitly check for
the exact error message when determining the object structure's
cyclicity.

PR-URL: #11708
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Sakthipriyan Vairamani <[email protected]>
Reviewed-By: Michaël Zasso <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>

Author: TimothyGu

lib/util.js

@@ -38,13 +38,17 @@ const inspectDefaultOptions = Object.seal({
   breakLength: 60
 });
 
+const CIRCULAR_ERROR_MESSAGE = 'Converting circular structure to JSON';
+
 var Debug;
 
 function tryStringify(arg) {
   try {
     return JSON.stringify(arg);
-  } catch (_) {
-    return '[Circular]';
+  } catch (err) {
+    if (err.name === 'TypeError' && err.message === CIRCULAR_ERROR_MESSAGE)
+      return '[Circular]';
+    throw err;
   }
 }
 

test/parallel/test-util-format.js

@@ -86,6 +86,16 @@ assert.strictEqual(util.format('o: %j, a: %j'), 'o: %j, a: %j');
   assert.strictEqual(util.format('%j', o), '[Circular]');
 }
 
+{
+  const o = {
+    toJSON() {
+      throw new Error('Not a circular object but still not serializable');
+    }
+  };
+  assert.throws(() => util.format('%j', o),
+                /^Error: Not a circular object but still not serializable$/);
+}
+
 // Errors
 const err = new Error('foo');
 assert.strictEqual(util.format(err), err.stack);