SNOW-959721 TypeError: Converting circular structure to JSON in isVal…

…idAsync exception handling (#688)

lib/connection/connection.js

@@ -171,7 +171,7 @@ function Connection(context)
     }
     catch (e)
     {
-      Logger.getInstance().trace('Connection heartbeat failed: %s', JSON.stringify(e));
+      Logger.getInstance().trace('Connection heartbeat failed: %s', JSON.stringify(e, Util.getCircularReplacer()));
       return false;
     }
   };

lib/util.js

@@ -603,3 +603,28 @@ exports.convertSmkIdToString = function (body)
 {
   return body.replace(/"smkId" : ([0-9]*)/g, '"smkId" : "$1"');
 };
+
+/**
+ * Under some circumstances the object passed to JSON.stringify in exception handling
+ * can contain circular reference, on which JSON.stringify bails out
+ * MDN way of handling such error
+ * @returns string
+ */
+exports.getCircularReplacer = function() {
+  const ancestors = [];
+  return function (key, value) {
+      if (typeof value !== "object" || value === null) {
+          return value;
+      }
+      // `this` is the object that value is contained in,
+      // i.e., its direct parent.
+      while (ancestors.length > 0 && ancestors[ancestors.length - 1] !== this) {
+          ancestors.pop();
+      }
+      if (ancestors.includes(value)) {
+          return "[Circular]";
+      }
+      ancestors.push(value);
+      return value;
+  };
+};

test/unit/util_test.js

@@ -804,4 +804,22 @@ describe('Util', function ()
       });
     });
   });
+
+  describe("Util Test - handling circular reference in isValidAsync exception handling", () => {
+    let shouldMatchNonCircular = '{"one":1,"two":2}';
+    let shouldMatchCircular = '{"one":1,"two":2,"myself":"[Circular]"}';
+
+    it("non-circular reference is handled correctly by JSON.stringify replacer", () => {
+      const a = {"one": 1, "two": 2};
+      const replacedA = JSON.stringify(a, Util.getCircularReplacer());
+      assert.deepEqual(replacedA, shouldMatchNonCircular);
+    });
+
+    it("circular reference is handled correctly by JSON.stringify replacer", () => {
+      const b = {"one": 1, "two": 2};
+      b.myself = b;
+      const replacedB = JSON.stringify(b, Util.getCircularReplacer());
+      assert.deepEqual(replacedB, shouldMatchCircular);
+    });
+  });
 });