fix: #186 avoid infinite recursion in filter method

lib/raygun.messageBuilder.ts

@@ -31,18 +31,37 @@ type UserMessageData = RawUserData | string | undefined;
 const humanString = require("object-to-human-string");
 const packageDetails = require("../package.json");
 
-function filterKeys(obj: object, filters: string[]): object {
+/**
+ * Filter properties in obj according to provided filters.
+ * Also removes any recursive self-referencing object.
+ * @param obj object to apply filter
+ * @param filters list of keys to filter
+ * @param explored Set that contains already explored nodes, used internally
+ */
+function filterKeys(
+  obj: object,
+  filters: string[],
+  explored: Set<object> | null = null,
+): object {
   if (!obj || !filters || typeof obj !== "object") {
     return obj;
   }
+
+  // create or update the explored set with the incoming object
+  const _explored = explored?.add(obj) || new Set([obj]);
+
   // Make temporary copy of the object to avoid mutating the original
   // Cast to Record<string, object> to enforce type check and avoid using any
   const _obj = { ...obj } as Record<string, object>;
-  Object.keys(obj).forEach(function (i) {
-    if (filters.indexOf(i) > -1) {
-      delete _obj[i];
+
+  Object.keys(obj).forEach(function (key) {
+    // Remove child if:
+    // - the key is in the filter array
+    // - the value is already in the explored Set
+    if (filters.indexOf(key) > -1 || _explored.has(_obj[key])) {
+      delete _obj[key];
     } else {
-      _obj[i] = filterKeys(_obj[i], filters);
+      _obj[key] = filterKeys(_obj[key], filters, _explored);
     }
   });
   return _obj;

test/raygun.messageBuilder_test.js

@@ -377,6 +377,10 @@ test("filter keys tests", function (t) {
   });
   var message = builder.build();
 
+  // Original object should not be modified
+  t.equal(body.username, "[email protected]");
+  t.equal(body.password, "nice try");
+
   t.test("form is filtered", function (tt) {
     tt.equal(message.details.request.form.username, undefined);
     tt.equal(message.details.request.form.password, undefined);
@@ -399,6 +403,49 @@ test("filter keys tests", function (t) {
   });
 });
 
+test("avoid infinite recursion in filter method", function (t) {
+  let builder = new MessageBuilder({
+    filters: ["filtered"],
+  });
+
+  // body self-references, causing a potential infinite recursion in the filter method
+  // Causes exception: Maximum call stack size exceeded
+  let body = {
+    key: "value",
+    filtered: true,
+  };
+  // second level self-reference
+  let other = {
+    body: body,
+    filtered: true,
+  };
+  body.myself = body;
+  body.other = other;
+
+  let queryString = {};
+  let headers = {};
+
+  // performs filter on set
+  builder.setRequestDetails({
+    body: body,
+    query: queryString,
+    headers: headers,
+  });
+  var message = builder.build();
+
+  // key is preserved
+  t.equal(message.details.request.form.key, "value");
+  // property in "filters" is filtered
+  t.equal(message.details.request.form.filtered, undefined);
+  t.equal(message.details.request.form.other.filtered, undefined);
+  // self-referencing objects are also not included
+  t.equal(message.details.request.form.myself, undefined);
+  t.equal(message.details.request.form.other.body, undefined);
+
+  // test should finish
+  t.end();
+});
+
 test("custom tags", function (t) {
   t.test("with array", function (tt) {
     var builder = new MessageBuilder();