fix(core): serialize bigint in metadata to string (#619)

* fix(core): serialize bigint in metadata to string

* chore: extracted replacer into SegmentUtils

* Update subsegment.d.ts

Co-authored-by: Carol Abadeer <60774943+carolabadeer@users.noreply.github.com>

* Update segment.d.ts

Co-authored-by: Carol Abadeer <60774943+carolabadeer@users.noreply.github.com>

---------

Co-authored-by: Andrea Amorosi <aamorosi@amazon.es>
Co-authored-by: Carol Abadeer <60774943+carolabadeer@users.noreply.github.com>

packages/core/lib/segments/attributes/subsegment.d.ts

@@ -61,6 +61,8 @@ declare class Subsegment {
   toString(): string;
 
   toJSON(): { [key: string]: any };
+
+  serialize(subsegment?: Subsegment): string;
 }
 
 export = Subsegment;

packages/core/lib/segments/attributes/subsegment.js

@@ -401,15 +401,15 @@ Subsegment.prototype.format = function format() {
     this.trace_id = this.segment.trace_id;
   }
 
-  return JSON.stringify(this);
+  return this.serialize();
 };
 
 /**
  * Returns the formatted subsegment JSON string.
  */
 
 Subsegment.prototype.toString = function toString() {
-  return JSON.stringify(this);
+  return this.serialize();
 };
 
 Subsegment.prototype.toJSON = function toJSON() {
@@ -428,4 +428,14 @@ Subsegment.prototype.toJSON = function toJSON() {
   return thisCopy;
 };
 
+/**
+ * Returns the serialized subsegment JSON string, replacing any BigInts with strings.
+ */
+Subsegment.prototype.serialize = function serialize(object) {
+  return JSON.stringify(
+    object ?? this,
+    SegmentUtils.getJsonStringifyReplacer()
+  );
+};
+
 module.exports = Subsegment;

packages/core/lib/segments/segment.d.ts

@@ -64,6 +64,8 @@ declare class Segment {
   format(): string;
 
   toString(): string;
+
+  serialize(segment?: Segment): string;
 }
 
 export = Segment;

packages/core/lib/segments/segment.js

@@ -431,11 +431,18 @@ Segment.prototype.format = function format() {
     false
   );
 
-  return JSON.stringify(thisCopy);
+  return this.serialize(thisCopy);
 };
 
 Segment.prototype.toString = function toString() {
-  return JSON.stringify(this);
+  return this.serialize();
+};
+
+Segment.prototype.serialize = function serialize(object) {
+  return JSON.stringify(
+    object ?? this,
+    SegmentUtils.getJsonStringifyReplacer()
+  );
 };
 
 module.exports = Segment;

packages/core/lib/segments/segment_utils.d.ts

@@ -17,3 +17,5 @@ export function setStreamingThreshold(threshold: number): void;
 export function getStreamingThreshold(): number;
 
 export function getHttpResponseData(res: http.ServerResponse): object;
+
+export function getJsonStringifyReplacer(): (key: string, value: any) => any;

packages/core/lib/segments/segment_utils.js

@@ -67,6 +67,14 @@ var utils = {
       ret.content_length = safeParseInt(res.headers['content-length']);
     }
     return ret;
+  },
+
+  getJsonStringifyReplacer: () => (_, value) => {
+    if (typeof value === 'bigint') {
+      return value.toString();
+    }
+
+    return value;
   }
 };
 

packages/core/test/unit/segments/attributes/subsegment.test.js

@@ -332,6 +332,12 @@ describe('Subsegment', function() {
       child.flush();
       emitStub.should.have.been.called;
     });
+
+    it('should stringify bigint objects correctly', function() {
+      child.addMetadata('key', BigInt(9007199254740991));
+      child.flush();
+      emitStub.should.have.been.calledOnce;
+    });
   });
 
   describe('#streamSubsegments', function() {

packages/core/test/unit/segments/segment_utils.test.js

@@ -43,4 +43,14 @@ describe('SegmentUtils', function() {
       assert.deepEqual(emptyRes, {});
     });
   });
+
+  describe('#getJsonStringifyReplacer', () => {
+    it('should stringify BigInts', () => {
+      const obj = {foo: 1n, bar: BigInt(2)};
+      const replacer = SegmentUtils.getJsonStringifyReplacer();
+      const result = JSON.stringify(obj, replacer);
+
+      assert.equal(result, '{"foo":"1","bar":"2"}');
+    });
+  });
 });