protect against NaN values for sample rate

Author: lobsterkatie

packages/tracing/src/hubextensions.ts

@@ -167,7 +167,9 @@ function getDefaultSampleContext<T extends Transaction>(transaction: T): SampleC
  * Checks the given sample rate to make sure it is valid type and value (a boolean, or a number between 0 and 1).
  */
 function isValidSampleRate(rate: unknown): boolean {
-  if (!(typeof rate === 'number' || typeof rate === 'boolean')) {
+  // we need to check NaN explicitly because it's of type 'number' and therefore wouldn't get caught by this typecheck
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  if (isNaN(rate as any) || !(typeof rate === 'number' || typeof rate === 'boolean')) {
     logger.warn(
       `[Tracing] Given sample rate is invalid. Sample rate must be a boolean or a number between 0 and 1. Got ${JSON.stringify(
         rate,

packages/tracing/test/hub.test.ts

@@ -192,6 +192,13 @@ describe('Hub', () => {
         expect(logger.warn).toHaveBeenCalledWith(expect.stringContaining('Sample rate must be a boolean or a number'));
       });
 
+      it('should reject tracesSampleRates which are NaN', () => {
+        const hub = new Hub(new BrowserClient({ tracesSampleRate: 'dogs!' as any }));
+        hub.startTransaction({ name: 'dogpark' });
+
+        expect(logger.warn).toHaveBeenCalledWith(expect.stringContaining('Sample rate must be a boolean or a number'));
+      });
+
       // the rate might be a boolean, but for our purposes, false is equivalent to 0 and true is equivalent to 1
       it('should reject tracesSampleRates less than 0', () => {
         const hub = new Hub(new BrowserClient({ tracesSampleRate: -26 }));
@@ -216,6 +223,14 @@ describe('Hub', () => {
         expect(logger.warn).toHaveBeenCalledWith(expect.stringContaining('Sample rate must be a boolean or a number'));
       });
 
+      it('should reject tracesSampler return values which are NaN', () => {
+        const tracesSampler = jest.fn().mockReturnValue(NaN);
+        const hub = new Hub(new BrowserClient({ tracesSampler }));
+        hub.startTransaction({ name: 'dogpark' });
+
+        expect(logger.warn).toHaveBeenCalledWith(expect.stringContaining('Sample rate must be a boolean or a number'));
+      });
+
       // the rate might be a boolean, but for our purposes, false is equivalent to 0 and true is equivalent to 1
       it('should reject tracesSampler return values less than 0', () => {
         const tracesSampler = jest.fn().mockReturnValue(-12);
@@ -260,11 +275,11 @@ describe('Hub', () => {
       });
 
       it('should propagate sampling decision to child transactions in XHR header', () => {
-        // TODO this doesn't currently happen, but it should
+        // TODO fix this and write the test
       });
 
       it('should propagate sampling decision to child transactions in fetch header', () => {
-        // TODO this doesn't currently happen, but it should
+        // TODO fix this and write the test
       });
 
       it("should inherit parent's sampling decision when creating a new transaction if tracesSampler is undefined", () => {