ref(core): Optimize Scope.setTag bundle size and adjust test (#18182)

Two changes:
1. Reduce bundle size slightly by optimizing `setTag` (+ adding some
more tests around setTag(s))
2. Adjust the integration test message since we no longer classify the 
SUT behaviour as a bug

Author: Lms24

dev-packages/browser-integration-tests/suites/public-api/setTag/with_non_primitives/test.ts

@@ -3,16 +3,21 @@ import type { Event } from '@sentry/core';
 import { sentryTest } from '../../../../utils/fixtures';
 import { getFirstSentryEnvelopeRequest } from '../../../../utils/helpers';
 
-sentryTest('[bug] accepts non-primitive tags', async ({ getLocalTestUrl, page }) => {
-  // this is a bug that went unnoticed due to type definitions and a bad assertion
-  // TODO: We should not accept non-primitive tags. Fix this as a follow-up.
+sentryTest('accepts and sends non-primitive tags', async ({ getLocalTestUrl, page }) => {
+  // Technically, accepting and sending non-primitive tags is a specification violation.
+  // This slipped through because a previous version of this test should have ensured that
+  // we don't accept non-primitive tags. However, the test was flawed.
+  // Turns out, Relay and our product handle invalid tag values gracefully.
+  // Our type definitions for setTag(s) also only allow primitive values.
+  // Therefore (to save some bundle size), we'll continue accepting and sending non-primitive
+  // tag values for now (but not adjust types).
+  // This test documents this decision, so that we know why we're accepting non-primitive tags.
   const url = await getLocalTestUrl({ testDir: __dirname });
 
   const eventData = await getFirstSentryEnvelopeRequest<Event>(page, url);
 
   expect(eventData.message).toBe('non_primitives');
 
-  // TODO: This should be an empty object but instead, it is:
   expect(eventData.tags).toEqual({
     tag_1: {},
     tag_2: [],

packages/core/src/scope.ts

@@ -291,9 +291,7 @@ export class Scope {
    * Set a single tag that will be sent as tags data with the event.
    */
   public setTag(key: string, value: Primitive): this {
-    this._tags = { ...this._tags, [key]: value };
-    this._notifyScopeListeners();
-    return this;
+    return this.setTags({ [key]: value });
   }
 
   /**

packages/core/test/lib/scope.test.ts

@@ -140,16 +140,47 @@ describe('Scope', () => {
       expect(scope['_extra']).toEqual({ a: undefined });
     });
 
-    test('setTag', () => {
-      const scope = new Scope();
-      scope.setTag('a', 'b');
-      expect(scope['_tags']).toEqual({ a: 'b' });
+    describe('setTag', () => {
+      it('sets a tag', () => {
+        const scope = new Scope();
+        scope.setTag('a', 'b');
+        expect(scope['_tags']).toEqual({ a: 'b' });
+      });
+
+      it('sets a tag with undefined', () => {
+        const scope = new Scope();
+        scope.setTag('a', 'b');
+        scope.setTag('a', undefined);
+        expect(scope['_tags']).toEqual({ a: undefined });
+      });
+
+      it('notifies scope listeners once per call', () => {
+        const scope = new Scope();
+        const listener = vi.fn();
+
+        scope.addScopeListener(listener);
+        scope.setTag('a', 'b');
+        scope.setTag('a', 'c');
+
+        expect(listener).toHaveBeenCalledTimes(2);
+      });
     });
 
-    test('setTags', () => {
-      const scope = new Scope();
-      scope.setTags({ a: 'b' });
-      expect(scope['_tags']).toEqual({ a: 'b' });
+    describe('setTags', () => {
+      it('sets tags', () => {
+        const scope = new Scope();
+        scope.setTags({ a: 'b', c: 1 });
+        expect(scope['_tags']).toEqual({ a: 'b', c: 1 });
+      });
+
+      it('notifies scope listeners once per call', () => {
+        const scope = new Scope();
+        const listener = vi.fn();
+        scope.addScopeListener(listener);
+        scope.setTags({ a: 'b', c: 'd' });
+        scope.setTags({ a: 'e', f: 'g' });
+        expect(listener).toHaveBeenCalledTimes(2);
+      });
     });
 
     test('setUser', () => {