chore(flags): Add new debugging property $used_bootstrap_value, $feature_flag_bootstrapped_response and $feature_flag_bootstrapped_payload to $feature_flag_called event

cypress/e2e/capture.cy.ts

@@ -160,6 +160,31 @@ describe('Event capture', () => {
         cy.phCaptures().should('include', '$feature_flag_called')
     })
 
+    it('captures $feature_flag_called with bootstrapped value properties', () => {
+        start({
+            options: {
+                bootstrap: {
+                    featureFlags: {
+                        'some-feature': 'some-value',
+                    },
+                    featureFlagPayloads: {
+                        'some-feature': 'some-payload',
+                    },
+                },
+            },
+        })
+
+        cy.get('[data-cy-feature-flag-button]').click()
+
+        cy.phCaptures({ full: true }).then((captures) => {
+            const flagCallEvents = captures.filter((capture) => capture.event === '$feature_flag_called')
+            expect(flagCallEvents.length).to.eq(1)
+            const flagCallEvent = flagCallEvents[0]
+            expect(flagCallEvent.properties.$feature_flag_bootstrapped_response).to.equal('some-value')
+            expect(flagCallEvent.properties.$feature_flag_bootstrapped_payload).to.equal('some-payload')
+        })
+    })
+
     it('captures rage clicks', () => {
         start({ options: { rageclick: true } })
 

src/posthog-featureflags.ts

@@ -244,7 +244,14 @@ export class PostHogFeatureFlags {
                 }
                 this.instance.persistence?.register({ [FLAG_CALL_REPORTED]: flagCallReported })
 
-                this.instance.capture('$feature_flag_called', { $feature_flag: key, $feature_flag_response: flagValue })
+                this.instance.capture('$feature_flag_called', {
+                    $feature_flag: key,
+                    $feature_flag_response: flagValue,
+                    $feature_flag_payload: this.getFeatureFlagPayload(key) || null,
+                    $feature_flag_bootstrapped_response: this.instance.config.bootstrap?.featureFlags?.[key] || null,
+                    $feature_flag_bootstrapped_payload:
+                        this.instance.config.bootstrap?.featureFlagPayloads?.[key] || null,
+                })
             }
         }
         return flagValue