feat(feature-flags): support quota limiting for feature flags (#1758)

* did the damn thing

* clean up tests

Author: dmarticus

src/__tests__/posthog-core.loaded.test.ts

@@ -15,7 +15,7 @@ describe('loaded() with flags', () => {
             ...config,
             loaded: (ph) => {
                 ph.capture = jest.fn()
-                ph._send_request = jest.fn(({ callback }) => callback?.({ status: 200, json: {} }))
+                ph._send_request = jest.fn(({ callback }) => callback?.({ statusCode: 200, json: {} }))
                 ph._start_queue_if_opted_in = jest.fn()
 
                 jest.spyOn(ph.featureFlags, 'setGroupPropertiesForFlags')
@@ -106,4 +106,57 @@ describe('loaded() with flags', () => {
             expect(instance._send_request).toHaveBeenCalledTimes(1)
         })
     })
+
+    describe('quota limiting', () => {
+        beforeEach(async () => {
+            instance = await createPosthog()
+        })
+
+        it.each([
+            {
+                name: 'does not process feature flags when quota limited',
+                response: {
+                    quotaLimited: ['feature_flags'],
+                    featureFlags: { 'test-flag': true },
+                },
+                expectedCall: false,
+                expectedArgs: undefined,
+            },
+            {
+                name: 'processes feature flags when not quota limited',
+                response: {
+                    featureFlags: { 'test-flag': true },
+                },
+                expectedCall: true,
+                expectedArgs: { featureFlags: { 'test-flag': true } },
+            },
+            {
+                name: 'processes feature flags when other resources are quota limited',
+                response: {
+                    quotaLimited: ['recordings'],
+                    featureFlags: { 'test-flag': true },
+                },
+                expectedCall: true,
+                expectedArgs: { quotaLimited: ['recordings'], featureFlags: { 'test-flag': true } },
+            },
+        ])('$name', async ({ response, expectedCall, expectedArgs }) => {
+            instance._send_request = jest.fn(({ callback }) =>
+                callback?.({
+                    statusCode: 200,
+                    json: response,
+                })
+            )
+
+            const receivedFeatureFlagsSpy = jest.spyOn(instance.featureFlags, 'receivedFeatureFlags')
+
+            instance.featureFlags._callDecideEndpoint()
+            jest.runAllTimers()
+
+            if (expectedCall) {
+                expect(receivedFeatureFlagsSpy).toHaveBeenCalledWith(expectedArgs, false)
+            } else {
+                expect(receivedFeatureFlagsSpy).not.toHaveBeenCalled()
+            }
+        })
+    })
 })

src/posthog-featureflags.ts

@@ -104,6 +104,11 @@ type OverrideFeatureFlagsOptions =
     | FeatureFlagOverrides // set variants directly
     | FeatureFlagOverrideOptions
 
+export enum QuotaLimitedResource {
+    FeatureFlags = 'feature_flags',
+    Recordings = 'recordings',
+}
+
 export class PostHogFeatureFlags {
     _override_warning: boolean = false
     featureFlagEventHandlers: FeatureFlagsCallback[]
@@ -302,6 +307,15 @@ export class PostHogFeatureFlags {
                 }
 
                 this._flagsLoadedFromRemote = !errorsLoading
+
+                if (response.json && response.json.quotaLimited?.includes(QuotaLimitedResource.FeatureFlags)) {
+                    // log a warning and then early return
+                    logger.warn(
+                        'You have hit your feature flags quota limit, and will not be able to load feature flags until the quota is reset.  Please visit https://posthog.com/docs/billing/limits-alerts to learn more.'
+                    )
+                    return
+                }
+
                 this.receivedFeatureFlags(response.json ?? {}, errorsLoading)
 
                 if (this._additionalReloadRequested) {