fix(app): gate single-source message hover behind an experiment (#2761)

packages/schema/src/domains/admin/AdminSchemas.ts

@@ -23,6 +23,10 @@ import {
 	ExperimentDeliveryConfigResponse,
 	ExperimentDeliveryConfigUpdateRequest,
 } from '@fluxer/schema/src/domains/experiment/ExperimentSchemas';
+import {
+	MessageHoverTrackingConfigResponse,
+	MessageHoverTrackingConfigUpdateRequest,
+} from '@fluxer/schema/src/domains/experiment/MessageHoverTrackingSchemas';
 import {GuildMemberResponse} from '@fluxer/schema/src/domains/guild/GuildMemberSchemas';
 import {
 	InstanceCaptchaProviderSchema,
@@ -630,6 +634,7 @@ export const InstanceConfigResponse = z.object({
 	gateway_rollout: GatewayRolloutConfigResponse,
 	voice_noise_suppression: VoiceNoiseSuppressionConfigResponse,
 	experiment_delivery: ExperimentDeliveryConfigResponse,
+	message_hover_tracking: MessageHoverTrackingConfigResponse,
 	registration: InstanceRegistrationResponse,
 	self_hosted: z.boolean(),
 	app_public: AppPublicConfigResponse,
@@ -666,6 +671,7 @@ export const InstanceConfigUpdateRequest = z.object({
 	gateway_rollout: GatewayRolloutConfigUpdateRequest.nullish(),
 	voice_noise_suppression: VoiceNoiseSuppressionConfigUpdateRequest.nullish(),
 	experiment_delivery: ExperimentDeliveryConfigUpdateRequest.nullish(),
+	message_hover_tracking: MessageHoverTrackingConfigUpdateRequest.nullish(),
 	registration: z
 		.object({
 			mode: InstanceRegistrationModeSchema.optional(),

packages/schema/src/domains/experiment/ClientBehaviorExperiment.ts

@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+import {EXPERIMENT_BUCKET_RESOLUTION, experimentBucket} from '@fluxer/schema/src/domains/experiment/ExperimentBucket';
+import {z} from 'zod';
+
+const CLIENT_BEHAVIOR_MAX_TARGETED_USERS = 1000;
+const CLIENT_BEHAVIOR_ASSIGNMENT_SOURCES = ['user_rule', 'canary'] as const;
+
+export function createClientBehaviorExperiment({defaultRolloutSalt}: {defaultRolloutSalt: string}) {
+	const targetIdSchema = z.string().regex(/^\d{1,20}$/u);
+	const targetedUserIdsSchema = z.array(targetIdSchema).max(CLIENT_BEHAVIOR_MAX_TARGETED_USERS);
+	const configFields = {
+		enabled: z.boolean(),
+		config_version: z.number().int().min(0),
+		rollout_basis_points: z.number().int().min(0).max(EXPERIMENT_BUCKET_RESOLUTION),
+		rollout_salt: z.string().trim().min(1).max(64),
+		included_user_ids: targetedUserIdsSchema,
+		excluded_user_ids: targetedUserIdsSchema,
+	};
+	const ConfigSchema = z.object({
+		enabled: configFields.enabled.default(false),
+		config_version: configFields.config_version.default(0),
+		rollout_basis_points: configFields.rollout_basis_points.default(0),
+		rollout_salt: configFields.rollout_salt.default(defaultRolloutSalt),
+		included_user_ids: configFields.included_user_ids.default([]),
+		excluded_user_ids: configFields.excluded_user_ids.default([]),
+	});
+	const ConfigUpdateRequest = z.object(configFields).omit({config_version: true}).partial();
+	const AssignmentResponse = z.object({
+		enabled: configFields.enabled,
+		config_version: z.number().int(),
+		user_targeted: z.boolean(),
+		source: z.enum(CLIENT_BEHAVIOR_ASSIGNMENT_SOURCES).nullable(),
+	});
+	type Config = z.infer<typeof ConfigSchema>;
+	type Assignment = z.infer<typeof AssignmentResponse>;
+	const DEFAULT_CONFIG: Config = ConfigSchema.parse({});
+	const INERT_ASSIGNMENT: Assignment = {
+		enabled: false,
+		config_version: 0,
+		user_targeted: false,
+		source: null,
+	};
+	const resolveAssignment = (config: Config, userId: string): Assignment => {
+		if (!config.enabled) {
+			return {...INERT_ASSIGNMENT, config_version: config.config_version};
+		}
+		const shared = {enabled: true, config_version: config.config_version};
+		if (config.excluded_user_ids.includes(userId)) {
+			return {...shared, user_targeted: false, source: null};
+		}
+		if (config.included_user_ids.includes(userId)) {
+			return {...shared, user_targeted: true, source: 'user_rule'};
+		}
+		const inCanary = experimentBucket(userId, config.rollout_salt) < config.rollout_basis_points;
+		return {...shared, user_targeted: inCanary, source: inCanary ? 'canary' : null};
+	};
+	return {ConfigSchema, ConfigUpdateRequest, AssignmentResponse, DEFAULT_CONFIG, INERT_ASSIGNMENT, resolveAssignment};
+}

packages/schema/src/domains/experiment/ExperimentSchemas.ts

@@ -4,6 +4,10 @@ import {
 	INERT_VOICE_NOISE_SUPPRESSION_ASSIGNMENT,
 	VoiceNoiseSuppressionAssignmentResponse,
 } from '@fluxer/schema/src/domains/admin/VoiceNoiseSuppressionSchemas';
+import {
+	INERT_MESSAGE_HOVER_TRACKING_ASSIGNMENT,
+	MessageHoverTrackingAssignmentResponse,
+} from '@fluxer/schema/src/domains/experiment/MessageHoverTrackingSchemas';
 import {z} from 'zod';
 
 export const EXPERIMENT_MIN_POLL_INTERVAL_SECONDS = 60;
@@ -42,6 +46,7 @@ export type ExperimentDeliveryConfigResponse = z.infer<typeof ExperimentDelivery
 
 const ExperimentAssignmentsSchema = z.object({
 	voice_noise_suppression: VoiceNoiseSuppressionAssignmentResponse.optional(),
+	message_hover_tracking: MessageHoverTrackingAssignmentResponse.optional(),
 });
 
 export const ExperimentAssignmentsResponse = z.object({
@@ -63,3 +68,9 @@ export function readVoiceNoiseSuppressionAssignment(
 ): VoiceNoiseSuppressionAssignmentResponse {
 	return response.assignments.voice_noise_suppression ?? INERT_VOICE_NOISE_SUPPRESSION_ASSIGNMENT;
 }
+
+export function readMessageHoverTrackingAssignment(
+	response: ExperimentAssignmentsResponse,
+): MessageHoverTrackingAssignmentResponse {
+	return response.assignments.message_hover_tracking ?? INERT_MESSAGE_HOVER_TRACKING_ASSIGNMENT;
+}

packages/schema/src/domains/experiment/MessageHoverTrackingSchemas.ts

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+import {createClientBehaviorExperiment} from '@fluxer/schema/src/domains/experiment/ClientBehaviorExperiment';
+import type {z} from 'zod';
+
+const messageHoverTracking = createClientBehaviorExperiment({defaultRolloutSalt: 'message-hover-tracking-v1'});
+
+export const MessageHoverTrackingConfigSchema = messageHoverTracking.ConfigSchema;
+
+export type MessageHoverTrackingConfig = z.infer<typeof MessageHoverTrackingConfigSchema>;
+
+export const DEFAULT_MESSAGE_HOVER_TRACKING_CONFIG: MessageHoverTrackingConfig = messageHoverTracking.DEFAULT_CONFIG;
+
+export const MessageHoverTrackingConfigUpdateRequest = messageHoverTracking.ConfigUpdateRequest;
+
+export type MessageHoverTrackingConfigUpdateRequest = z.infer<typeof MessageHoverTrackingConfigUpdateRequest>;
+
+export const MessageHoverTrackingConfigResponse = messageHoverTracking.ConfigSchema;
+
+export type MessageHoverTrackingConfigResponse = MessageHoverTrackingConfig;
+
+export const MessageHoverTrackingAssignmentResponse = messageHoverTracking.AssignmentResponse;
+
+export type MessageHoverTrackingAssignmentResponse = z.infer<typeof MessageHoverTrackingAssignmentResponse>;
+
+export const INERT_MESSAGE_HOVER_TRACKING_ASSIGNMENT: MessageHoverTrackingAssignmentResponse =
+	messageHoverTracking.INERT_ASSIGNMENT;
+
+export function resolveMessageHoverTrackingAssignment(
+	config: MessageHoverTrackingConfig,
+	userId: string,
+): MessageHoverTrackingAssignmentResponse {
+	return messageHoverTracking.resolveAssignment(config, userId);
+}

packages/schema/src/domains/tests/MessageHoverTrackingSchemas.test.ts

@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+import {EXPERIMENT_BUCKET_RESOLUTION, experimentBucket} from '@fluxer/schema/src/domains/experiment/ExperimentBucket';
+import {
+	DEFAULT_MESSAGE_HOVER_TRACKING_CONFIG,
+	MessageHoverTrackingConfigSchema,
+	resolveMessageHoverTrackingAssignment,
+} from '@fluxer/schema/src/domains/experiment/MessageHoverTrackingSchemas';
+import {describe, expect, it} from 'vitest';
+
+const USER_ID = '1485064866382176262';
+const OTHER_USER_ID = '1485064866382176263';
+
+function config(overrides: Partial<ReturnType<typeof MessageHoverTrackingConfigSchema.parse>> = {}) {
+	return MessageHoverTrackingConfigSchema.parse({...overrides});
+}
+
+describe('message hover tracking configuration', () => {
+	it('defaults to a disabled rollout that targets nobody', () => {
+		expect(DEFAULT_MESSAGE_HOVER_TRACKING_CONFIG).toEqual({
+			enabled: false,
+			config_version: 0,
+			rollout_basis_points: 0,
+			rollout_salt: 'message-hover-tracking-v1',
+			included_user_ids: [],
+			excluded_user_ids: [],
+		});
+	});
+
+	it('refuses a rollout wider than the bucket resolution', () => {
+		expect(() => config({rollout_basis_points: EXPERIMENT_BUCKET_RESOLUTION + 1})).toThrow();
+	});
+
+	it('refuses a target that is not a snowflake', () => {
+		expect(() => config({included_user_ids: ['not-a-snowflake']})).toThrow();
+	});
+});
+
+describe('message hover tracking resolution', () => {
+	it('reports the stored revision while the rollout is disabled', () => {
+		const assignment = resolveMessageHoverTrackingAssignment(config({config_version: 3}), USER_ID);
+		expect(assignment).toEqual({enabled: false, config_version: 3, user_targeted: false, source: null});
+	});
+
+	it('targets an allowlisted account regardless of its bucket', () => {
+		const assignment = resolveMessageHoverTrackingAssignment(
+			config({enabled: true, included_user_ids: [USER_ID]}),
+			USER_ID,
+		);
+		expect(assignment).toEqual({enabled: true, config_version: 0, user_targeted: true, source: 'user_rule'});
+	});
+
+	it('keeps a blocklisted account out of a full rollout', () => {
+		const assignment = resolveMessageHoverTrackingAssignment(
+			config({
+				enabled: true,
+				rollout_basis_points: EXPERIMENT_BUCKET_RESOLUTION,
+				excluded_user_ids: [USER_ID],
+			}),
+			USER_ID,
+		);
+		expect(assignment).toEqual({enabled: true, config_version: 0, user_targeted: false, source: null});
+	});
+
+	it('prefers the blocklist over the allowlist', () => {
+		const assignment = resolveMessageHoverTrackingAssignment(
+			config({enabled: true, included_user_ids: [USER_ID], excluded_user_ids: [USER_ID]}),
+			USER_ID,
+		);
+		expect(assignment.user_targeted).toBe(false);
+	});
+
+	it('targets an account whose bucket falls inside the rollout', () => {
+		const salt = DEFAULT_MESSAGE_HOVER_TRACKING_CONFIG.rollout_salt;
+		const bucket = experimentBucket(USER_ID, salt);
+		const inside = resolveMessageHoverTrackingAssignment(
+			config({enabled: true, rollout_basis_points: bucket + 1}),
+			USER_ID,
+		);
+		const outside = resolveMessageHoverTrackingAssignment(
+			config({enabled: true, rollout_basis_points: bucket}),
+			USER_ID,
+		);
+		expect(inside).toEqual({enabled: true, config_version: 0, user_targeted: true, source: 'canary'});
+		expect(outside).toEqual({enabled: true, config_version: 0, user_targeted: false, source: null});
+	});
+
+	it('separates two accounts under the same salt', () => {
+		const salt = DEFAULT_MESSAGE_HOVER_TRACKING_CONFIG.rollout_salt;
+		expect(experimentBucket(USER_ID, salt)).not.toBe(experimentBucket(OTHER_USER_ID, salt));
+	});
+
+	it('moves an account when the salt changes', () => {
+		expect(experimentBucket(USER_ID, 'message-hover-tracking-v1')).not.toBe(
+			experimentBucket(USER_ID, 'message-hover-tracking-v2'),
+		);
+	});
+});