Improve Type Safety in event.ts and Remove Remaining `any` Usage

[Harxhit]

Summary

Improve type safety in event.ts by removing remaining usages of any and replacing them with proper Fastify, TypeScript, Prisma, and application-specific types.

Contexts

The event routes currently contain several usages of any that bypass TypeScript's type checking and reduce maintainability.

Examples include:

const server = request.server as any;

(app as any).authenticate

(request.user as any).id

catch (error: any)

Some of these usages are related to authentication, Fastify route handlers, and Prisma error handling. Existing shared Fastify/JWT type definitions should be reused where available instead of introducing duplicate definitions.

Removing these usages will improve maintainability, reduce unsafe casts, and make future refactoring easier.

Tasks

• Identify all remaining any usages in event.ts
• Use existing Fastify/JWT type definitions where available
• Replace server as any with appropriate Fastify types
• Replace app as any with appropriate Fastify types
• Replace request.user as any with properly typed user access
• Replace error: any with safer error handling patterns
• Improve authentication-related typing where applicable
• Verify TypeScript passes without introducing new type errors
• Update tests if required

Acceptance Criteria

• No any usages remain in event.ts
• Existing shared Fastify/JWT types are reused where applicable
• Authenticated user access is properly typed
• Authentication-related code uses proper Fastify types
• Error handling avoids unsafe any usage
• TypeScript checks pass successfully
• Existing event functionality continues to work
• Tests pass successfully

Area

backend

Difficulty

Good First Issue

[github-actions]

Hi @Harxhit,

Thanks for opening this issue.

Please reply with one of the following areas so the issue can be routed to the appropriate team member:

- /backend
- /web
- /mobile
- /devops

Once an area is selected, the corresponding label will be added automatically.

[Harxhit]

/backend

[github-actions]

The issue has been classified as backend.

@Harxhit, please review and triage this issue when available.

The backend label has been applied and the issue has been routed accordingly.

[Srejoye]

1. Preauth boilerplate (lines 62, 64, 156, 190) — request.server as any / (app as any).authenticate, used across the POST /, POST /:slug/join, and DELETE /:slug/leave handlers, in the same 3-branch defensive form as follow.ts.
2. (request.user as any).id (lines 75, 157, 191) — same FastifyJWT gap as the other type-safety issues in this batch.
3. catch (error: any) (lines 180, 214) — both in eventAttendee mutation handlers (join/leave), checking error.code === 'P2002' / 'P2025' respectively for Prisma constraint/not-found errors.

Proposed fix approach:

• Reuse the shared FastifyJWT payload/user augmentation (src/types/fastify.d.ts, { id: string; username: string }) introduced for Improve Type Safety in profiles.ts and Remove Remaining any Usage #552/Improve Type Safety in public.ts and Remove Remaining any Usage #553/Improve Type Safety in team.ts and Remove Remaining any Usage #554/Improve Type Safety in follow.ts and Remove Remaining any Usage #550 to resolve all 3 (request.user as any).id casts.
• Collapse the preHandler boilerplate to app.authenticate, consistent with the other three route files in this batch.
• For the two catch (error: any) blocks: switch to catch (error: unknown) and narrow with error instanceof Prisma.PrismaClientKnownRequestError before checking .code — Prisma is already importable here (used elsewhere for TeamRole/Prisma in team.ts, and the pattern is established there for P2002/P2003). This correctly types error.code access for both the P2002 (join, duplicate attendee) and P2025 (leave, record-not-found) checks, while app.log.error((error as Error).message) becomes app.log.error(getErrorMessage(error)) if the shared getErrorMessage helper (already used in follow.ts/connect.ts) is reused, or kept as a safe instanceof Error check.

Affected files: apps/backend/src/routes/event.ts, apps/backend/src/types/fastify.d.ts (shared augmentation, reused across the batch).

Test considerations: Pure typing/narrowing refactor. Confirm __tests__/event.test.ts still passes for: duplicate-join → 409 "Already joined" (P2002 path), leave-when-not-joined → 404 "User not found" (P2025 path), and the 401 path for unauthenticated POST /:slug/join / DELETE /:slug/leave. tsc --noEmit should show zero any in this file with no new errors from the shared augmentation.

I'd like to take this under GSSoC'26.

[Harxhit]

@Srejoye I have assigned this issue to you.