Add comprehensive error types and error handling

[Wetshakat]

closed #79

Add Comprehensive Error Types and Error Handling

Summary

Replaces all panic!(), .expect(), and untyped .unwrap() calls across every contract with
typed #[contracterror] error enums and Result return types. This gives callers
structured, machine-readable error codes instead of opaque panic strings.

Motivation

String-based panics make it impossible for frontend clients and integrators to
programmatically handle errors. Typed error enums with numeric codes allow:

• Frontend apps to match on specific error codes and show user-friendly messages
• Integration tests to assert on exact error variants
• Cross-contract callers to handle failures gracefully instead of catching panics

Changes by Contract

event_manager

5 new error variants added:

Code	Name	Replaces
11	EventNotCanceled	panic!("Event is not canceled")
12	RefundAlreadyClaimed	panic!("Refund already claimed")
13	NotABuyer	panic!("Claimer did not purchase a ticket")
14	EventSoldOut	panic!("Event is sold out")
15	TicketsBelowSold	panic!("Cannot reduce total_tickets below tickets_sold")

Functions converted to Result:

• claim_refund — was (), now Result<(), Error>
• update_event — was (), now Result<(), Error>
• purchase_ticket — was (), now Result<(), Error>

Also removed a dangling duplicate panic!("Ticket factory not initialized") line in
deploy_ticket_nft helper.

ticket_nft

1 new error variant:

Code	Name	Replaces
5	NotInitialized	.unwrap() / .expect("Not initialized")

Functions converted to Result:

• burn — was (), now Result<(), Error>
• get_minter — was Address, now Result<Address, Error>
• mint_ticket_nft — internal .unwrap() replaced with ?

tba_registry

1 new error variant:

Code	Name	Replaces
2	NotInitialized	.expect("Registry not initialized")

Changed in create_account: .expect() → .ok_or(Error::NotInitialized)?

ticket_factory

Entirely new Error enum (contract had none):

Code	Name	Description
1	NotInitialized	Storage not set (pre-constructor)
2	Unauthorized	Caller is not admin

Functions converted to Result:

• deploy_ticket — was Address, now Result<Address, Error>
• get_admin — was Address, now Result<Address, Error>

tba_account

No changes needed — already used typed errors throughout.

Test Updates

• event_manager/src/lib.rs (update_event_tests): 5 #[should_panic] tests → try_
  assertions
• event_manager/src/test.rs: 5 #[should_panic] tests → try_ assertions
• ticket_factory/src/test.rs: Added .unwrap() to 8 deploy_ticket, 1 get_admin, 1
  get_minter calls

Files Changed

File	Changes
soroban-contract/contracts/event_manager/src/lib.rs	5 new errors, 3 functions →
Result, 17 panics removed
soroban-contract/contracts/event_manager/src/test.rs	5 tests converted from should_
panic to try_
soroban-contract/contracts/ticket_nft/src/lib.rs	1 new error, 2 functions → Result,
1 unwrap removed
soroban-contract/contracts/tba_registry/src/lib.rs	1 new error, 1 expect removed
soroban-contract/contracts/ticket_factory/src/lib.rs	New Error enum, 2 functions →
Result, 3 unwraps removed
soroban-contract/contracts/ticket_factory/src/test.rs	10 calls updated with .unwrap(
)

How to Verify

1. Check that zero panic!(), .expect(), or untyped .unwrap() calls remain in any
   contract's non-test code
2. All #[should_panic] tests have been converted (except 2 legitimate auth-failure tests
   in ticket_nft and tba_account)
3. Error codes are sequential and unique within each contract

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You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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