Add Comprehensive Error Handling & Custom Error Types

[OthmanImam]

Context

Currently, contract functions panic on invalid inputs or edge cases. This creates poor UX and makes debugging difficult for frontend integration. We need structured error types that communicate specific failure reasons to callers.

Problem

• No custom error types defined; functions use unwrap() which panics
• Frontend cannot distinguish between different failure modes (invalid token, insufficient balance, swap validation failure)
• Error messages are unhelpful for debugging or user-facing UI

What "Done" Looks Like

• Define a custom ContractError enum covering all failure modes:
  • Invalid token symbol
  • Insufficient balance
  • Invalid swap pair
  • Zero amount swap attempt
  • Unauthorized access
• Replace all unwrap() calls with proper Result<T, ContractError>
• Update all public contract functions to return Result types
• Add comprehensive test cases for each error path in swaptrade-contracts/counter/src/

Implementation Guidelines

• Define error enum in a new errors.rs module
• Use Soroban's Result with custom error mapping
• Ensure error types serialize properly for contract invocation responses
• Reference: Soroban error handling docs
• Watch for: Panic paths in trading.rs and portfolio.rs logic

Acceptance Criteria

• ContractError enum implemented with 5+ error variants
• All public functions return Result<T, ContractError> (0 unwrap() calls in public API)
• Error types serialize/deserialize correctly for Soroban contract responses
• Test suite has 100% coverage of error paths
• All error variants tested with expected contract failure modes
• Documentation clearly explains each error type and when it occurs

Validation

• All tests pass with new error handling
• No panics occur on invalid inputs (test with malformed data)
• Error enum variants are clearly documented

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[Emmyt24]

@Emmyt24 has applied to work on this issue as part of the Stellar Wave Program's 1st wave.

I’d like to take on this error-handling upgrade task, I’ll introduce a ContractError enum in errors.rs, replace panic/unwrap paths with Result<T, ContractError> across the public API (especially trading.rs and portfolio.rs), and add full tests to cover each error variant and ensure Soroban-compatible serialization.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Emmyt24 to this issue.

[Alsnj20]

@Alsnj20 has applied to work on this issue as part of the Stellar Wave Program's 1st wave.

Hi, I would like to take this task. I will add a ContractError enum in errors.rs, update the public API to return Result<T, ContractError> (including trading.rs, portfolio.rs, and lib.rs), replace unwrap() with proper error handling, make sure errors are correctly serialized for Soroban, and add unit tests to cover all error cases and verify the expected contract behavior. My response time may be up to 4 hours.

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[gelluisaac]

@gelluisaac has applied to work on this issue as part of the Stellar Wave Program's 1st wave.

I’m a software and blockchain developer experienced in debugging complex systems, writing secure smart contracts, and optimizing backend logic. I enjoy tackling open issues, improving performance, and contributing meaningful, production-ready solutions. Looking forward to collaborating on this issue.

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[chizzy192]

@chizzy192 has applied to work on this issue as part of the Stellar Wave Program's 1st wave.

Hello, I'm Chiziterem, and I'd love to work on issue #27. I would love to work on the form handling that involves error handling and error types. Thank you!

ℹ️ Repo Maintainers: To accept this application, review their application or assign @chizzy192 to this issue.

[lishmanTech]

@lishmanTech has applied to work on this issue as part of the Stellar Wave Program's 1st wave.

Hello maintainer

I would love to work on this issue

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Congratulations, @lishmanTech! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on January 31, 2026.

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This issue has been completed by @lishmanTech as part of the Stellar Wave Program's 1st Wave 🥳

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@lishmanTech received 4 compliments:

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