[Beginner]: Validate protobuf parsing in TopicId::fromBytes

[cheese-cakee]

🐥 Beginner Friendly

This issue is a great fit for contributors who are ready to explore the Hiero C++ codebase a little more and take on slightly more independent work.

Beginner Issues often involve reading existing C++ code, understanding how different parts of the SDK fit together, and making small, thoughtful updates that follow established patterns.

The goal is to support skill growth while keeping the experience approachable, well-scoped, and enjoyable.

Important

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---

👾 Description of the Task

TopicId::fromBytes() currently parses protobuf bytes without checking whether parsing succeeded.

Current implementation:

TopicId TopicId::fromBytes(const std::vector<std::byte>& bytes)
{
  proto::TopicID proto;
  proto.ParseFromArray(bytes.data(), static_cast<int>(bytes.size()));
  return fromProtobuf(proto);
}

If invalid bytes are provided, ParseFromArray(...) may fail and the function can still return a default/invalid-looking TopicId instead of failing fast.

Relevant files:

src/sdk/main/src/TopicId.cc
src/sdk/tests/unit/TopicIdUnitTests.cc

---

💡 Proposed Solution

Update TopicId::fromBytes() to validate the parse result and throw a clear std::invalid_argument when bytes cannot be parsed into proto::TopicID.

Also add a unit test that passes invalid bytes and verifies an exception is thrown.

This should be a narrow change:

• one production file (TopicId.cc)
• one unit test file (TopicIdUnitTests.cc)

---

👩‍💻 Implementation Steps

• Read src/sdk/main/src/TopicId.cc and locate TopicId::fromBytes()
• Update fromBytes() to check the return value of ParseFromArray(...)
• Throw std::invalid_argument with a descriptive message when parse fails
• Open src/sdk/tests/unit/TopicIdUnitTests.cc
• Add a unit test for invalid bytes that asserts TopicId::fromBytes(...) throws
• Confirm existing FromBytes happy-path test still passes
• Open a pull request with the changes

---

✅ Acceptance Criteria

• Scope: Changes are limited to src/sdk/main/src/TopicId.cc and src/sdk/tests/unit/TopicIdUnitTests.cc
• Behavior: Invalid bytes now throw std::invalid_argument in TopicId::fromBytes()
• Tests: New invalid-bytes unit test is added and passes; existing tests continue to pass
• Review: All code review feedback addressed

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📋 Step-by-Step Contribution Guide

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• Wait for assignment
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• Set up the project using the instructions in README.md
• Make the requested changes
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• Push your branch and open a pull request

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---

🤔 Additional Information

This improves SDK robustness by preventing silent fallback behavior on malformed input bytes.

If you have questions while working on this issue, feel free to ask!

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Whether you need help finding the right file, understanding existing code, or confirming your approach — we're happy to help.

[github-actions]

👋 Hi @HarK-github! This issue is not ready for development yet.

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[rwalworth]

Thanks for filing this, @cheese-cakee! The behavior you're describing is confirmed - ParseFromArray returns bool but the result is currently discarded, so invalid bytes silently produce a default TopicId(0, 0, 0). The fix is clear and well-scoped.

I'm going to classify this as a Beginner issue rather than Good First Issue however. The production change is straightforward, but the unit test requires some independent judgment - specifically, deciding how to construct invalid protobuf bytes and what the error message should say. Good First Issues should be fully scripted with no room for interpretation, so Beginner is the right fit here. I will also classify this as priority: low - there are no internal SDK callers passing invalid bytes here, so there's no current impact; it's a robustness improvement rather than a fix for something actively breaking.

[rwalworth]

/finalize

[github-actions]

✅ Issue finalized by @rwalworth!

Skill level: Beginner
Priority: priority: low

The issue body has been updated with the appropriate skill-level context and contribution guide. This issue is now ready for contributors to pick up via /assign.

[Gitjay11]

/assign