fix: replace assertion with proper error handling

[nh13]

Summary

Replace assert() with proper error handling in generate_errors_flows().
Returns -1 with error message instead of crashing in release builds.

Closes #104

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Improved error handling to gracefully report processing failures with error codes instead of crashing, enabling better diagnostics and error recovery.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

📝 Walkthrough

Walkthrough

The change replaces an assertion in flow order lookup with explicit runtime error handling that logs an error message and returns -1 on failure, converting a hard abort into a recoverable error path.

Changes

Cohort / File(s)	Summary
Error Handling in Flow Order Lookup src/dwgsim.c	Replaced assert() with conditional check that prints error message and returns -1 when first non-N base is not found in flow order

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 A hop toward robustness true,
No more crashes—just a gentle "boo!"
Asserts are gone, now errors flow,
With grace and care, the code will grow. 🌟

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: replacing an assertion with proper error handling in the flow order lookup, which is the core objective of the PR.
Linked Issues check	✅ Passed	The PR successfully addresses issue #104 by replacing the assert() call with proper error handling that returns -1 and logs an error message instead of crashing.
Out of Scope Changes check	✅ Passed	All changes in src/dwgsim.c are directly related to replacing assertion with error handling as specified in issue #104; no out-of-scope modifications detected.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/assertion-error-handling

---

📜 Recent review details

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 26e3aa9 and 2408f1e.

📒 Files selected for processing (1)

• src/dwgsim.c

🔇 Additional comments (2)

src/dwgsim.c (2)

275-278: Excellent fix: proper error handling replaces assert().

Replacing the assert() with a runtime check and error return is a critical improvement. The original assert() would be compiled out in release builds (when NDEBUG is defined), causing undefined behavior if the first base isn't found in the flow order. The new code gracefully handles this edge case with an error message and a -1 return value.

---

275-278: The -1 return value is already being properly handled by the implicit check at line 878.

The callers at lines 854-855 assign the return value directly to s[j], which is then checked by if(s[j] <= 0) { continue; }. This correctly skips processing the read when an error occurs. The error condition itself is per-read (first base of the sequence not found in the flow order), so gracefully skipping that read is appropriate behavior. The error is also logged to stderr, providing visibility to the caller.

While the handling is correct, the implicit check could be made more explicit for clarity if desired, but no code changes are required.

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[nh13]

@coderabbitai review

[coderabbitai]

✅ Actions performed

Review triggered.

Note: CodeRabbit is an incremental review system and does not re-review already reviewed commits. This command is applicable only when automatic reviews are paused.