Refactor session manager item equality

[riatzukiza]

Summary

• add itemsEqual helper to safely stringify items once
• replace duplicate JSON.stringify comparisons in prefix/suffix checks
• document scope in spec/session-manager-items-equality.md

Testing

• npm test -- session-manager.test.ts

[coderabbitai]

Summary by CodeRabbit

• Chores
  • Enhanced session management robustness with improved error handling and fallback mechanisms.

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Walkthrough

Adds an internal itemsEqual() helper that safely compares two InputItem values using guarded JSON serialization; wraps computeHash(items) with a try/catch fallback and replaces direct JSON.stringify equality checks in longestSharedPrefixLength() and findSuffixReuseStart() with itemsEqual() calls.

Changes

Cohort / File(s)	Summary
Session manager refactor lib/session/session-manager.ts	Add internal itemsEqual() helper (try/catch JSON compare); wrap computeHash(items) with a guarded fallback; replace direct JSON.stringify equality checks in longestSharedPrefixLength() and findSuffixReuseStart() with itemsEqual()

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

• Focus review on itemsEqual() correctness and its failure semantics.
• Verify computeHash(items) fallback preserves deterministic behavior and doesn't widen collision risk.
• Confirm call sites (longestSharedPrefixLength, findSuffixReuseStart) maintain prior logic when itemsEqual() falls back to false.

Poem

A tiny guard to mend the crack,
JSON trips no longer stack,
Items compared with cautious grace,
Session logic finds its place. ✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'Refactor session manager item equality' directly and clearly describes the main change: adding an itemsEqual helper and refactoring equality comparisons in the session manager.
Description check	✅ Passed	The description is directly related to the changeset, outlining the key modifications (itemsEqual helper, replacing duplicate comparisons, documenting in spec) and specifying tests to run.

✨ 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 session-items-equal-helper

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📜 Recent review details

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Review profile: ASSERTIVE

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📥 Commits

Reviewing files that changed from the base of the PR and between 2478ca2 and 9a8b3e0.

📒 Files selected for processing (1)

• lib/session/session-manager.ts (3 hunks)

🧰 Additional context used

🧬 Code graph analysis (1)

lib/session/session-manager.ts (1)

lib/types.ts (1)

• InputItem (148-154)

🔇 Additional comments (3)

lib/session/session-manager.ts (3)

18-24: LGTM! Addresses past review feedback.

The try-catch wrapper is now consistent with itemsEqual and fingerprintInputItem. The fallback hash using item count is deterministic and appropriate. While theoretically two non-serializable arrays of the same length would collide, this is acceptable given that InputItem arrays are typically serializable.

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26-32: LGTM! Clean refactoring that reduces duplication.

The itemsEqual helper centralizes the JSON.stringify comparison logic and provides consistent error handling. The function correctly handles undefined inputs and returns false on serialization failures, which is a safe default.

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43-43: LGTM! Correct usage of the helper.

Both replacements correctly delegate to itemsEqual instead of performing inline JSON.stringify comparisons. Array bounds are properly guarded in both functions, so the refactoring is safe.

Also applies to: 110-110

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[coderabbitai]

Actionable comments posted: 1

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

lib/session/session-manager.ts (1)

18-20: Consider adding error handling to computeHash for consistency.

Similar to the new itemsEqual and existing fingerprintInputItem, this function serializes InputItem data and could encounter circular references or other serialization failures. The inconsistency means computeHash could throw while other serialization points handle errors gracefully.

Apply this diff to add consistent error handling:

 function computeHash(items: InputItem[]): string {
-	return createHash("sha1").update(JSON.stringify(items)).digest("hex");
+	try {
+		return createHash("sha1").update(JSON.stringify(items)).digest("hex");
+	} catch {
+		// Fallback for non-serializable content
+		return createHash("sha1").update(randomUUID()).digest("hex");
+	}
 }

📜 Review details

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 208d9d2 and 2478ca2.

⛔ Files ignored due to path filters (1)

• spec/session-manager-items-equality.md is excluded by none and included by none

📒 Files selected for processing (1)

• lib/session/session-manager.ts (3 hunks)

🧰 Additional context used

🧬 Code graph analysis (1)

lib/session/session-manager.ts (1)

lib/types.ts (1)

• InputItem (148-154)

🔇 Additional comments (2)

lib/session/session-manager.ts (2)

39-39: LGTM!

Clean replacement that centralizes the comparison logic and adds error handling.

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106-106: LGTM!

Consistent application of the new helper improves maintainability.