🐛 Fix race condition in lambda.register with once option

[Milly]

Ensure the lambda is unregistered before invoking the function when once option is specified, preventing multiple concurrent calls from executing the function more than once.

Update test to cover the case where the lambda is called multiple times before the first call resolves.

Summary by CodeRabbit

• Refactor

  • Updated internal logic for unregistering one-time lambda functions to unregister before execution begins.

• Tests

  • Improved tests for one-time lambda function registration to better handle asynchronous behavior and error scenarios.

• Chores

  • Added a new import mapping for "@core/asyncutil" in configuration.

[coderabbitai]

Walkthrough

A new import alias for @core/asyncutil was added to the configuration. The lambda registration logic was changed to unregister the lambda before invoking its function instead of after. The related test was updated to handle asynchronous resolution more explicitly and to verify lambda removal behavior using the promise from the second call.

Changes

File(s)	Change Summary
deno.jsonc	Added "@core/asyncutil" import alias pointing to "jsr:@core/asyncutil@^1.2.0".
lambda/mod.ts	Changed lambda unregister logic to occur before awaiting the function, removing try-finally.
lambda/mod_test.ts	Updated test to handle async lambda resolution and verify removal using the second call's promise.

Poem

In the land of lambdas, swift and bright,
Unregister comes before the flight.
Async promises now take their turn,
While rabbits watch and tests discern.
A new import hops into view—
Code grows stronger, fresh and new!
🐇✨

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📜 Recent review details

Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 5f8e7f4 and cc169d1.

📒 Files selected for processing (3)

• deno.jsonc (1 hunks)
• lambda/mod.ts (1 hunks)
• lambda/mod_test.ts (2 hunks)

⏰ Context from checks skipped due to timeout of 90000ms (6)

• GitHub Check: test (macos-latest, 1.x, v9.1.0448, v0.10.0)
• GitHub Check: test (windows-latest, 1.x, v9.1.0448, v0.10.0)
• GitHub Check: test (ubuntu-latest, 1.45.0, v9.1.0448, v0.10.0)
• GitHub Check: test (windows-latest, 1.45.0, v9.1.0448, v0.10.0)
• GitHub Check: test (macos-latest, 1.45.0, v9.1.0448, v0.10.0)
• GitHub Check: test (ubuntu-latest, 1.x, v9.1.0448, v0.10.0)

🔇 Additional comments (4)

deno.jsonc (1)

50-50: LGTM! Required dependency for test utilities.

The addition of @core/asyncutil import mapping is necessary for the flushPromises utility used in the updated tests to properly handle asynchronous operations.

lambda/mod.ts (1)

123-124: Excellent fix for the race condition!

Moving the unregister() call before function execution is the correct solution. This ensures that even if multiple concurrent calls are made, only the first one will execute the function since subsequent calls will find the lambda already removed from the dispatcher.

lambda/mod_test.ts (2)

9-9: Good addition of required test utility.

The flushPromises import is necessary for the updated test to properly handle asynchronous timing and ensure microtasks are processed before assertions.

---

76-98: Excellent test coverage for the race condition fix!

This test properly simulates the race condition scenario:

1. Promise control: Uses Promise.withResolvers() to create a lambda that won't resolve until manually triggered
2. Concurrent calls: Makes two calls before resolution to simulate the race condition
3. Proper timing: Uses flushPromises() to ensure microtasks are processed before resolving
4. Comprehensive assertions: Verifies the first call succeeds, function is called only once, and second call properly rejects

This is a significant improvement over sequential testing and actually validates the fix works correctly.

✨ Finishing Touches

• 📝 Generate Docstrings

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.78%. Comparing base (5f8e7f4) to head (cc169d1).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #282      +/-   ##
==========================================
- Coverage   85.80%   85.78%   -0.02%     
==========================================
  Files          65       65              
  Lines        3458     3455       -3     
  Branches      301      301              
==========================================
- Hits         2967     2964       -3     
  Misses        489      489              
  Partials        2        2              

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[lambdalisue]

LGTM. Thanks