[DoctorGuidance]

Summary

Fixes #2034.

In the Bun adapter, listen() registers an anonymous process.on('beforeExit', ...) listener that closes over app. Previously, stop() never removed this listener. As a result:

1. Stopped app instances (and everything reachable from them: routes, plugins, stores) were held alive in memory via process listeners for the entire lifetime of the process.
2. When starting and stopping apps in succession (such as test suites or server lifecycle swapping), each listen() added another listener, eventually triggering a MaxListenersExceededWarning (past 10 listeners).

Changes

1. src/adapter/bun/index.ts:
   • Track active beforeExit listeners per app using a file-scoped WeakMap<AnyElysia, () => Promise<void>>.
   • Clear any previous listener before registering if listen() is called again on the same app.
   • Remove the listener from process and clear the WeakMap entry when app.stop() is called or when beforeExit executes.
2. test/core/stop.test.ts:
   • Added unit test asserting that process.listeners('beforeExit') increments on listen(0) and returns to its baseline count upon server.stop().

Summary by CodeRabbit

• Bug Fixes
  • Server shutdown and repeated starts now clean up exit handling consistently, preventing stale handlers from accumulating and ensuring the active server stops as expected.

[coderabbitai]

Walkthrough

The Bun adapter now tracks each app’s beforeExit handler, replaces it on repeated listen() calls, and removes it during stop() or when it runs. A test checks that stopping the server restores the original listener count.

Changes

Bun listener lifecycle

Layer / File(s)	Summary
Track and clean up beforeExit handlers src/adapter/bun/index.ts, test/core/stop.test.ts	The adapter stores each app’s beforeExit handler in a WeakMap. It replaces an existing handler when the same app listens again, and removes the handler when the app stops or the handler runs. The test checks that server.stop() returns the listener count to its starting value.

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Medium

Possibly related PRs

• elysiajs/elysia#2035 — This PR also tracks and removes Bun beforeExit handlers, and changes overlapping stop behavior.

Suggested reviewers: saltyaom

Merge Risk: Low · up to b9b24

The listener cleanup is supported by the inspected implementation. This is mergeable with a bounded testing follow-up: cover repeated listen calls so future changes cannot silently reintroduce listener accumulation.

Pre-merge checks: 5

Check name	Status	Explanation
Title check		The title clearly identifies the main change: removing the Bun adapter's process beforeExit listener when the server stops.
Description check		The description explains the issue, impact, implementation, linked issue, and regression test. It does not reproduce the template headings or prerequisite checkboxes, but it contains the main informat…
Linked Issues check		The changes satisfy the coding requirements in issue #2034. src/adapter/bun/index.ts stores each app's beforeExit handler in a WeakMap, removes an existing handler before re-registering, and rem…
Out of Scope Changes check		The reviewed changes remain within issue #2034. The WeakMap lifecycle handling directly fixes the Bun adapter listener leak. The listener-count test supports that behavior. No unrelated production b…
Docstring Coverage		No eligible functions found in the changed files. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentat…

Full details: Description check

Explanation

The description explains the issue, impact, implementation, linked issue, and regression test. It does not reproduce the template headings or prerequisite checkboxes, but it contains the main information required for review.

Full details: Linked Issues check

Explanation

The changes satisfy the coding requirements in issue #2034. src/adapter/bun/index.ts stores each app's beforeExit handler in a WeakMap, removes an existing handler before re-registering, and removes the handler during stop() and handler execution. The test in test/core/stop.test.ts verifies that server.stop() restores the baseline beforeExit listener count. These changes address listener accumulation and release the process reference to stopped apps. PASS, nicely done~ ♡ (￣▽￣)

Full details: Out of Scope Changes check

Explanation

The reviewed changes remain within issue #2034. The WeakMap lifecycle handling directly fixes the Bun adapter listener leak. The listener-count test supports that behavior. No unrelated production behavior or unrelated test change is evident. Try not to celebrate too much, okay~ (¬‿¬)♡

Full details: Docstring Coverage

Explanation

No eligible functions found in the changed files. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 0 functions across 2 files.

Finishing Touches

Generate unit tests (beta)

• Create a new PR

• Autofix · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

Warning

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ESLint

If the error stems from missing dependencies, add them to the package.json file. For unrecoverable errors (e.g., due to private dependencies), disable the tool in the CodeRabbit configuration.

src/adapter/bun/index.ts

Oops! Something went wrong! :(

ESLint: 9.39.5

Error: ESLint configuration in --config » plugin:sonarjs/recommended is invalid:

• Unexpected top-level property "name".

Referenced from: /.eslintrc.json
at ConfigValidator.validateConfigSchema (/.eslint-tmp/node_modules/.pnpm/@eslint+eslintrc@3.3.7_supports-color@7.2.0/node_modules/@eslint/eslintrc/dist/eslintrc.cjs:2277:19)
at ConfigArrayFactory._normalizeConfigData (/.eslint-tmp/node_modules/.pnpm/@eslint+eslintrc@3.3.7_supports-color@7.2.0/node_modules/@eslint/eslintrc/dist/eslintrc.cjs:3123:19)
at ConfigArrayFactory._loadExtendedPluginConfig (/.eslint-tmp/node_modules/.pnpm/@eslint+eslintrc@3.3.7_supports-color@7.2.0/node_modules/@eslint/eslintrc/dist/eslintrc.cjs:3346:25)
at ConfigArrayFactory._loadExtends (/.eslint-tmp/node_modules/.pnpm/@eslint+eslintrc@3.3.7_supports-color@7.2.0/node_modules/@eslint/eslintrc/dist/eslintrc.cjs:3259:29)
at ConfigArrayFactory._normalizeObjectConfigDataBody (/.eslint-tmp/node_m

... [truncated 555 characters] ...

st/eslintrc.cjs:2952:16)
at createCLIConfigArray (/.eslint-tmp/node_modules/.pnpm/@eslint+eslintrc@3.3.7_supports-color@7.2.0/node_modules/@eslint/eslintrc/dist/eslintrc.cjs:3768:35)
(node:2) ESLintRCWarning: You are using an eslintrc configuration file, which is deprecated and support will be removed in v10.0.0. Please migrate to an eslint.config.js file. See https://eslint.org/docs/latest/use/configure/migration-guide for details. An eslintrc configuration file is used because you have the ESLINT_USE_FLAT_CONFIG environment variable set to false. If you want to use an eslint.config.js file, remove the environment variable. If you want to find the location of the eslintrc configuration file, use the --debug flag.
(Use node --trace-warnings ... to show where the warning was created)

test/core/stop.test.ts

ESLint skipped: the matched ESLint configuration already failed (config-incompatibility).

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_{One handler joins the process line ♡
A WeakMap keeps its place in view~
Stop says “go,” and clears it clean~
Relisten swaps the old for new (￣▽￣)
No extra listeners piling up, silly thing ♡}

[coderabbitai]

Follow-up Comments

Add a repeated-listen case to the beforeExit listener test.

104-110: Trivial · Maintainability & Code Quality · Quick win

Add a repeated-listen case to the beforeExit listener test.

The new test calls listen(0) once, so it never reaches the branch that removes the previous beforeExit handler. If that removal is omitted, a second listen() on the same app leaves the first handler registered beside the new one. The existing assertions still pass in that case, so the regression is not detected. The current implementation removes the previous handler correctly, so this is a coverage gap rather than a production defect.

The suggested test calls listen(0) twice on one app and asserts one added listener. It then stops the first server directly, because the second listen() overwrites app.server. It calls app.stop() to remove the handler and stop the second server, and it asserts that the count returns to baseline.

Suggested test

 		expect(process.listeners('beforeExit').length).toBe(before)
 	})
+
+	it('keeps one beforeExit listener when listen is called again', async () => {
+		const before = process.listeners('beforeExit').length
+
+		const app = new Elysia().get('/health', () => 'hi')
+		app.listen(0)
+		const firstServer = app.server
+
+		app.listen(0)
+
+		expect(process.listeners('beforeExit').length).toBe(before + 1)
+
+		await firstServer?.stop()
+		await app.stop()
+
+		expect(process.listeners('beforeExit').length).toBe(before)
+	})
 })

Open the source location

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Review comment at @test/core/stop.test.ts around lines 104 - 110:
Add a repeated-listen case to the beforeExit listener test in stop.test.ts: call
listen twice on the same app and assert only one listener is added. Save the
first server before the second listen overwrites app.server, stop that server
directly, then call app.stop() and assert the listener count returns to
baseline.

---

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Commits

Reviewing files that changed from the base of the PR and between e037eca and b9b24a5.

Files selected for processing: 2

• src/adapter/bun/index.ts
• test/core/stop.test.ts

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