[wrangler] fix: handle deleted entry point during hot-reload without unhandled rejection

[matingathani]

Fixes #13122.

During wrangler dev, if the worker entry point is deleted or moved between builds, the readFileSync call inside the updateBundle callback throws synchronously and is promoted to an unhandled promise rejection, crashing the process.

Fix: Wrap the readFileSync call in a try/catch. On failure, log a warning and return the previous bundle unchanged, so the dev session stays alive.

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• Tests
  • Tests included/updated
• Public documentation
  • Documentation not necessary because: internal dev-mode error handling, no user-facing API change

[changeset-bot]

🦋 Changeset detected

Latest commit: fa47c9f

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
wrangler	Patch
@cloudflare/vite-plugin	Patch
@cloudflare/vitest-pool-workers	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[workers-devprod]

Codeowners approval required for this PR:

• ✅ @cloudflare/wrangler

Show detailed file reviewers

[Copilot]

Pull request overview

This PR improves wrangler dev hot-reload resilience by preventing a synchronous readFileSync() failure (when the worker entrypoint is deleted/moved between rebuilds) from being promoted into an unhandled promise rejection that crashes the process.

Changes:

• Wraps readFileSync(previousBundle.path, "utf8") in a try/catch during rebuild updates and logs a warning on failure.
• Skips applying the rebuild update when the entrypoint can’t be read (intended to keep the dev session alive).
• Adds a changeset to ship the fix as a patch release.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
packages/wrangler/src/dev/use-esbuild.ts	Adds error handling + warning log around reading the previous bundle entrypoint during rebuild updates.
.changeset/fix-unhandled-rejection-esbuild-entry-deleted.md	Declares a patch changeset describing the dev hot-reload crash fix.

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[matingathani]

@NuroDev @penalosa @dario-piotrowicz — all Copilot review comments have been addressed. This PR is ready for review.

[workers-devprod]

Codeowners reviews satisfied

[pkg-pr-new]

create-cloudflare

npm i https://pkg.pr.new/create-cloudflare@13838

@cloudflare/kv-asset-handler

npm i https://pkg.pr.new/@cloudflare/kv-asset-handler@13838

miniflare

npm i https://pkg.pr.new/miniflare@13838

@cloudflare/pages-shared

npm i https://pkg.pr.new/@cloudflare/pages-shared@13838

@cloudflare/unenv-preset

npm i https://pkg.pr.new/@cloudflare/unenv-preset@13838

@cloudflare/vite-plugin

npm i https://pkg.pr.new/@cloudflare/vite-plugin@13838

@cloudflare/vitest-pool-workers

npm i https://pkg.pr.new/@cloudflare/vitest-pool-workers@13838

@cloudflare/workers-editor-shared

npm i https://pkg.pr.new/@cloudflare/workers-editor-shared@13838

@cloudflare/workers-utils

npm i https://pkg.pr.new/@cloudflare/workers-utils@13838

wrangler

npm i https://pkg.pr.new/wrangler@13838

commit: fa47c9f

[matingathani]

The Windows CI failure is unrelated to this PR's changes.

What failed: packages/miniflare/test/plugins/browser/index.spec.ts — 9 browser plugin tests timed out or got SyntaxError: Unexpected token 'E', "Error: The"... is not valid JSON from entry.worker.js.

What this PR touches: only packages/wrangler/src/dev/use-esbuild.ts and a changeset file.

This looks like a known flaky Windows browser/CDP test (browser session not starting in time on slow Windows runners). Could a maintainer re-run the failed jobs? 🙏

[matingathani]

CI failure (Tests, Windows, packages-and-tools) is the same pre-existing miniflare browser plugin flake — browser session times out on the Windows runner. Unrelated to the hot-reload entrypoint fix. Could a maintainer re-run the failed job?