[alexander-akait]

Summary

Fixes #5782

In plugin mode, a listen() failure (e.g. EADDRINUSE) was only logged from the done hook, so watch() callers never saw it and the build kept running with no server. The listen is still started once from the aggregate done, and is now awaited from each Compiler's async done hook: the compiler itself, or every child of a MultiCompiler (whose aggregate done fires inside the last child's done). The error now reaches the watch() callback and webpack stops watching, like start() rejecting.

Port already taken, compiler.watch({}, (err) => …):

	single Compiler	MultiCompiler
before	err is null, error only logged	err is null, error only logged
after	err.code === "EADDRINUSE"	err.code === "EADDRINUSE"

What kind of change does this PR introduce?

fix

Did you add tests for your changes?

Yes, test/e2e/api-plugin.test.js: "should propagate listen errors via the watch callback" for a single compiler and for a MultiCompiler, both with a real occupied port. They replace "should log a listen() failure instead of throwing", which asserted the old behavior.

Does this PR introduce a breaking change?

No. The error goes to the watch() callback instead of the logger.

If relevant, what needs to be documented once your changes are merged or what have you already documented?

n/a

Use of AI

Claude Code wrote the fix and the tests. It confirmed the new tests fail without the fix, and it ran test/e2e/api-plugin.test.js and npm run lint locally.

---

Generated by Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Plugin-mode server startup failures, including port conflicts, are now reported through the compiler’s watch callback instead of being logged while watching continues.
  • Shutdown now waits for pending setup and listening operations to finish.

[changeset-bot]

🦋 Changeset detected

Latest commit: 36debd1

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

This PR includes changesets to release 1 package

Name	Type
webpack-dev-server	Patch

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Commits

Reviewing files that changed from the base of the PR and between 3b613f4 and 36debd1.

Files selected for processing: 1

• test/e2e/api-plugin.test.js

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Walkthrough

In plugin mode, the server retains its setup-and-listen promise. Compiler done hooks await that promise and forward listen failures to the watch() callback. Tests cover port conflicts for single-compiler and MultiCompiler setups, and a patch changeset documents the behavior.

Priority: Normal

Severity of issue fixed: Medium

Merge Risk: Minimal · up to 36deb

Plugin listen failures are delivered through the watch callback as intended, and no merge-blocking risk is established.

Pre-merge checks: 5

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: propagating plugin-mode listen errors to the watch callback.
Linked Issues check		Issue #5782 requires plugin-mode listen failures to reach the watch() callback. lib/Server.js tracks the pending listen promise and awaits it from compiler done hooks, including MultiCompiler …
Out of Scope Changes check		The changes stay within issue #5782. lib/Server.js implements error propagation. test/e2e/api-plugin.test.js verifies the behavior. The changeset documents the fix. No unrelated change is identifi…
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: Linked Issues check

Explanation

Issue #5782 requires plugin-mode listen failures to reach the watch() callback. lib/Server.js tracks the pending listen promise and awaits it from compiler done hooks, including MultiCompiler children. The end-to-end tests cover both compiler setups with an occupied port and verify EADDRINUSE in the watch callback.

Full details: Out of Scope Changes check

Explanation

The changes stay within issue #5782. lib/Server.js implements error propagation. test/e2e/api-plugin.test.js verifies the behavior. The changeset documents the fix. No unrelated change is identified.

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.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.82%. Comparing base (9a6472e) to head (36debd1).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5787      +/-   ##
==========================================
+ Coverage   95.80%   95.82%   +0.02%     
==========================================
  Files           6        6              
  Lines        5551     5583      +32     
==========================================
+ Hits         5318     5350      +32     
  Misses        233      233              

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