[haranishi]

Pre-flight checklist

• The Contributing Guidelines on pull requests were checked during preparation.
• If this is a code change: I have written unit tests to verify the behavior.
• New API or substantial change: not applicable; this fixes typing for an existing documented option.

Motivation

A plugin returning the documented devServer: {open: '/docs'} configuration fails type checking when the consumer imports only Plugin from @docusaurus/types. The same configuration works at runtime. Importing webpack-dev-server elsewhere happens to hide the problem because it augments webpack.Configuration.

Load that augmentation from the public plugin declarations and declare the existing catalog dependency in @docusaurus/types. No runtime implementation or dependency versions change.

The regression test compiles an isolated TypeScript program, so imports in the monorepo cannot accidentally supply the missing augmentation. It checks returning and reading devServer, retaining Webpack and mergeStrategy options, and rejecting open: 42.

Test Plan

Tested on macOS with Node.js 26.13.0 and pnpm 12.3.4, against upstream c00f04e2376e057090d65d6bfb6a82d49ea3eca6.

• pnpm test __tests__/plugin-types.test.ts: passes. Before the declaration fix, the same test fails with missing devServer properties and an unused @ts-expect-error directive.
• pnpm build:packages: passes (36 packages), after clearing generated incremental build information.
• pnpm typecheck:tests: passes.
• pnpm --filter website typecheck: passes.
• pnpm lint: passes, including ESLint, Stylelint, spelling, catalogs, deduplication, Knip and formatting. ESLint reports existing warnings and no errors.
• pnpm test: 3,223 passed and 6 failed (205 test files passed, 1 failed).

Existing full-suite failures on the HFS+ checkout

All six failures are blog feed directory-tree snapshots in packages/docusaurus-plugin-content-blog/src/__tests__/feed.test.ts: the filesystem returns the decomposed spelling of héllô, while the snapshots contain its composed spelling.

Reverting the declaration fix and running pnpm test packages/docusaurus-plugin-content-blog/src/__tests__/feed.test.ts reproduces the same six failures (16 other tests pass). The original declaration was restored for that check and the fix restored afterwards. No blog files or snapshots are changed in this patch. The directory-tree normalization is addressed separately in #12937.

Test links

Deploy preview: https://deploy-preview-12935--docusaurus-2.netlify.app/.

The existing documented contract is Configuring dev server. This is a type-only fix; no UI changes.

Related issues/PRs

Fixes #9654.

AI assistance: this patch, regression test and draft description were prepared with Codex. Validation was run locally with Codex (AI-assisted); no independent human review is claimed.

Summary by CodeRabbit

• Improvements
  • Improved TypeScript support for webpack configuration, including development-server options, so invalid setting types can be flagged during development.

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[coderabbitai]

No actionable comments were generated in the recent review.

Walkthrough

The @docusaurus/types package now loads webpack-dev-server’s augmentation of webpack.Configuration. A fixture and strict TypeScript test check configureWebpack typing, including an expected error for a numeric devServer.open value.

Changes: configureWebpack type support

Layer / File(s)	Summary
Load the devServer augmentation packages/docusaurus-types/package.json, packages/docusaurus-types/src/plugin.d.ts	The types package adds webpack-dev-server as a dependency and imports it to load its webpack.Configuration augmentation.
Exercise configureWebpack types __tests__/__fixtures__/configureWebpack/index.ts, __tests__/plugin-types.test.ts	The fixture defines a configureWebpack callback with devServer settings and marks a numeric devServer.open value as an expected type error. The test checks the fixture with strict TypeScript compilation and expects no diagnostics.

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

Change: Bug fix · Severity of issue fixed: Low

Suggested labels: pr: bug fix

Merge Risk: Minimal · up to 0db25

No actionable merge-blocking risk is identified for the devServer typing change; it is mergeable after normal checks.

Pre-merge checks: 5

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly identifies the main change: loading webpack-dev-server configuration types for consumers of @docusaurus/types.
Linked Issues check		Issue #9654 requires configureWebpack to accept the documented devServer option. The PR loads webpack-dev-server's type augmentation from the public plugin declarations and adds its catalog depe…
Out of Scope Changes check		The declaration change, dependency declaration, fixture, and type-checking test all support the #9654 typing fix. The PR summary reports no runtime changes. The excluded pnpm-lock.yaml does not prov…
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 #9654 requires configureWebpack to accept the documented devServer option. The PR loads webpack-dev-server's type augmentation from the public plugin declarations and adds its catalog dependency. The isolated type test checks valid devServer settings and rejects open: 42, while retaining Webpack and mergeStrategy options.

Full details: Out of Scope Changes check

Explanation

The declaration change, dependency declaration, fixture, and type-checking test all support the #9654 typing fix. The PR summary reports no runtime changes. The excluded pnpm-lock.yaml does not provide evidence of an unrelated change.

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 3 files. (1 skipped: 1 unsupported.)

Finishing Touches

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Recent review info

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Commits

Reviewing files that changed from the base of the PR and between c00f04e and 0db258b.

Files ignored due to path filters: 1

• pnpm-lock.yaml is excluded by !**/pnpm-lock.yaml

Files selected for processing: 4

• __tests__/__fixtures__/configureWebpack/index.ts
• __tests__/plugin-types.test.ts
• packages/docusaurus-types/package.json
• packages/docusaurus-types/src/plugin.d.ts

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