Reviewing files that changed from the base of the PR and between d03b51e and c7417a8.

• packages/vite/src/vite-node.ts (6 hunks)

• GitHub Check: build
• GitHub Check: code

packages/vite/src/vite-node.ts (12)

13-13: LGTM!

The import of ViteNodeServer from vite-node/server is correctly added to support the new singleton pattern implementation.

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44-52: Excellent type safety improvements.

The new type definitions provide strong typing for socket request handling:

• RequestOf creates a mapped type ensuring each request has id, type, and payload fields
• ViteNodeRequest as a union type covers all possible request types
• This enforces compile-time type safety and prevents runtime errors

The implementation follows TypeScript best practices with proper mapped types and union types.

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232-244: Well-implemented singleton pattern with proper caching.

The singleton implementation provides several benefits:

• Caches the ViteNodeServer instance to avoid repeated instantiation
• Uses logical OR assignment (||=) for clean lazy initialisation
• Configuration looks appropriate with inline dependencies and SSR transform mode

The function signature is clear and the implementation is efficient.

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259-260: Strong typing improves request handling safety.

The function signature update to accept request: ViteNodeRequest provides compile-time type safety and better IDE support. This change aligns with the new type definitions and prevents potential runtime errors from malformed requests.

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261-261: Type-safe property access.

Using request.type instead of potentially unsafe property access ensures type safety and leverages the new ViteNodeRequest union type for proper type narrowing in the switch statement.

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264-264: Consistent use of numeric request IDs.

The change from string to numeric request IDs (request.id) is consistent across all response calls and aligns with the type definition where id: number. This ensures type safety and prevents potential serialisation issues.

Also applies to: 270-270, 279-279, 307-307

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274-274: Proper typed payload access.

Using request.payload for accessing request data ensures type safety and leverages TypeScript's type narrowing within each case block. The compiler can now verify that the correct payload structure is being accessed for each request type.

Also applies to: 283-283, 291-291

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278-278: Singleton server instance usage centralises module resolution.

Replacing direct access to ssrServer.pluginContainer and ssrServer.environments.ssr with the cached getNode(ssrServer) instance provides:

• Consistent server configuration across all operations
• Centralized instance management
• Better performance through caching

This aligns with the PR objective of using the Vite node server for transformations.

Also applies to: 286-287

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299-299: Enhanced error frame extraction.

Using node.transformRequest() for extracting error frames when parsing fails is a significant improvement. This provides better debugging information by attempting to transform the problematic module and including the transformed code in the error context.

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311-312: Proper handling of exhaustive switch with TypeScript annotation.

The @ts-expect-error comment correctly indicates that this default case should never be reached due to the exhaustive union type. The error message now uses the typed request.type property, maintaining type safety whilst providing meaningful error information.

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315-315: Consistent error handling with numeric ID.

Using request.id in error handling maintains consistency with the numeric ID type and ensures proper error response correlation.

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436-436: Function signatures updated for type consistency.

Both sendResponse and sendError functions now accept id: number instead of string, which:

• Maintains consistency with the ViteNodeRequest type definition
• Ensures type safety across the entire request/response flow
• Aligns with the JSON serialisation format

This change supports the overall type safety improvements in the file.

Also applies to: 461-461

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/vite-resolve