Ensure setAssetPrefix updates config instance

[ijjk]

This ensures we update nextConfig.assetPrefix instead of renderOpts as we aren't relying on renderOpts for these values anymore.

Closes: #82150

[vercel]

The setAssetPrefix method now sets nextConfig.assetPrefix instead of renderOpts.assetPrefix, but other parts of the codebase still expect renderOpts.assetPrefix to be available, causing asset prefix to not work correctly.

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Analysis

The change on line 1655 modified setAssetPrefix to update this.nextConfig.assetPrefix instead of this.renderOpts.assetPrefix. However, there are still two locations in the codebase that depend on renderOpts.assetPrefix:

1. packages/next/src/server/async-storage/work-store.ts line 129: assetPrefix: renderOpts?.assetPrefix || '',
2. packages/next/src/server/post-process.ts line 45: publicPath: \${renderOpts.assetPrefix}/_next/`,`

Both RenderOptsPartial interfaces in render.tsx and app-render/types.ts define assetPrefix?: string as an expected property. When setAssetPrefix is called during server initialization, the asset prefix will be stored in nextConfig but the code expecting it in renderOpts will receive undefined, potentially causing incorrect asset URLs or broken CSS optimization.

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Recommendation

The setAssetPrefix method should update both locations to maintain consistency. Change line 1655 to:

public setAssetPrefix(prefix?: string): void {
  const assetPrefix = prefix ? prefix.replace(/\/$/, '') : ''
  this.nextConfig.assetPrefix = assetPrefix
  this.renderOpts.assetPrefix = assetPrefix
}

Alternatively, if the intention is to only store it in nextConfig, then the code in work-store.ts and post-process.ts should be updated to read from nextConfig.assetPrefix instead of renderOpts.assetPrefix.

[ijjk]

The above referenced renderOpts.assetPrefix usage is derived from the new handlers interface which is not from the base-server renderOpts instance. This will be cleared up while deleting base-server code.

[huozhi]

We're still using renderOpts.assetPrefix here, do we still need to update the renderOpts.assetPrefix as well?

next.js/packages/next/src/server/post-process.ts

Line 45 in d8d5e9e

publicPath: `${renderOpts.assetPrefix}/_next/`,

[ijjk]

#82160 (comment)