fix: silent IMPORT_IS_UNDEFINED for proxy.ts

[hyoban]

[IMPORT_IS_UNDEFINED] Warning: Import `default` will always be undefined because there is no matching export in 'proxy.ts'
      ╭─[ \0virtual:vinext-rsc-entry:2632:34 ]
      │
 2632 │     ? (middlewareModule.proxy ?? middlewareModule.default)
      │                                  ────────────┬───────────  
      │                                              ╰───────────── 
──────╯

[pkg-pr-new]

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npm i https://pkg.pr.new/vinext@787

commit: c760b3b

[james-elicx]

/bigbonk review

[ask-bonk]

Good fix for a real annoyance. The approach is correct — suppressing bundler noise for known-safe generated patterns. Two issues worth addressing:

1. Missing .tsx/.jsx extensions — findMiddlewareFile() iterates all pageExtensions (default: tsx, ts, jsx, js), so a user with proxy.tsx or middleware.jsx would still see the warning. The filter should cover all possible extensions, or match more broadly.

2. Named export warnings not covered — The generated entry code does middlewareModule.proxy ?? middlewareModule.default (or .middleware ?? .default). When a file only exports default, the bundler can also warn about Import \proxy` will always be undefined(and vice versa). The current filter only matchesImport `default``, missing the symmetric case.

[ask-bonk]

This only covers .ts and .js, but findMiddlewareFile() iterates all fileMatcher.dottedExtensions which defaults to [".tsx", ".ts", ".jsx", ".js"] (and can include custom extensions via pageExtensions config). A user with proxy.tsx or middleware.jsx would still see the warning.

Consider matching on just the basename without extension, e.g.:

Suggested change

	warning.message?.includes("middleware.js")) &&
	if (
	warning.code === "IMPORT_IS_UNDEFINED" &&
	(warning.message?.includes("virtual:vinext-rsc-entry") ||
	warning.message?.includes("virtual:vinext-server-entry")) &&
	/Import `(?:default|proxy|middleware)` will always be undefined/.test(
	warning.message ?? "",
	) &&
	/\b(?:proxy|middleware)\.\w+/.test(warning.message ?? "")
	) {

This also covers the symmetric case where the named export (proxy or middleware) triggers the warning instead of default (e.g., when the file only has a default export, middlewareModule.proxy is undefined).

[ask-bonk]

The test message strings use \\n (literal backslash-n) instead of \n (actual newline). In real Rolldown output the message would contain an actual newline character. This doesn't affect correctness since .includes() would match either way in this test, but it's slightly misleading.

Also, consider adding test cases for:

• .tsx/.jsx extensions (proxy.tsx, middleware.jsx)
• Named export warnings (Import \proxy` will always be undefined`)
• The symmetric case where only a default export exists

[ask-bonk]

Review posted successfully. Here's a summary of the feedback:

PR #787 suppresses noisy IMPORT_IS_UNDEFINED warnings for proxy.ts/middleware.ts default export fallbacks in generated virtual entries. The fix is correct in approach, but has two gaps:

1. Missing .tsx/.jsx extensions — The filter only matches .ts and .js, but findMiddlewareFile() scans all pageExtensions (default: tsx, ts, jsx, js). Users with proxy.tsx or middleware.jsx would still see the warning. Suggested using a regex like /\b(?:proxy|middleware)\.\w+/ to match any extension.

2. Named export warnings not covered — The generated code does middlewareModule.proxy ?? middlewareModule.default. When a file only has a default export, the bundler can also warn about Import \proxy` will always be undefined(the symmetric case). The current filter only matchesImport `default`. Suggested broadening to match Import `(?:default|proxy|middleware)``.

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