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Walkthrough

The change modifies the ReplacePlugin in packages/vite/src/plugins/replace.ts to pass an additional options object when calling replacePlugin in the conditional branch where rolldownVersion is present. Specifically, it adds { preventAssignment: true } as a second argument to the function call, aligning the behaviour with the else branch that already includes this option via object spreading.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Rationale: This is a localised, single-file modification that adds consistent parameter passing across conditional branches. The change is straightforward—adding a configuration option to a function call—with no complex logic or architectural implications. The repetition of the same option across both branches reduces cognitive load for verification.

Pre-merge checks and finishing touches

Learnt from: TheAlexLichter
PR: nuxt/nuxt#31812
File: packages/nuxt/src/components/plugins/islands-transform.ts:202-202
Timestamp: 2025-04-18T18:33:41.753Z
Learning: In Nuxt, using `rolldownVersion` (not `rollupVersion`) is intentional when detecting if rolldown-vite is being used, even though TypeScript may show an error because the property isn't in standard type definitions yet.

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npm i https://pkg.pr.new/@nuxt/kit@33526

npm i https://pkg.pr.new/nuxt@33526

npm i https://pkg.pr.new/@nuxt/rspack-builder@33526

npm i https://pkg.pr.new/@nuxt/schema@33526

npm i https://pkg.pr.new/@nuxt/vite-builder@33526

npm i https://pkg.pr.new/@nuxt/webpack-builder@33526

commit: 0fccec7

CodSpeed Performance Report

Merging #33526 will not alter performance

_{Comparing TheAlexLichter-patch-1 (0fccec7) with main (b7ed1d3)¹}

Summary

✅ 10 untouched

thank you 🙏

@TheAlexLichter Out of interest I tried this fix via patching @nuxt/vite-builder myself and unfortunately it's still the same behaviour. Nuxt does not start correctly.

{
  'import.meta.dev': true,
  'import.meta.test': false,
  'import.meta.server': true,
  'import.meta.client': false,
  'import.meta.browser': false 
}

function replacePlugin(values = {}, options = {}) {
	let hasNonStringValues = false;
	Object.keys(values).forEach((key) => {
		const value = values[key];
		if (typeof value !== "string") {
            console.log(value);
			hasNonStringValues = true;
			values[key] = String(value);
		}
	});
	if (hasNonStringValues) logger.warn("Some values provided to `replacePlugin` are not strings. They will be converted to strings, but for better performance consider converting them manually.");
	return new BuiltinPlugin("builtin:replace", {
		...options,
		values
	});
}

@TheAlexLichter Out of interest I tried this fix via patching @nuxt/vite-builder myself and unfortunately it's still the same behaviour. Nuxt does not start correctly.
Edit: The following explanation is probably wrong since I assume the plugin works on source code (=text) level so replacing a string with a string is fine.

I had a quick look at the source code and I think the issue is the following:

The following object is passed to the replacePlugin config:

{
  'import.meta.dev': true,
  'import.meta.test': false,
  'import.meta.server': true,
  'import.meta.client': false,
  'import.meta.browser': false 
}

The replacePlugin function looks like this:

function replacePlugin(values = {}, options = {}) {
	let hasNonStringValues = false;
	Object.keys(values).forEach((key) => {
		const value = values[key];
		if (typeof value !== "string") {
            console.log(value);
			hasNonStringValues = true;
			values[key] = String(value);
		}
	});
	if (hasNonStringValues) logger.warn("Some values provided to `replacePlugin` are not strings. They will be converted to strings, but for better performance consider converting them manually.");
	return new BuiltinPlugin("builtin:replace", {
		...options,
		values
	});
}

In there all values of the object are converted to strings via String(value), so the boolean values are all strings now. This likely causes issues and would explain the Some values provided to replacePlugin are not strings warning.

In fact, the Rollup plugin does that already under the hood (converting values to strings), but without notifying you.

In fact, the Rollup plugin does that already under the hood (converting values to strings), but without notifying you.

Yes, my bad. I initially thought that maybe something like false === 'false' could be the cause for the issue, but then realized that the plugin probably treats the source code as text files and on that level everything is a string/text anyways.