i18n dynamic routes: build log differs from build output

[Because789]

Astro Info

Astro                    v4.5.12
Node                     v20.11.1
System                   Linux (x64)
Package Manager          pnpm
Output                   static
Adapter                  none
Integrations             @astrojs/mdx
                         @astrojs/tailwind
                         astro-icon

If this issue only occurs in one browser, which browser is a problem?

No response

Describe the Bug

I have the dynamic route src/pages/[...lang]/index.astro in my project (prefixDefaultLocale: false). It runs on dev server without any issues and builds correctly. But the build log shows that it generates the routes: /index.html, /en/index.html, /en/index.html and /en/en/index.html:

What's the expected result?

Show correct build output in logs.

Link to Minimal Reproducible Example

https://stackblitz.com/edit/withastro-astro-quy3ic?file=src%2Fpages%2F%5B...lang%5D%2Findex.astro

Participation

• I am willing to submit a pull request for this issue.

[1574242600]

Can you tell me why this is necessary?
which results in duplicate language prefix.

export function staticPathsLangParams() {
    const urls = getRelativeLocaleUrlList();
    return urls.map((url) => ({
        params: { lang: url === "/" ? undefined : url },
    }));
}

export const getStaticPaths = staticPathsLangParams;

As for not generating /en/en/index.html, it's because /en/index.html is considered the same path and is skipped.

astro/packages/astro/src/core/build/generate.ts

Lines 482 to 493 in 174ce25

	// Do not render the fallback route if there is already a translated page
	// with the same path
	if (
	route.type === 'fallback' &&
	// If route is index page, continue rendering. The index page should
	// always be rendered
	route.pathname !== '/' &&
	// Check if there is a translated page with the same path
	Object.values(options.allPages).some((val) => pathname.match(val.route.pattern))
	) {
	return;
	}

[ematipico]

This use case seems to be a bit of a stretch to me.

This use case uses an API to retrieve all the configured locales and generate pages from it. However, the project is configured to not prefix the default locale. The use case tries to build an invalid page on purpose.

I'm not sure what the correct way to go here is and what needs to be fixed.