fix: correctly handle pathnames found in the `_redirects` file

[teemingc]

closes #9138

We need to add the pathnames found in the Cloudflare _redirects file to the exclude array so that they are handled by Cloudflare Pages rather than the Cloudflare Pages worker. This PR also adds the <redirects> directive so that it can be included manually in the exclude array in _routes.json.

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@sveltejs/adapter-cloudflare	Patch

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[benmccann]

I see this method is building a RoutesJSONSpec. Is that a structure that's expected by Cloudflare? If so, could you add a comment in the index.d.ts that points to the relevant Cloudflare docs?

[Rich-Harris]

preview: https://svelte-dev-git-preview-kit-12821-svelte.vercel.app/

this is an automated message

[teemingc]

Thanks, that's a good suggestion. I've added a link to the _routes.json documentation. 77dc208 (#12821)

[svelte-docs-bot[bot]]

Preview: https://svelte-dev-git-preview-kit-12821-svelte.vercel.app/

[teemingc]

Is this still all correct now that there was a breaking change about the other things that no longer are in the static directory?

Thanks for the reminder. I did a bit of refactoring and added a test for the _routes.json file generation. This should now correctly exclude redirects found during prerender (which were already being added to the _redirects file but did nothing because they weren't excluded).

I've also added a check in case someone added their _routes.json to the /static folder. It would have been overwritten anyway by our own _routes.json generated file but this makes it clearer that they should configure it through the adapter options.

The _route.json file generation also uses a set now so that we don't end up with any duplicate excluded routes. I've also added tests for the utility method.